{"id":1282,"date":"2025-10-17T14:32:08","date_gmt":"2025-10-17T21:32:08","guid":{"rendered":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/?page_id=1282"},"modified":"2026-04-06T10:56:52","modified_gmt":"2026-04-06T17:56:52","slug":"chapter-11-herbaceous-landscape-plants","status":"publish","type":"page","link":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/chapter-11-herbaceous-landscape-plants\/","title":{"rendered":"Chapter 11: Herbaceous Landscape Plants"},"content":{"rendered":"<div class=\"wsu-hero wsu-width--full wsu-pattern--wsu-light-radial-left  wsu-hero--style-boxed \">\n\t<div class=\"wsu-hero__background\">\n\t\t<div class=\"wsu-image-frame wsu-image-frame--fill\">\n\t<img decoding=\"async\" src=\"https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/09\/AdobeStock_145658897.jpg\"\n\t\tsrcset=\"https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/09\/AdobeStock_145658897.jpg 1223w, https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/09\/AdobeStock_145658897.jpg 300w, https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/09\/AdobeStock_145658897.jpg 1024w, https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/09\/AdobeStock_145658897.jpg 768w\"\n\t\tsizes=\"(max-width: 1223px) 100vw, 1223px\"\n\t\talt=\"Woman planting colorful spring flowers in yard.\"\n\t\tstyle=\"object-position: 71% 85%\"\n\t\t\/>\n<\/div>\n\t<\/div>\n\t<div class=\"wsu-hero__overlay\">\n\t<\/div>\n\t<div class=\"wsu-hero__content-wrapper\">\n\t\t<div class=\"wsu-hero__inner-content-wrapper\">\n\t\t\t\t\t\t<div class=\"wsu-hero__title-wrapper\">\n\t\t\t\t<h1 class=\"wsu-hero__title\">Herbaceous<br>Landscape Plants<\/h1>\t\t\t\t<div class=\"wsu-hero__caption\">Chapter 11<\/div>\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<div class=\"wsu-hero__content\">\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n\n\n\n<p class=\"wsu-max-width--hero wsu-spacing-after--xsmall\"><strong>Jim Kropf<\/strong>, Pierce County Extension Director, Agricultural and Natural Resources Unit, Washington State University<\/p>\n\n\n\n<div style=\"height:10px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n<div class=\"wsu-row wsu-row--sidebar-right\" >\r\n    \n<div class=\"wsu-column\"  style=\"\">\r\n\t\n\n<h2 class=\"wp-block-heading wsu-font-size--xlarge wsu-heading--style-marked wsu-spacing-after--xxmedium\" id=\"learning-objectives\">Learning Objectives<\/h2>\n\n\n\n<ul>\n<li>Understand life cycles of annuals, biennials, and perennials and how those life cycles affect a plant\u2019s garden usefulness. <\/li>\n\n\n\n<li>Understand how climate and hardiness affect success of plants.<\/li>\n\n\n\n<li>Understand principles of basic care and maintenance realities.<\/li>\n\n\n\n<li>Identify and manage common garden problems.<\/li>\n\n\n\n<li>Understand garden requirements and maintenance techniques for several speci\ufb01c types of herbaceous perennials.<\/li>\n<\/ul>\n\n<\/div>\r\n\n\n<div class=\"wsu-column\"  style=\"\">\r\n\t\n\n<h2 class=\"wp-block-heading\">Topics Covered<\/h2>\n\n\n\n<ul class=\"wsu-menu--style-sidebar\">\n<li><a href=\"#ch11-climate-zones\" data-type=\"internal\" data-id=\"#ch11-climate-zones\">Herbaceous Plants in the Landscape<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-herbaceous-plant-life-cycles\" data-type=\"internal\" data-id=\"#ch11-herbaceous-plant-life-cycles\">Herbaceous Plant Life Cycles<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-climate-zones\" data-type=\"internal\" data-id=\"#ch11-climate-zones\">Climate and USDA Temperature Zones<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-plant-selection\" data-type=\"internal\" data-id=\"#ch11-plant-selection\">Plant Selection<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-maintenance\" data-type=\"internal\" data-id=\"#ch11-maintenance\">Maintenance<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-common-problems\" data-type=\"internal\" data-id=\"#ch11-common-problems\">Common Problems<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-specific-garden-styles\" data-type=\"internal\" data-id=\"#ch11-specific-garden-styles\">Specific Garden Styles<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-specific-garden-plants\" data-type=\"internal\" data-id=\"#ch11-specific-garden-plants\">Specific Garden Plants<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-learning-more\" data-type=\"internal\" data-id=\"#ch11-learning-more\">Learning More<\/a><\/li>\n\n\n\n<li><a href=\"#ch11-further-reading\" data-type=\"internal\" data-id=\"#ch11-further-reading\">Further Reading<\/a><\/li>\n<\/ul>\n\n<\/div>\r\n\n<\/div>\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-climate-zones\">Herbaceous Plants in the Landscape<\/h2>\n\n\n\n<p>Trends and styles in gardening may vary from year to year, but the basic delight gardeners find in the details and presence of plants remains constant. The term \u201cornamental gardening\u201d now seems outdated; plants are often chosen for their contribution to the ecology of the garden as well as for their appearance. They help conserve water, attract and feed beneficial insects, and are suited to the individual garden\u2019s <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#m\" data-type=\"URL\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>microclimate<\/strong> (opens in new window)<\/a>. Edibles may also be combined with the landscape. As you wander nurseries and plant sales looking at choices, you should consider much more than the plant\u2019s form and color.<\/p>\n\n\n\n<p>Tucked under trees and shrubs, or edging a small lawn, brightening an entryway, or acting as an elegant ground cover, herbaceous plants give the garden its texture. Without them, gardens lack interest. Gardeners often comment about seeing \u201csterile\u201d landscapes composed of large square footage of bark, a few shrubs, and one tree\u2014a style often seen around newly constructed houses. Herbaceous plants, from hardy ferns to wispy, annual poppies, provide the missing element in the landscape. The most monotonous garden will provide year-round interest when <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#h\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>herbaceous perennials<\/strong> (opens in new window)<\/a> are properly chosen and placed in the landscape.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Know Your Plants\u2019 Species<\/em><\/h3>\n\n\n\n<p>Learn the species of plants you have or that you wish to grow. <em>Iris germanica<\/em>, the common German \u201cbearded\u201d iris, grows well in full sun, requires little extra irrigation in summer, and prefers a pH of 6.5\u20137.5. However, <em>Iris ensata<\/em>, the Japanese iris, grows best in acidic soil (pH 5.5\u20136.0) with continuous moisture. Japanese iris can thrive on the edges of ponds in partial shade. These two irises share a genus, but the two different species require nearly opposite garden conditions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"ch11-herbaceous-plant-life-cycles\"><em>Herbaceous Plant Life Cycles<\/em><\/h2>\n\n\n\n<p>Herbaceous plants are those that do not retain woody stems. They may have a life cycle that is perennial, biennial, or annual. Knowing the basic life cycles of herbaceous plants helps plan for the seasonal progression of a garden.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Perennials<\/em><\/h3>\n\n\n\n<p class=\"wsu-spacing-after--xsmall\">Herbaceous perennials exist worldwide in great variety in temperate zones. The key to their life cycle is the seasonal change in temperatures, resulting in varying growth habits. In general, herbaceous perennials:<\/p>\n\n\n\n<ul>\n<li>generally go dormant during cold weather\u2014the current season\u2019s foliage dies.<\/li>\n\n\n\n<li>do not form a permanent woody structure.<\/li>\n\n\n\n<li>may be grown for foliage only (<em>Hosta<\/em> spp.) or for bloom.<\/li>\n\n\n\n<li>have a limited bloom period: short (less than one week, as with some peonies) to long (six weeks or more, as with yarrow, <em>Achillea<\/em> spp.).<\/li>\n\n\n\n<li>may be short-lived (three years, as with wallflowers, <em>Erysimum<\/em> spp.) or long-lived (decades, as with <em>Paeonia lactiflora<\/em> and hybrids).<\/li>\n<\/ul>\n\n\n\n<p>Perennials take time to establish, at least two years. There is an often-quoted saying: \u201cThe first year, they sleep; the next year, they creep; the third year, they leap.\u201d Plants may be small initially, but a four-inch-potted plant will expand after two to three years to cover two or more square feet, depending on the plant.<\/p>\n\n\n\n<p>If you have time to allow for growth, buying smaller herbaceous perennials is more economical. For plants with fibrous roots, like asters (<em>Aster<\/em> \u00d7 <em>frikartii<\/em>) and Shasta daisies (<em>Leucanthemum<\/em> \u00d7 <em>superbum<\/em>) that will eventually form mats, it is good form to plant three of a type in a triangle with about 18 inches between plants. Other types that will be sculptural or add a spot of height, such as biennial mullein (<em>Verbascum<\/em> spp.), may be planted singly. Perennial gardens have no \u201cend date\u201d but are constantly being planted, redesigned, and replanted.<\/p>\n\n\n\n<p>This chapter will concentrate on plants hardy even in the colder zones of Washington, zones 4\u20136. These plants will also thrive in zones 7\u20138. In milder zones you will be able to use plants such as tender salvia (<em>Salvia guaranitica<\/em>) which do not survive winters in the coldest areas.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Biennials<\/em><\/h3>\n\n\n\n<p>Biennials develop small plants the first year; after going through a cold dormant period (winter), they bloom and set seed the next year.<\/p>\n\n\n\n<p>Planning gardens to include biennials requires allowing them space during the first year for their necessary development.<\/p>\n\n\n\n<p>Biennials are easy to forget during their first season, as they may lack garden presence, forming rosettes or other small ground level plants which disappear behind taller plants. Their second year brings colorful flowers, often on tall stems, such as with hollyhock (<em>Alcea rosea<\/em>). If you do not wish a flurry of new plants from seed, remove blooms from biennials before they mature. Many biennials produce thousands of seeds per plant and can become invasive outside of the garden.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Annuals<\/em><\/h3>\n\n\n\n<p>Annual plants complete their life cycle in one year, from seed germination to maturity. Annuals often produce ample seeds and reappear yearly from seed, leading gardeners to mistake them for herbaceous perennials (e.g., California poppy, <em>Eschscholzia californica<\/em>).<\/p>\n\n\n\n<p>Annuals provide long periods of bloom color, longer than most herbaceous perennials, if the fading flowers are picked off (deadheaded) so that the plant does not set seed. They are often featured in landscape situations requiring eye-catching, persistent summer color. See Table 1 for a list of common annuals for your garden in Washington.<\/p>\n\n\n\n<p class=\"wsu-spacing-after--large\">Some plants, such as tender geranium (<em>Pelargonium<\/em> spp.), act as perennials in warmer zones such as 9\u201310. Gardeners in Washington consider them annuals because they are killed by frost, but if sheltered throughout winter, they may live for years, gradually growing larger. Gardeners often overwinter plants, such as rose-scented geraniums (<em>Pelargonium capitatum<\/em>), by bringing them inside and treating them as houseplants. These plants are not strictly annuals because they do not mature in one season.<\/p>\n\n\n<span id=\"tablepress-80-description\" class=\"tablepress-table-description tablepress-table-description-id-80\">Table 1. Common annual species, weeks from seeding to transplant, mature height, and \ufb02ower color.<\/span>\n\n<table id=\"tablepress-80\" class=\"tablepress tablepress-id-80\" aria-describedby=\"tablepress-80-description\">\n<thead>\n<tr class=\"row-1 odd\">\n\t<th class=\"column-1\">Common name<\/th><th class=\"column-2\">Scientific name<\/th><th class=\"column-3\">Time from sowing<br \/>\nseeds indoors to transplanting<br \/>\n(weeks)*<\/th><th class=\"column-4\">Mature plant<br \/>\nheight (inches)<\/th><th class=\"column-5\">Flower color<\/th>\n<\/tr>\n<\/thead>\n<tbody class=\"row-hover\">\n<tr class=\"row-2 even\">\n\t<td class=\"column-1\">Ageratum<\/td><td class=\"column-2\"><i>Ageratum houstonianum<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">6\u201312<\/td><td class=\"column-5\">Blue, white, lavender, pink<\/td>\n<\/tr>\n<tr class=\"row-3 odd\">\n\t<td class=\"column-1\">Annual phlox<\/td><td class=\"column-2\"><i>Phlox drummondii<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">6\u201318<\/td><td class=\"column-5\">White, pink, purple, red, blue<\/td>\n<\/tr>\n<tr class=\"row-4 even\">\n\t<td class=\"column-1\">Begonia, wax leaf<\/td><td class=\"column-2\"><i>Begonia \u00d7 semperflorens-cultorum<\/i><\/td><td class=\"column-3\">12\u201316<\/td><td class=\"column-4\">6\u20138<\/td><td class=\"column-5\">Red, white, pink<\/td>\n<\/tr>\n<tr class=\"row-5 odd\">\n\t<td class=\"column-1\">Black-eyed Susan vine<\/td><td class=\"column-2\"><i>Thunbergia alata<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">72 (vine)<\/td><td class=\"column-5\">Orange, yellow, white<\/td>\n<\/tr>\n<tr class=\"row-6 even\">\n\t<td class=\"column-1\">Blanket flower<\/td><td class=\"column-2\"><i>Gaillardia pulchella<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Red, yellow, orange<\/td>\n<\/tr>\n<tr class=\"row-7 odd\">\n\t<td class=\"column-1\">Celosia, crested<\/td><td class=\"column-2\"><i>Celosia cristata<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Yellow, orange, pink, red<\/td>\n<\/tr>\n<tr class=\"row-8 even\">\n\t<td class=\"column-1\">Celosia, plumed<\/td><td class=\"column-2\"><i>Celosia plumosa<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">10\u201312<\/td><td class=\"column-5\">Yellow, orange, pink, red<\/td>\n<\/tr>\n<tr class=\"row-9 odd\">\n\t<td class=\"column-1\">China aster<\/td><td class=\"column-2\"><i>Callistephus chinensis<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Red, pink, blue, white, purple<\/td>\n<\/tr>\n<tr class=\"row-10 even\">\n\t<td class=\"column-1\">China pink<\/td><td class=\"column-2\"><i>Dianthus chinensis<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">6\u201312<\/td><td class=\"column-5\">Pink, white, red<\/td>\n<\/tr>\n<tr class=\"row-11 odd\">\n\t<td class=\"column-1\">Coleus<\/td><td class=\"column-2\"><i>Coleus \u00d7 hybridus<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">8\u201320<\/td><td class=\"column-5\">Red, pink, green, cream, yellow foliage<\/td>\n<\/tr>\n<tr class=\"row-12 even\">\n\t<td class=\"column-1\">Cornflower<\/td><td class=\"column-2\"><i>Centaurea cyanus<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">12\u201330<\/td><td class=\"column-5\">Pink, white, blue<\/td>\n<\/tr>\n<tr class=\"row-13 odd\">\n\t<td class=\"column-1\">Cosmos<\/td><td class=\"column-2\"><i>Cosmos bipinnatus<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">36\u201348<\/td><td class=\"column-5\">Pink, white, rose<\/td>\n<\/tr>\n<tr class=\"row-14 even\">\n\t<td class=\"column-1\">Cosmos, yellow<\/td><td class=\"column-2\"><i>Cosmos sulphureus<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">12\u201336<\/td><td class=\"column-5\">Yellow, orange, red<\/td>\n<\/tr>\n<tr class=\"row-15 odd\">\n\t<td class=\"column-1\">Dahlia, annual<\/td><td class=\"column-2\"><i>Dahlia hybrids<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201336<\/td><td class=\"column-5\">White, red, orange, pink, cream<\/td>\n<\/tr>\n<tr class=\"row-16 even\">\n\t<td class=\"column-1\">Dusty miller<\/td><td class=\"column-2\"><i>Senecio cineraria<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">8\u201316<\/td><td class=\"column-5\">Silvery-white foliage<\/td>\n<\/tr>\n<tr class=\"row-17 odd\">\n\t<td class=\"column-1\">Flowering cabbage\/kale<\/td><td class=\"column-2\"><i>Brassica oleracea<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">Pink, purple, cream foliage<\/td>\n<\/tr>\n<tr class=\"row-18 even\">\n\t<td class=\"column-1\">Forget-me-not<\/td><td class=\"column-2\"><i>Myosotis sylvatica<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">6\u201312<\/td><td class=\"column-5\">Blue, white<\/td>\n<\/tr>\n<tr class=\"row-19 odd\">\n\t<td class=\"column-1\">Four o\u2019clock<\/td><td class=\"column-2\"><i>Mirabilis jalapa<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">24\u201336<\/td><td class=\"column-5\">Pink, white, yellow, red<\/td>\n<\/tr>\n<tr class=\"row-20 even\">\n\t<td class=\"column-1\">Gazania<\/td><td class=\"column-2\"><i>Gazania rigens<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">6\u201312<\/td><td class=\"column-5\">Red, yellow, orange, white, pink<\/td>\n<\/tr>\n<tr class=\"row-21 odd\">\n\t<td class=\"column-1\">Geranium<\/td><td class=\"column-2\"><i>Pelargonium \u00d7 hortorum<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">Red, white, salmon, pink<\/td>\n<\/tr>\n<tr class=\"row-22 even\">\n\t<td class=\"column-1\">Globe amaranth<\/td><td class=\"column-2\"><i>Gomphrena globosa<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">White, pink, purple, red<\/td>\n<\/tr>\n<tr class=\"row-23 odd\">\n\t<td class=\"column-1\">Godetia<\/td><td class=\"column-2\"><i>Clarkia amoena<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">24\u201336<\/td><td class=\"column-5\">White, pink, red<\/td>\n<\/tr>\n<tr class=\"row-24 even\">\n\t<td class=\"column-1\">Heliotrope<\/td><td class=\"column-2\"><i>Heliotropium arborescens<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">White, blue, purple<\/td>\n<\/tr>\n<tr class=\"row-25 odd\">\n\t<td class=\"column-1\">Impatiens<\/td><td class=\"column-2\"><i>Impatiens walleriana<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">8\u201324<\/td><td class=\"column-5\">Red, pink, white, orange, lavender<\/td>\n<\/tr>\n<tr class=\"row-26 even\">\n\t<td class=\"column-1\">Larkspur<\/td><td class=\"column-2\"><i>Consolida ambigua<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">18\u201330<\/td><td class=\"column-5\">Blue, pink, white, rose<\/td>\n<\/tr>\n<tr class=\"row-27 odd\">\n\t<td class=\"column-1\">Lisianthus<\/td><td class=\"column-2\"><i>Eustoma grandiflorum<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Blue, pink, white, cream, rose<\/td>\n<\/tr>\n<tr class=\"row-28 even\">\n\t<td class=\"column-1\">Lobelia<\/td><td class=\"column-2\"><i>Lobelia erinus<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">6\u20138<\/td><td class=\"column-5\">Blue, violet, white, pink<\/td>\n<\/tr>\n<tr class=\"row-29 odd\">\n\t<td class=\"column-1\">Love-in-a-mist<\/td><td class=\"column-2\"><i>Nigella damascena<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">8\u201320<\/td><td class=\"column-5\">Blue, white, pink, purple<\/td>\n<\/tr>\n<tr class=\"row-30 even\">\n\t<td class=\"column-1\">Love-lies-bleeding<\/td><td class=\"column-2\"><i>Amaranthus caudatus<\/i><\/td><td class=\"column-3\">3\u20134<\/td><td class=\"column-4\">36\u201360<\/td><td class=\"column-5\">Red, red and green<\/td>\n<\/tr>\n<tr class=\"row-31 odd\">\n\t<td class=\"column-1\">Lupine<\/td><td class=\"column-2\"><i>Lupinus hartwegii<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">24\u201336<\/td><td class=\"column-5\">White, rose, red, purple<\/td>\n<\/tr>\n<tr class=\"row-32 even\">\n\t<td class=\"column-1\">Marigold, African<\/td><td class=\"column-2\"><i>Tagetes erecta<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">12\u201336<\/td><td class=\"column-5\">Yellow, orange, red<\/td>\n<\/tr>\n<tr class=\"row-33 odd\">\n\t<td class=\"column-1\">Marigold, French<\/td><td class=\"column-2\"><i>Tagetes patula<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">6\u201318<\/td><td class=\"column-5\">Yellow, orange, red<\/td>\n<\/tr>\n<tr class=\"row-34 even\">\n\t<td class=\"column-1\">Mexican sunflower<\/td><td class=\"column-2\"><i>Tithonia rotundifolia<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">48\u201372<\/td><td class=\"column-5\">Orange<\/td>\n<\/tr>\n<tr class=\"row-35 odd\">\n\t<td class=\"column-1\">Monkey flower<\/td><td class=\"column-2\"><i>Mimulus \u00d7 hybridus<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">6\u201312<\/td><td class=\"column-5\">Yellow, red, orange<\/td>\n<\/tr>\n<tr class=\"row-36 even\">\n\t<td class=\"column-1\">Moss rose<\/td><td class=\"column-2\"><i>Portulaca grandiflora<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">6\u20138<\/td><td class=\"column-5\">Yellow, white, rose, orange, pink, red<\/td>\n<\/tr>\n<tr class=\"row-37 odd\">\n\t<td class=\"column-1\">Nasturtium<\/td><td class=\"column-2\"><i>Tropaeolum majus<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12<\/td><td class=\"column-5\">Yellow, orange, red, cream<\/td>\n<\/tr>\n<tr class=\"row-38 even\">\n\t<td class=\"column-1\">Nicotiana<\/td><td class=\"column-2\"><i>Nicotiana alata<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">18\u201336<\/td><td class=\"column-5\">Red, pink, white, purple<\/td>\n<\/tr>\n<tr class=\"row-39 odd\">\n\t<td class=\"column-1\">Painted tongue<\/td><td class=\"column-2\"><i>Salpiglossis sinuata<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">24\u201336<\/td><td class=\"column-5\">Pink, yellow, red, purple, white<\/td>\n<\/tr>\n<tr class=\"row-40 even\">\n\t<td class=\"column-1\">Pansy<\/td><td class=\"column-2\"><i>Viola \u00d7 wittrockiana<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">6\u20138<\/td><td class=\"column-5\">Blue, purple, white, yellow, orange, pink<\/td>\n<\/tr>\n<tr class=\"row-41 odd\">\n\t<td class=\"column-1\">Petunia<\/td><td class=\"column-2\"><i>Petunia \u00d7 hybrida<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">12\u201336<\/td><td class=\"column-5\">White, pink, purple, red<\/td>\n<\/tr>\n<tr class=\"row-42 even\">\n\t<td class=\"column-1\">Poppy, California<\/td><td class=\"column-2\"><i>Eschscholzia californica<\/i><\/td><td class=\"column-3\">2\u20133<\/td><td class=\"column-4\">12<\/td><td class=\"column-5\">Red, yellow, pink, white<\/td>\n<\/tr>\n<tr class=\"row-43 odd\">\n\t<td class=\"column-1\">Poppy, Iceland<\/td><td class=\"column-2\"><i>Papaver nudicaule<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">White, yellow, orange, red<\/td>\n<\/tr>\n<tr class=\"row-44 even\">\n\t<td class=\"column-1\">Pot marigold<\/td><td class=\"column-2\"><i>Calendula officinalis<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Yellow, orange<\/td>\n<\/tr>\n<tr class=\"row-45 odd\">\n\t<td class=\"column-1\">Sage, mealycup<\/td><td class=\"column-2\"><i>Salvia farinacea<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">18\u201324<\/td><td class=\"column-5\">Blue, white<\/td>\n<\/tr>\n<tr class=\"row-46 even\">\n\t<td class=\"column-1\">Sage, scarlet<\/td><td class=\"column-2\"><i>Salvia splendens<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Red, white, purple, salmon<\/td>\n<\/tr>\n<tr class=\"row-47 odd\">\n\t<td class=\"column-1\">Snapdragon<\/td><td class=\"column-2\"><i>Antirrhinum majus<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">6\u201318<\/td><td class=\"column-5\">Yellow, orange, red, white, pink<\/td>\n<\/tr>\n<tr class=\"row-48 even\">\n\t<td class=\"column-1\">Spider flower<\/td><td class=\"column-2\"><i>Cleome hassleriana<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">48<\/td><td class=\"column-5\">White, purple, rose<\/td>\n<\/tr>\n<tr class=\"row-49 odd\">\n\t<td class=\"column-1\">Statice<\/td><td class=\"column-2\"><i>Limonium sinuatum<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201324<\/td><td class=\"column-5\">Yellow, pink, white, blue, purple, apricot<\/td>\n<\/tr>\n<tr class=\"row-50 even\">\n\t<td class=\"column-1\">Strawflower<\/td><td class=\"column-2\"><i>Xerochrysum bracteatum<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">18\u201336<\/td><td class=\"column-5\">White, red, pink, yellow, rose, orange<\/td>\n<\/tr>\n<tr class=\"row-51 odd\">\n\t<td class=\"column-1\">Stock<\/td><td class=\"column-2\"><i>Matthiola incana<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">30\u201345<\/td><td class=\"column-5\">White, yellow, apricot, blue, pink, red<\/td>\n<\/tr>\n<tr class=\"row-52 even\">\n\t<td class=\"column-1\">Swan River daisy<\/td><td class=\"column-2\"><i>Brachycome iberidifolia<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">Blue, purple, pink, white<\/td>\n<\/tr>\n<tr class=\"row-53 odd\">\n\t<td class=\"column-1\">Sunflower<\/td><td class=\"column-2\"><i>Helianthus annuus<\/i><\/td><td class=\"column-3\">2\u20133<\/td><td class=\"column-4\">24\u2013108<\/td><td class=\"column-5\">Yellow, red, bronze, orange<\/td>\n<\/tr>\n<tr class=\"row-54 even\">\n\t<td class=\"column-1\">Sweet alyssum<\/td><td class=\"column-2\"><i>Lobularia maritima<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">4\u20138<\/td><td class=\"column-5\">White, purple, pink<\/td>\n<\/tr>\n<tr class=\"row-55 odd\">\n\t<td class=\"column-1\">Sweet pea<\/td><td class=\"column-2\"><i>Lathyrus odoratus<\/i><\/td><td class=\"column-3\">6\u20138<\/td><td class=\"column-4\">72 (vine)<\/td><td class=\"column-5\">Orange, yellow, rose, purple, white<\/td>\n<\/tr>\n<tr class=\"row-56 even\">\n\t<td class=\"column-1\">Sweet William<\/td><td class=\"column-2\"><i>Dianthus barbatus<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">Red, pink, white<\/td>\n<\/tr>\n<tr class=\"row-57 odd\">\n\t<td class=\"column-1\">Torenia<\/td><td class=\"column-2\"><i>Torenia fournieri<\/i><\/td><td class=\"column-3\">8\u201310<\/td><td class=\"column-4\">8\u201312<\/td><td class=\"column-5\">Blue, purple, pink<\/td>\n<\/tr>\n<tr class=\"row-58 even\">\n\t<td class=\"column-1\">Verbena<\/td><td class=\"column-2\"><i>Glandularia \u00d7 hybrida<\/i><\/td><td class=\"column-3\">8\u201312<\/td><td class=\"column-4\">8\u201324<\/td><td class=\"column-5\">White, pink, blue, red<\/td>\n<\/tr>\n<tr class=\"row-59 odd\">\n\t<td class=\"column-1\">Vinca, annual<\/td><td class=\"column-2\"><i>Catharanthus roseus<\/i><\/td><td class=\"column-3\">10\u201312<\/td><td class=\"column-4\">12\u201318<\/td><td class=\"column-5\">White, pink, red<\/td>\n<\/tr>\n<tr class=\"row-60 even\">\n\t<td class=\"column-1\">Zinnia, narrowleaf<\/td><td class=\"column-2\"><i>Zinnia angustifolia<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">8\u201312<\/td><td class=\"column-5\">Orange, white, yellow<\/td>\n<\/tr>\n<tr class=\"row-61 odd\">\n\t<td class=\"column-1\">Zinnia, common<\/td><td class=\"column-2\"><i>Zinnia elegans<\/i><\/td><td class=\"column-3\">4\u20136<\/td><td class=\"column-4\">12\u201336<\/td><td class=\"column-5\">Red, pink, yellow, orange, white<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-80 from cache -->\n\n\n\n<p class=\"wsu-font-size--small wsu-max-width--hero wsu-spacing-after--large\"><em>Source<\/em>: Table 1 courtesy of Teresa Cerny-Koenig, Washington State University, Pullman, Washington and Richard and Jo Cerny, Spring Valley Farm, Cobden, Illinois.<br>* Contact your local WSU Extension office for information on the last average frost date in your area.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\">Climate and USDA Temperature Zones<\/h2>\n\n\n\n<p>Two factors primarily influence plant growth and survival in Washington State: temperature variations from season to season and available rainfall. Of these two, it is somewhat easier to plan for temperature variations, because plants can be chosen to suit temperature ranges by understanding the zone of the garden and matching it to available plant hardiness information. Occasionally, a winter with below-average temperatures will confound the best zonal planning and result in plant losses.<\/p>\n\n\n\n<p class=\"wsu-spacing-after--large\">The USDA list of temperature zones provided in Table 2 is a guide, not a set of absolutes. Personal experience and record-keeping will help you relate this guide to your own garden conditions. An interactive USDA Plant Hardiness Zone map can be found in the Further Reading section of this chapter.<\/p>\n\n\n<span id=\"tablepress-82-description\" class=\"tablepress-table-description tablepress-table-description-id-82\">Table 2. USDA Temperature Zones<\/span>\n\n<table id=\"tablepress-82\" class=\"tablepress tablepress-id-82\" aria-describedby=\"tablepress-82-description\">\n<thead>\n<tr class=\"row-1 odd\">\n\t<th class=\"column-1\">Zone<\/th><th class=\"column-2\">\u00b0Fahrenheit<\/th>\n<\/tr>\n<\/thead>\n<tbody class=\"row-hover\">\n<tr class=\"row-2 even\">\n\t<td class=\"column-1\">1<\/td><td class=\"column-2\">Below \u221250<\/td>\n<\/tr>\n<tr class=\"row-3 odd\">\n\t<td class=\"column-1\">2a<\/td><td class=\"column-2\">\u221250 to \u221245<\/td>\n<\/tr>\n<tr class=\"row-4 even\">\n\t<td class=\"column-1\">2b<\/td><td class=\"column-2\">\u221245 to \u221240<\/td>\n<\/tr>\n<tr class=\"row-5 odd\">\n\t<td class=\"column-1\">3a<\/td><td class=\"column-2\">\u221240 to \u221235<\/td>\n<\/tr>\n<tr class=\"row-6 even\">\n\t<td class=\"column-1\">3b<\/td><td class=\"column-2\">\u221235 to \u221230<\/td>\n<\/tr>\n<tr class=\"row-7 odd\">\n\t<td class=\"column-1\">4a<\/td><td class=\"column-2\">\u221230 to \u221225<\/td>\n<\/tr>\n<tr class=\"row-8 even\">\n\t<td class=\"column-1\">4b<\/td><td class=\"column-2\">\u221225 to \u221220<\/td>\n<\/tr>\n<tr class=\"row-9 odd\">\n\t<td class=\"column-1\">5a<\/td><td class=\"column-2\">\u221220 to \u221215<\/td>\n<\/tr>\n<tr class=\"row-10 even\">\n\t<td class=\"column-1\">5b<\/td><td class=\"column-2\">\u221215 to \u221210<\/td>\n<\/tr>\n<tr class=\"row-11 odd\">\n\t<td class=\"column-1\">6a<\/td><td class=\"column-2\">\u221210 to \u22125<\/td>\n<\/tr>\n<tr class=\"row-12 even\">\n\t<td class=\"column-1\">6b<\/td><td class=\"column-2\">\u22125 to 0<\/td>\n<\/tr>\n<tr class=\"row-13 odd\">\n\t<td class=\"column-1\">7a<\/td><td class=\"column-2\">0 to 5<\/td>\n<\/tr>\n<tr class=\"row-14 even\">\n\t<td class=\"column-1\">7b<\/td><td class=\"column-2\">5 to 10<\/td>\n<\/tr>\n<tr class=\"row-15 odd\">\n\t<td class=\"column-1\">8a<\/td><td class=\"column-2\">10 to 15<\/td>\n<\/tr>\n<tr class=\"row-16 even\">\n\t<td class=\"column-1\">8b<\/td><td class=\"column-2\">15 to 20<\/td>\n<\/tr>\n<tr class=\"row-17 odd\">\n\t<td class=\"column-1\">9a<\/td><td class=\"column-2\">20 to 25<\/td>\n<\/tr>\n<tr class=\"row-18 even\">\n\t<td class=\"column-1\">9b<\/td><td class=\"column-2\">25 to 30<\/td>\n<\/tr>\n<tr class=\"row-19 odd\">\n\t<td class=\"column-1\">10a<\/td><td class=\"column-2\">30 to 35<\/td>\n<\/tr>\n<tr class=\"row-20 even\">\n\t<td class=\"column-1\">10b<\/td><td class=\"column-2\">35 to 40<\/td>\n<\/tr>\n<tr class=\"row-21 odd\">\n\t<td class=\"column-1\">11<\/td><td class=\"column-2\">above 40<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-82 from cache -->\n\n\n\n<p class=\"wsu-spacing-before--large\">Do not confuse USDA hardiness zones with <em>Sunset Magazine\u2019s<\/em> climate zones. In addition to winter lows, these maps take into account the total climate, including length of growing season, timing and amount of rainfall, summer highs, wind, and humidity.<\/p>\n\n\n\n<p>WSU has the largest agricultural weather station network in the country with almost 350 weather stations. AgWeatherNet (AWN) provides Washington farmers and gardeners with weather data to improve crop production. Data may be accessed and retrieved free of charge but an account must be created.<\/p>\n\n\n\n<p>Available rainfall, in all parts of Washington, limits plant growth and results in necessary garden management choices. West of the Cascade Mountains, Seattle averages about 35 inches per year and Olympia about 51 inches. In the east, Spokane receives about 16 inches, and Yakima only 8 inches (information and data from the Western Regional Climate Center, 1971\u20132000). These are averages that cover decades, so rainfall can and does vary year to year. In eastern Washington and mountainous areas of the state, much of the precipitation falls as snow and generally very little during the growing season.<\/p>\n\n\n\n<p>The basic reality for gardeners is that rainfall in all areas of the state falls most heavily from October through February. Rainfall is lightest from March through September when most herbaceous perennials, biennials, and annuals are in active growth. A gardener\u2019s task is to know the region\u2019s water availability realities and plan for sensible water use in the landscape. When selecting plants, consider how the plant will be watered throughout the year. Hardy, spring-blooming bulbs (e.g., <em>Narcissus<\/em>, <em>Tulipa<\/em>) require water during the fall, winter, and spring but are dormant during summer. Their life cycle coincides with the local water patterns throughout the state.<\/p>\n\n\n\n<p>Light levels\u2014both seasonal and daily\u2014also affect plant growth profoundly. Photograph the garden regularly, noting where light strengthens and wanes across the seasons. A series of photographs on the first of January, first of April, first of July, and first of October, showing the garden space from various angles, will be helpful in seeing where sun-loving or shade-requiring plants can thrive. Learning the movement of light across the garden will be as important in choosing plants as studying the soil.<\/p>\n\n\n\n<p>Pictorial records also help as time passes and trees and shrubs grow. Herbaceous perennials may bloom less as they become shaded by taller plants, and a garden\u2019s sunny spots may gradually alter into part-sun or even shade. Perhaps the loss of a large tree or trees may bring shade-loving plants into unwelcome full sun.<\/p>\n\n\n\n<p>Gardens require planning and then revising as time changes them. Fortunately, gardeners enjoy changing the scene by adding and subtracting plants. One particular advantage of plants discussed in this chapter is their ease of handling and transplanting. Their root structures generally do not present the transplanting challenges of established trees and shrubs.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Microclimate<\/em><\/h3>\n\n\n\n<p>Localized landforms and structures can influence the climate of even a very small piece of land so that its growing conditions vary from the surrounding area, creating a microclimate. As you garden, you will notice the difference between a southern slope that thaws readily and a north-facing slope or wall that retains frost. The individual microclimates of any garden will be affected if the garden is near a large body of water (which will moderate both summer and winter temperatures somewhat). Altitude can affect the general climate, but a feature as uncomplicated as a hill can demonstrate different growth patterns at its top and in the low area below it. Cold air flows downhill, pooling in low spots, and may reduce survival of tender plants there. An individual garden\u2019s warming trend may result from nearby pavement, buildings, or rock walls that retain and slowly release heat. Prevailing winds may also require fencing or plantings for windbreaks to protect flowers and vegetable crops.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Winterhardiness<\/em><\/h3>\n\n\n\n<p>A garden\u2019s microclimate is not the only factor affecting a plant\u2019s winter survival. Genetic hardiness is built into the physiology of every plant, and it is for this hardiness that plants are rated for certain zones.<\/p>\n\n\n\n<p>The age of a plant also counts. If it is newly planted and has small roots or if it is weakened by age, chances of survival may be lower. Check on the general health of the roots\u2014they must not be soggy from being overwatered or be sitting in a wet spot in the garden. Finally, soil moisture going into winter makes a difference. Gardeners in zones 3\u20136 should water plants before the first hard freeze. In all zones, gardeners should check plants tucked under building overhangs to be certain they are not dry.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-plant-selection\">Plant Selection<\/h2>\n\n\n\n<p>With thousands of possible choices, it is necessary to focus both on the purpose of the plant and its climate needs.<\/p>\n\n\n\n<p>Choose plants adapted to your zone, then group them in the garden according to water and light needs.<\/p>\n\n\n\n<p>A Japanese-influenced garden design, with conifers and other plants providing shade, might include ferns and mosses. A billowing flower garden in full sun could feature flowers blooming in sequence over several months, with April narcissus, May peonies, late May German iris, June Siberian iris, late June daylilies, and July and August true lilies. The adaptability of herbaceous perennials allows these to tuck against each other, even in a few square feet of space. By choosing for foliage color and texture as well as flowers, your garden design will have multi-season interest.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-maintenance\">Maintenance<\/h2>\n\n\n\n<p>Caring for herbaceous perennials means being sensitive to, and responding to, the rhythm of their growth with the seasons. Observation will tell you that the plants demonstrate what is needed: dead stems in spring with new growth beneath? Trimming is the action needed. Taller plant growth in May, falling sideways? You will know staking is required.<\/p>\n\n\n\n<p>The individual maintenance tasks are not difficult, but if gardeners bring many different genera of plants into the garden, individual action for each plant type will be required throughout the seasons. In early summer, you may be cutting away foliage of dormant poppies (<em>Papaver<\/em> spp.) while tying up delphinium (<em>Delphinium elatum<\/em> and cultivars) that are in their most vigorous growth.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Mulching<\/em><\/h3>\n\n\n\n<p>Like many tasks in gardening, how and when mulching occurs can vary without harming the plants. Some gardeners mulch in both spring and late fall; others apply mulch only once in late fall. The garden will benefit whatever the timing.<\/p>\n\n\n\n<p>As spring growth starts, mulch requires renewing. Research what is available in your area, because mulches differ regionally. Choose mulch with a fine texture, such as composted yard waste, shredded leaves, needles mixed with composted sawdust, or finely chipped tree trimmings.<\/p>\n\n\n\n<p>\u201cFertile\u201d mulch containing some animal manure, such as aged dairy manure mixed with compost, supplies some nutrients to the plants. Choose composted materials rather than fresh manures, which can damage plants and present a health hazard. These finer-textured mulches are pleasant to spread and look \u201cfinished\u201d when tucked around plants. They also break down as the season progresses and add to soil tilth. Their disadvantage is that seeds dropped or blown onto the surface will germinate rapidly. This may be a benefit if you want extra plants from your own perennials or biennials, but it is bothersome when the newly emerging plant proves to be a weed. Coarser mulches reduce, but do not eliminate, weed intrusion.<\/p>\n\n\n\n<p>In the late fall, clip back spent plants and remove dead annuals before applying mulch. This fall cleanup is particularly necessary in the coldest regions where the mulch will provide some protection against winter frost heaving. Gardeners east of the Cascades sometimes use pine needles for winter mulch. Some gardeners in zones 3\u20136 also lay evergreen boughs loosely over perennial plants after the ground freezes.<\/p>\n\n\n\n<p>Always spread mulch over damp ground. If rain has been scarce in either spring or late fall, weed the area and water deeply before mulching.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Watering<\/em><\/h3>\n\n\n\n<p>Many herbaceous perennials require more water during their growing season than our natural rainfall provides anywhere in the state, even our high rainfall areas. Biennials and annuals also need extra irrigation to support small plants in active growth. The more rapidly a plant is growing, and the smaller its roots, the more water, in general, it will require. An annual petunia (<em>Petunia<\/em> \u00d7 <em>hybrida<\/em>) planted from a one-inch start may become a plant three feet wide and two feet tall by the end of the season; this growth cannot occur without water. Seedlings are also vulnerable to drought and can easily be killed if watering is neglected.<\/p>\n\n\n\n<p>When planting, group plants according to their individual water needs. Keeping them watered will be the main task of the summer season. Check reference sources when selecting plants to determine their exact requirements.<\/p>\n\n\n\n<p>Apply enough water to wet plant roots thoroughly, then allow soil to dry an inch or two down. The best way to determine whether plants need water is to probe the root zone with a trowel to gauge moisture. Plants will lose less moisture on overcast days; a calm, cloudy, 70-degree day causes far less water loss than a windy, sunny, 70-degree day. Light rain, even though it may seem to dampen the garden, may fail to reach the plant roots: moisture lands on leaves or mulch but roots stay thirsty. Plants growing under large trees may receive almost no rain.<\/p>\n\n\n\n<p>When adding plants to an established garden, check the soil moisture before planting. Soil often dries between rains. It is helpful to excavate the hole for a new perennial or annual plant, then fill the hole with water and allow it to drain before planting. This supplies moisture at and below the root level\u2014moisture that would be difficult to provide by watering from above. After planting, water thoroughly again. This technique especially gives fall-planted bulbs a good start, because their roots need to emerge into damp soil.<\/p>\n\n\n\n<p>Irrigation systems are installed more easily when plants are still small. Place them early enough in the spring that plants have not covered the soil. Soaker hoses, properly laid out, can make watering chores much easier. They work best if loops of hose are fairly close together, about 12 to 16 inches, and if the hose is pinned to the ground. Placing a light mulch over the installed hose also aids in both attractiveness of the hose and its effectiveness.<\/p>\n\n\n\n<p>If an automatic irrigation system is included in the plans, make sure there is careful positioning of sprinkler or bubbler heads so that no group of plants gets skipped. Deeper, less frequent watering will more likely wet the entire root zone versus frequent, light watering. Frequent contact by water on foliage often increases the incidence of plant diseases.<\/p>\n\n\n\n<p><strong><em>Winter watering<\/em><\/strong>. Some plants, even if rated hardy for their region\u2019s lowest temperatures, may suffer from winterkill if the ground freezes around dry roots. Especially in our coldest regions, gardeners must water plants deeply before freezing occurs. Also, double-check plants under overhangs and eaves which will have sheltered them from rainfall.<\/p>\n\n\n\n<p><strong><em>Waterwise plants<\/em><\/strong>. Some plants can manage with little irrigation once established. \u201cEstablishment\u201d means that the root system of a plant has expanded into the surrounding soil and takes up water efficiently. This process may take up to two years for herbaceous perennials.<\/p>\n\n\n\n<p>If watering occupies too much of your summertime, or to conserve water, add <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#w\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>waterwise<\/strong> (opens in new window)<\/a> plants the next planting season (learn more in Chapter 25: Waterwise Landscaping). Sedums (<em>Sedum<\/em> spp.) and sempervivums, \u201chens and chicks\u201d (<em>Sempervivum tectorum<\/em>), in dozens of fascinating color combinations, tuck in nicely along walkways, in among rocks, and in containers, requiring almost no auxiliary watering. They do need protection from soggy winter soil conditions and should be sited to ensure year-round good drainage. Waterwise and environmentally sensible gardening now extends to <a rel=\"noreferrer noopener\" href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#g\" target=\"_blank\"><strong>green roofs<\/strong> (opens in new window)<\/a> (Figure 1) planted with hardy selections like sedums.<\/p>\n\n\n<div class=\"wp-block-image wsu-spacing-after--large\">\n<figure class=\"alignright size-full\"><img decoding=\"async\" loading=\"lazy\" width=\"600\" height=\"400\" src=\"https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/10\/Fig_1-1.jpg\" alt=\"Fig_1.jpg: A hardscaped path through taller ornamentals leads to a small building with a rooftop garden and lawn chairs also atop. \" class=\"wp-image-2776\" srcset=\"https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/10\/Fig_1-1.jpg 600w, https:\/\/wpcdn.web.wsu.edu\/extension\/uploads\/sites\/62\/2025\/10\/Fig_1-1-300x200.jpg 300w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><figcaption class=\"wp-element-caption\">Figure 1. This rooftop garden is a whimsical addition to the retail building at Living in the Garden, a small garden shop north of Pullman, Washington. (Photo courtesy of Therese Harris.)<\/figcaption><\/figure><\/div>\n\n\n<p>Many perennials have excellent species and cultivars available to enhance the waterwise garden. Look for yarrow (<em>Achillea<\/em> spp.), various artemesias (<em>Artemesia<\/em> \u2018Powis Castle\u2019), coreopsis (<em>Coreopsis verticillata<\/em> \u2018Moonbeam\u2019), coneflower (<em>Echinacea purpurea<\/em> and others), and sun rose (<em>Helianthemum<\/em> sp.). See Chapter 25: Waterwise Landscaping for more information on this topic.<\/p>\n\n\n\n<p><strong><em>Moist or damp conditions<\/em><\/strong>. Some gardeners are fortunate to have a spot that stays damp year-round, or perhaps even a pond. If you are able to provide sufficient water to keep an area thoroughly moist throughout the summer, your plant choices include some beauties. Ferns, astilbes in red, pink, or white (<em>Astilbe<\/em> spp.), filipendula\u2014sometimes called queen of the prairie (<em>Filipendula rubra<\/em>)\u2014lifularia (<em>Ligularia dentata<\/em>), and globe flower (<em>Trollius europaeus<\/em>) will suit moist conditions. If these plants are selected for a place that becomes and stays dry, they will not thrive.<\/p>\n\n\n\n<p><strong><em>Stress from lack of water<\/em><\/strong>. All newly planted herbaceous perennials, even those quite accustomed to dry conditions, such as yarrow, will need water during their first growing season. In addition, regular watering is needed at root depth to help all perennial gardens look their best. Thirsty plants may not expire, but they will grow more slowly and stay smaller. For some plants and some gardeners, slow growth is acceptable. Herb gardens, for instance, can produce more intensely flavorful foliage if plants do not produce well-watered, fast-growing leaves.<\/p>\n\n\n\n<p>Some herbaceous perennials, such as Shasta daisies (<em>Leucanthemum<\/em> \u00d7 <em>superbum<\/em>), are tough and recover well even after leaf wilt. Others, especially the water-lovers like astilbe and ligularia, will show stem as well as leaf wilt with entire parts of the plant drooping to the ground. Bee balm (<em>Monarda didyma<\/em>) has showy flowers that attract bees and hummingbirds but is susceptible to water stress. If any plants wilt in the evening and do not perk up by morning, water is definitely needed. Repeated water stress can kill plants.<\/p>\n\n\n\n<p><strong><em>Stress from too much water<\/em><\/strong>. Certain categories of plants, notably sedums, sempervivums, and woody herbs, will seldom show signs of water stress. They require relatively little water during dry periods\u2014sedums can endure an entire summer gardening season without supplementary water in all but the most arid regions. Winter conditions, especially in western Washington, present these types of plants with another difficulty: soggy roots during winter rains. If planted where drainage is poor, these plants can be killed by drowning, not by freezing, in winter.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Fertilizing<\/em><\/h3>\n\n\n\n<p>If you are starting a completely new garden, a soil test can help determine specific nutrient and pH levels as well as possible needs. If you are working in a previously established garden or adding a few plants at a time to a border, a soil test may be more difficult to implement, but it is better to start with one if possible.<\/p>\n\n\n\n<p>For herbaceous perennials, which store nutrients in roots, rhizomes, or bulbs over the winter, fertilizer in some form is needed when they begin active growth in spring. Some nutrients will be available in the first season if organic components, such as compost, were added when the bed was prepared. A one-inch mulch of fertile material, such as composted dairy manure, can also supply nutrients.<\/p>\n\n\n\n<p>Many gardeners apply a light application of 5\u201310\u201310 in the spring. Several slow-release organic fertilizers are also available and may provide season-long nutrition. Many waterwise plants such as artemesia, sedum, sempervivums, and yarrow become floppy and unattractive if fertilized. As for herbs, if the herb garden grows well and plants have normal color, no fertilizer is needed.<\/p>\n\n\n\n<p><em><strong>Special cases in fertilizing<\/strong><\/em>. Fertilize all spring-blooming bulb clumps (crocus, tulip, narcissus, etc.) when shoots have emerged one to two inches and then once more just after bloom to help with formation of flower embryos for next year. Use a bulb fertilizer with analysis of 9\u20136\u20136, or close to that, following instructions on the package. Water granular fertilizers into the soil using a gentle spray.<\/p>\n\n\n\n<p>A few herbaceous perennials need summer fertilizing. Dahlias (<em>Dahlia<\/em> \u00d7 <em>hybrida<\/em>) and delphiniums (<em>Delphinium<\/em> spp.) are considered heavy feeders and benefit from a low-nitrogen fertilizer at planting time, then a boost six weeks after the first fertilizing, and another six weeks after that. Side-dressing these plants with a 5\u201310\u201310 fertilizer and then watering it in will help their growth. For individual plants, you can also use a liquid fertilizer.<\/p>\n\n\n\n<p>The west side of the state tends to have soils with a pH of 6.5 to 7.5. Gardeners on the west side growing dahlia, dianthus, delphinium, or German iris (<em>Iris germanica<\/em>) will typically need to add lime to adjust the soil pH. Additional lime is rarely needed in eastern Washington.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Grooming and Pruning<\/em><\/h3>\n\n\n\n<p>Seasonal grooming and pruning of herbaceous perennials goes more easily when you understand the way different types grow. Herbaceous perennials with fibrous root systems die to the ground and regrow from a \u201ccrown\u201d just above the roots (e.g., native columbine, <em>Aquilegia formosa<\/em>). During winter, their stems become brittle, stop growing, and do not show a green inner core when broken.<\/p>\n\n\n\n<p>When pruning, remove these old stems, being careful not to chop into any emerging, new stems beneath the dead foliage.<\/p>\n\n\n\n<p>Deadhead your flowers; that is, remove spent flower heads as they finish blooming. Many plants bloom longer and stay more attractive if they are not allowed to go to seed. Removing the first spent flower will result in new side shoots and more bloom on perennials such as campanulas, coreopsis, daylilies, lupine, lavender, and some sages\u2014as well as many others.<\/p>\n\n\n\n<p>Some perennials, when cut back just after bloom, will produce new stems with secondary flowers later in the summer: penstemon (<em>Penstemon<\/em> spp.), foxgloves, and delphinium will offer fresh flowers on new stems. Often the repeat flower is not as tall as the original but is still attractive.<\/p>\n\n\n\n<p>Fall-blooming plants in the composite family, including asters and chrysanthemums, grow sturdier flowers and more compact bushes if merely pinched back. Remove about three inches of growing tips in mid-May and again in early July.<\/p>\n\n\n\n<p>Some spring-blooming perennials disappear in early summer. You will discover foliage dying back on true poppies (<em>Papaver orientale<\/em>) and on native and cultivated bleeding heart (<em>Dicentra formosa, Dicentra spectabilis<\/em>)\u2014these plants simply stop growing and go dormant. Remove the foliage gently when it has completely browned.<\/p>\n\n\n\n<p>At winter\u2019s end, trim back or groom all ornamental grasses. Cut down tall grasses, such as six-foot <em>Calamagrostis<\/em> \u00d7 <em>acutiflora<\/em> and <em>Miscanthus sinensis<\/em>, to about one foot. Huge clumps are better managed if lassoed with rope to hold them together in a pillar shape before cutting below the tied area. Shorter grasses can be taken down to about four or five inches before spring growth begins.<\/p>\n\n\n\n<p>Some plants set attractive seedpods. Species peonies, many poppies, and Siberian iris (<em>Iris sibirica<\/em>) produce intriguing stalks of seedpods that dry well and can add to winter garden interest or dried flower arrangements. Prune out these old stalks before spring growth begins.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Staking<\/em><\/h3>\n\n\n\n<p>Staking or support is needed for plants that grow tall, like the larger lilies (<em>Lilium<\/em> spp.), or grow weak stems (<em>Ligularia<\/em> spp.), or have top-heavy, multi-petal flowers that might fall in rain, as with peonies or dahlias. Dahlias and delphiniums have hollow stems; once broken, they cannot be re-staked. Other plants, such as compact, hardy geraniums (<em>Geranium macrorrhizum<\/em> and many others), may never require staking. If your garden is windy, you will need to stake susceptible plants. In addition, you can look for shorter, tougher cultivars of plants: Asiatic lilies grow shorter (2\u20134 feet) than Oriental lilies (6\u20138 feet) when established, so Asiatic lilies are wise choices for windy gardens.<\/p>\n\n\n\n<p>Use single uprights for plants with single stems. Bamboo poles, slender wood poles, metal poles, or plastic stakes work. The stake should be about three-quarters the height of the plant\u2019s final size. Tie the plant stem as it grows using flexible plastic or cloth ties. In some cases, you may wish to set the stake when planting, as is often done with dahlia tubers. With large lilies, you also place the stake when planting to avoid later piercing the vulnerable bulb.<\/p>\n\n\n\n<p>Bushy or floppy plants require either twiggy brush placed to hold up the plant or short stakes surrounding it. Three or four short stakes with crisscrossed string will work well for this purpose. Commercial wire hoops and supports are also good choices, especially for heavy plants like peonies.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-common-problems\">Common Problems<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Powdery Mildew<\/em><\/h3>\n\n\n\n<p>This fungal disease results in an obvious layer of gray, disfiguring spores on a plant. Sometimes, it appears as spots, but often it covers an entire leaf, giving it a \u201cfuzzy\u201d appearance. Many species of powdery mildew are present in Washington, some of which affect only one plant while other species have a wide range of hosts.<\/p>\n\n\n\n<p>Common where summer produces warm days and cooler nights, powdery mildew is present in nearly all gardens somewhere during the season. This disease can cause leaf drop, deformation, or simply reduce the leaf\u2019s efficiency at photosynthesis.<\/p>\n\n\n\n<p>Powdery mildew is common on roses, zinnias, dahlias, pansies, begonias, squash, and many other plants.<\/p>\n\n\n\n<p><a href=\"https:\/\/hortsense.cahnrs.wsu.edu\/\" data-type=\"URL\" data-id=\"https:\/\/hortsense.cahnrs.wsu.edu\/\" target=\"_blank\" rel=\"noreferrer noopener\">Hortsense (opens in new window)<\/a>, the WSU guide to plant problems and their control, has photographs of common powdery mildew. Be sure to check Hortsense for its recommendations on plant problem management for each plant problem you encounter.<\/p>\n\n\n\n<p>Planting in a sunny spot with good air circulation helps reduce powdery mildew. Even plants that are seldom bothered by powdery mildew can be affected if they are planted too closely and crowded against other plants.<\/p>\n\n\n\n<p>Prune out affected leaves. Some growers, particularly those confronted with a powdery mildew infection that covers the entire plant, as may be the case with dahlias late in the season, allow the plant to end its growth naturally and then discard the entire top growth after frost. Do not add the mildewed leaves to compost piles. Review Hortsense for other management tips.<\/p>\n\n\n\n<p>Some plants show resistance to powdery mildew, such as the \u2018Jacob Cline\u2019 bee balm (<em>Monarda didyma<\/em>). Resistance is not equivalent to immunity. The plant may develop fewer symptoms but it can still be affected.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Aphids<\/em><\/h3>\n\n\n\n<p>Many different species of aphid are present in Washington gardens. They hatch in the spring just as plant growth begins. Once active leaf formation starts, aphids are vigorous and hungry. As their leaves mature, plants can endure a certain amount of aphid activity but the insects can be damaging on the youngest leaves, causing curling and reducing photosynthesis. Because they reproduce prolifically, aphids can cover an entire plant.<\/p>\n\n\n\n<p>Wash them off with a gentle stream of water, encourage beneficial insects, and use mild insecticidal soap for the worst infestations. Check Hortsense for specific current recommendation. Avoid insecticides that harm ladybugs, lacewings, and other beneficial predators that will eat aphids. Many birds, including hummingbirds, also eat aphids.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Slugs and Snails<\/em><\/h3>\n\n\n\n<p>Gardeners sometimes cope with their slug invasions by joking that the imported European garden slugs may qualify as the most discussed and disgusting of garden pests. Slugs and snails, both classified as mollusks, can rapidly damage plants, especially those with new, tender growth. Two common types in Washington are the European black garden slug (<em>Arion ater<\/em>) and the great gray garden slug (<em>Limax maximus<\/em>). Note that some native slugs, such as the banana slug (<em>Ariolimax columbianus<\/em>), are valuable recyclers in forests, especially in western Washington, and should be protected. The imported garden slugs also recycle plant materials, but they unfortunately do not always wait for the material to die before munching it.<\/p>\n\n\n\n<p>Plants favored by slugs and snails include many favorite garden choices: delphinium, iris, pulmonaria, dahlia, brunnera, hosta, iris, all lilies, spring-blooming narcissus, and tulips. Vegetable starts can be decimated just as they germinate, or they can be chomped when they have a few true leaves. Damage may be most serious in late spring when weather is moist and cool and plants begin their growth. Slugs, however, stay active throughout the growing season.<\/p>\n\n\n\n<p>Slugs and snails reproduce by eggs. Look for small patches of translucent or pearly eggs, less than one-quarter inch in diameter, in clumps of a few to more than 50. They will be tucked into mulch, under the edges of rotting wood, or even down in the soil. You will probably find them by accident more often than by hunting.<\/p>\n\n\n\n<p>Scoop them out with a trowel, drop them on a piece of newspaper, and crush them. Slug eggs may be visible throughout the year, but the heaviest mating periods are in August and September.<\/p>\n\n\n\n<p>If you have planted handsome perennial ground covers, they offer great hiding places for slugs. Trim foliage so it clears the ground a bit, and avoid laying fresh mulch until plants finish their spring growth and just the top of the soil dries a bit.<\/p>\n\n\n\n<p>Handpicking\u2014or glove-picking if you prefer\u2014reduces the population somewhat when done regularly. If your plants hang down over brick or rock walls, lift the dangling foliage to find more slug hiding spots. Also, try placing a wet board or wet newspaper on the ground and checking under it in early evening or morning for slug invaders. Lift or tip container plants to check, because slugs hide underneath pots, even those placed up on decks and patios. Vigilance and patience helps, because no single system will manage slugs.<\/p>\n\n\n\n<p>Check with Hortsense for current chemical control recommendations. Use the least toxic control available.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Weeds<\/em><\/h3>\n\n\n\n<p>As with herbaceous garden plants, weeds are also categorized as annuals, biennials, and perennials. Although annual and biennial weeds can be a nuisance, perennial weeds can be very difficult to deal with. Common perennial weeds include field horsetail, quackgrass, hedge bindweed (common morningglory), field bindweed, and Canada thistle. These weeds are very invasive, because once established, they spread rapidly by roots or rhizomes as well as by seed.<\/p>\n\n\n\n<p>When establishing a perennial bed, try to control all perennial weeds. This may require extensive digging with careful removal of all roots and rhizomes. Where roots are too deep, an herbicide may be effective in controlling the weed. Before attempting any weed control, proper identification is important so a targeted control strategy can be implemented.<\/p>\n\n\n\n<p>Removing perennial weeds from an established perennial garden is even more difficult. In many cases, the weed may be growing within the root ball of the desirable perennial. Removal of the weed will be impossible without digging up the garden perennial during the dormant season, removing the weed roots or rhizomes, and resetting the plant. Although herbicides may be available for removing a grass weed from a broadleaf herbaceous perennial, an herbicide may not be available to remove grass weeds from a perennial grass planting nor broadleaf weeds from broadleaf herbaceous perennials.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-specific-garden-styles\">Specific Garden Styles<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Container Gardens<\/em><\/h3>\n\n\n\n<p>Growing plants for portability has a long history, as gardeners have long appreciated the convenience and practicality of putting plants into pots. Pots may be nearly any size and any material\u2014 including old sneakers, kitchen colanders, and perforated teacups, to name a few. The one firm, definite requirement is that the container, no matter its type, must drain well. Plants left sopping without drainage will rapidly succumb to rot, unless they are among the relatively few adapted to wet conditions. If the container lacks drainage holes, add holes or use another container.<\/p>\n\n\n\n<p>Choose a potting soil that has gritty texture, with perlite or pumice incorporated for drainage, to maintain soil structure and improve nutrient holding capacity. Some gardeners use basic commercial potting soils but add one-quarter pumice by volume and a few scoops of screened compost.<\/p>\n\n\n\n<p>When potting, cover the drainage holes with a simple piece of screen, a bit of broken crockery, a piece of wallboard tape, or even a coffee filter. You want the water to drain well but not to carry the potting mix with it. Do not add gravel, rocks, piles of pottery, or any other lower layer to the pot. Fill it completely with thoroughly dampened potting soil. Settle the plants in the potting mix and water well.<\/p>\n\n\n\n<p>Annuals, especially those planted from seed or from small one-inch starts, require time; annuals started at one-inch fill out in six to seven weeks. Keep soil evenly moist for annuals and vegetables. Hanging baskets and pots that receive afternoon sun during elevated temperatures will need a daily watering, or even more frequently as needed. Hanging baskets require particular care; if they dry out, take them down and immerse the entire basket in water to rewet the dried-out soil. Most hanging baskets purchased for the home become increasingly difficult to remain productive. By late summer the root growth will take over much of the soil volume in the container.<\/p>\n\n\n\n<p>Fertilize container plantings every two weeks with a liquid fertilizer. Choose one with trace elements and a fairly low nitrogen level, such as a 5\u201310\u201310. Excess nitrogen in container plantings will result in foliage rather than blooms. Some gardeners prefer to use half strength fertilizer weekly. Do not fertilize a dry pot as the water and nutrients may drain quickly through the soil. Water thoroughly one day and fertilize the next.<\/p>\n\n\n\n<p>Deadhead all container plants to encourage continuous bloom or food production.<\/p>\n\n\n\n<p class=\"wsu-spacing-after--xsmall\">Some annuals, such as sweet alyssum, lobelia, begonia, and coleus, can be started from seed and do well in containers. The list below shows some recommended annuals for containers that are harder to start from seed, thus are vegetatively propagated.<\/p>\n\n\n\n<ul class=\" wsu-list--columns-2\">\n<li><em>Bacopa<\/em><\/li>\n\n\n\n<li><em>Bidens<\/em><\/li>\n\n\n\n<li><em>Calibrachoa<\/em> hybrids (million bells)<\/li>\n\n\n\n<li><em>Diascia<\/em><\/li>\n\n\n\n<li><em>Nemesia<\/em><\/li>\n\n\n\n<li><em>Osteospermum<\/em> hybrids<\/li>\n\n\n\n<li><em>Petunia<\/em> hybrids<\/li>\n\n\n\n<li><em>Scaevola<\/em> (fan \ufb02ower)<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading wsu-spacing-before--xxmedium\"><em>Herb Gardens<\/em><\/h3>\n\n\n\n<p>For centuries, gardeners have cherished plants for their culinary and medicinal properties. Herb gardens may be elaborately formal or planted in circular or maze patterns, but simple beds of herb plants provide kitchen supplies just as readily. Even the smallest landscape has room for a few edible herbs\u2014many just require full sun and only moderate water.<\/p>\n\n\n\n<p>Thyme (<em>Thymus<\/em> spp.), chives (<em>Allium schoenoprasum<\/em>), and oregano (<em>Origanum vulgare<\/em>) will survive zone 5 winters. Peppermints (<em>Mentha<\/em> sp.) can be so invasive that confining them to a deep pot makes sense. Cat lovers can grow true catnip, <em>Nepeta cataria<\/em>, which has handsome blue flowers that may not be obvious when draped with a cat.<\/p>\n\n\n\n<p>Some familiar herbs are <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#s\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>sub-shrubs<\/strong> (opens in new window)<\/a>, meaning they have a woody structure that persists, including lavender and rosemary. These often retain leaves through winter in zones 7\u20139, although many are too tender for zones 4\u20136. Common English lavender (<em>Lavandula angustifolia<\/em>) will, however, survive zone 5 winter temperatures, although it may look battered by spring. Sub-shrubs do not recover if they are chopped to the ground or if the branches are cut back too deeply. Trim them gently after bloom or in earliest spring in colder areas, removing about one-third of the growth.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Cutting Gardens<\/em><\/h3>\n\n\n\n<p class=\"wsu-spacing-after--xsmall\">Choosing plants to harvest for bouquets engages many gardeners; the combination of shrubs and smaller plants can yield texture and nearly year-round flowers or foliage. The list below shows some of the common annuals grown for flower bouquets.<\/p>\n\n\n\n<ul class=\" wsu-list--columns-4\">\n<li>Annual phlox<\/li>\n\n\n\n<li>Blanket flower<\/li>\n\n\n\n<li>Celosia<\/li>\n\n\n\n<li>China aster<\/li>\n\n\n\n<li>China pink<\/li>\n\n\n\n<li>Cornflower<\/li>\n\n\n\n<li>Cosmos<\/li>\n\n\n\n<li>Dahlia<\/li>\n\n\n\n<li>Globe amaranth<\/li>\n\n\n\n<li>Heliotrope<\/li>\n\n\n\n<li>Larkspur<\/li>\n\n\n\n<li>Lisianthus<\/li>\n\n\n\n<li>Love-in-a-mist<\/li>\n\n\n\n<li>Lupine<\/li>\n\n\n\n<li>Marigold<\/li>\n\n\n\n<li>Painted tongue<\/li>\n\n\n\n<li>Pot marigold<\/li>\n\n\n\n<li>Salvia<\/li>\n\n\n\n<li>Snapdragon<\/li>\n\n\n\n<li>Spider flower<\/li>\n\n\n\n<li>Statice<\/li>\n\n\n\n<li>Strawflower<\/li>\n\n\n\n<li>Stock<\/li>\n\n\n\n<li>Sunflower<\/li>\n\n\n\n<li>Sweet pea<\/li>\n\n\n\n<li>Sweet William<\/li>\n\n\n\n<li>Verbena<\/li>\n\n\n\n<li>Zinnia<\/li>\n<\/ul>\n\n\n\n<p>For gifts or for sharing at community events, home-grown bouquets reward gardening efforts. Donations of food to community food banks can include flowers as cheerful extras.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Butterfly Gardens<\/em><\/h3>\n\n\n\n<p class=\"wsu-spacing-after--xsmall\">Flowers can attract not only butterflies but many beneficial insects. In general, the greater the variety of genera of plants grown, the more assistance the garden gives to beneficial insects. Flowers with umbel-shaped blooms, such as angelica, fennel, dill, and yarrow, can feed many types of insects. See the partial list of annuals that help attract beneficial insects.<\/p>\n\n\n\n<ul class=\" wsu-list--columns-2\">\n<li>Blanket flower<\/li>\n\n\n\n<li>Four o\u2019clock<\/li>\n\n\n\n<li>Globe amaranth<\/li>\n\n\n\n<li>Heliotrope<\/li>\n\n\n\n<li>Mexican sunflower<\/li>\n\n\n\n<li>Petunia<\/li>\n\n\n\n<li>Scarlet sage<\/li>\n\n\n\n<li>Spider flower<\/li>\n\n\n\n<li>Verbena<\/li>\n<\/ul>\n\n\n\n<p>A water source also helps insects during drier months. Even wasps and bees will sip at the edges of birdbaths, while many butterflies prefer muddy spots.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Bird-Friendly Gardens<\/em><\/h3>\n\n\n\n<p>Water, even in a small container\u2014no tumbling waterfalls needed\u2014and a variety of plants can help attract and sustain birds year-round. Check with your local <a href=\"https:\/\/www.audubon.org\/about\/audubon-near-you?state=WA\" data-type=\"URL\" data-id=\"https:\/\/www.audubon.org\/about\/audubon-near-you?state=WA\" target=\"_blank\" rel=\"noreferrer noopener\">Audubon chapter (opens in new window)<\/a> to determine which plants best serve the birds in your particular region.<\/p>\n\n\n\n<p>In general, scarlet runner bean (<em>Phaseolus coccineus<\/em>) brings hummingbirds during the summer, while sunflowers, cosmos, and zinnias encourage the American goldfinch, Washington\u2019s state bird. Chickadees feed on sunflower and dahlia seeds in autumnal gardens. Many different birds will visit a varied garden.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Native Plant Gardens<\/em><\/h3>\n\n\n\n<p>Native plants suit many different types of landscaping, such as prairie restoration, where appropriate. Streamside plantings can help retain banks and prevent erosion. Incorporating native plants, such as the familiar trillium (<em>Trillium ovatum<\/em>), into your own landscape can help build native plant populations and teach people about threatened or scarce plants. Shrubby native currant (<em>Ribes sanguineum<\/em>) is often added to landscapes for spring bird feeding as well as for its beauty.<\/p>\n\n\n\n<p>If given extra water and fertilizer, native plants will grow larger than they do in their undisturbed habitat. Altering their desired conditions may not be ideal. For example, fertilizing native plants will sometimes result in soft, unhealthy growth. After the first two years of adaptation, reduce watering to allow native plants to respond to normal summer water conditions.<\/p>\n\n\n\n<p>Some gardeners assume that native plants guarantee a low-water use garden; keep in mind that native plants differ as much in their needs as do introduced plants.<\/p>\n\n\n\n<p>Grouping native plants according to their water needs is vital: salal (<em>Gaultheria shallon<\/em>), ground cover mahonia (<em>Mahonia nervosa<\/em>), and sword fern (<em>Polystichum munitum<\/em>) require similar conditions. Learn the exact requirements of native plants\u2014some thrive in moist conditions, such as western tiger lily (<em>Lilium occidentale<\/em>) and red columbine (<em>Aquilegia formosa<\/em>).<\/p>\n\n\n\n<p>In conjunction with conservation groups, gardeners may be able to salvage plants in the path of land clearing. Check local garden centers, local chapters of the Washington Native Plant Society, or with your conservation district for sources of native plants. Many counties have spring sales of native plants. Do not remove plants from \u201cnatural\u201d areas without proper permission.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Edible Landscape Gardens<\/em><\/h3>\n\n\n\n<p>Consider using fruit and vegetable plants throughout the landscape where appropriate. Alpine strawberries (<em>Fragaria vesca<\/em>) make good garden edging in sunny spots. Artichokes (<em>Cynara<\/em> spp., zones 7\u20138) offer striking leafy punctuation as well as a food source. Investigate choices and look into new resources on the \u201cmunchable\u201d garden as it becomes one of the primary interests of the 21st century gardener.<\/p>\n\n\n\n<p>If using flowers for garnish or for edible petals, be certain the chosen plant is not toxic, and if in doubt, <em>Do Not Eat It!<\/em> Some of the many common but toxic plants include daffodils (<em>Narcissus<\/em> spp. and cultivars), monkshood (<em>Aconitum napellus<\/em>), and foxglove (<em>Digitalis<\/em> spp.). Reliably edible flowers include calendulas, daylilies, nasturtiums, pansies, roses, and violas, but even these may present problems for people with allergies. Never eat any plant from a yard where dogs and cats are allowed to roam free. If you have applied any kind of pesticide (any insecticide, herbicide, fungicide, etc.) to a plant, do not eat any part of that plant unless the pesticide label allows use on that specific plant and gives directions on how long you must wait between application and harvest. Be sure and follow all label directions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-specific-garden-plants\">Specific Garden Plants<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Spring-Blooming Hardy Bulbs<\/em><\/h3>\n\n\n\n<p>Spring\u2019s arrival coincides with the emergence of hardy bulbs and corms that come up while temperatures are still cool. The pleasure of seeing daffodils (<em>Narcissus<\/em> spp.), crocus (<em>Crocus<\/em> spp.), and tulips (<em>Tulipa<\/em> spp.) starts the garden year.<\/p>\n\n\n\n<p>These hardy plants have specific timing requirements. They must be planted in the fall, from September in the coldest zones through November in zones 7\u20138, after soil cools, and before hard freezing occurs. Their growth begins at planting; during the winter their roots grow slowly. Most need 11 to 14 weeks of cold temperatures (below 45\u00b0F) to prepare them for flowering. Choose a sunny spot with good drainage for best performance.<\/p>\n\n\n\n<p>Gardeners commonly find unplanted hardy bulbs in bags or boxes, forgotten, as late as February; these can be planted but they will have small or absent blooms. Narcissus can recover and may bloom the next year; tulips seldom do.<\/p>\n\n\n\n<p>Fertilize bulbs when planting and again in spring when plants are about two inches tall. Use a granular 5\u201310\u201310 fertilizer, watered in well, or a bulb fertilizer (about 9\u20136\u20136). Many organic fertilizers are available but spring applications to cold, wet soils will not always provide readily available nutrients to the plants.<\/p>\n\n\n\n<p>When blooming finishes, allow foliage to die back without interference. Snowdrops (<em>Galanthus nivalis<\/em>), crocuses, hyacinths, and tulips need thoroughly brown leaves, indicating that the bulb has received as many nutrients as possible from the leaves. All daffodils may be cut back six to seven weeks after bloom finishes, even if the leaves remain slightly green. Spring-blooming hardy bulbs are fully dormant during the summer months, returning to root growth in September and October with fall rains.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Lilies, True Lilies, and Daylilies<\/em><\/h3>\n\n\n\n<p>Many plants have \u201clily\u201d in the common name, but the true lilies are bulbs in the genus <em>Lilium<\/em>. They add color to summer gardens and return reliably season after season when they are well- established. True lilies include Asiatics, Orientals, Trumpets, and Oriental-Trumpet hybrids.<\/p>\n\n\n\n<p>True lilies have bulbs, like tulips and alliums, but their bulbs do not have a permanent protective coat. The botanical term for this is <a rel=\"noreferrer noopener\" href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#i\" target=\"_blank\"><strong>imbricate<\/strong> (opens in new window)<\/a>, whereas bulbs like tulips are <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#t\" data-type=\"URL\" data-id=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#t\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>tunicate<\/strong> (opens in new window)<\/a>; that is, they have an outer layer, or tunic. Because true lilies lack this protection, and because they seldom go fully dormant, you will find them packed with a layer of sawdust, wood shavings, or other protection when shipped. Plant lilies as soon as you receive them and take care to avoid bruising the unprotected outer scales.<\/p>\n\n\n\n<p>Good drainage means good lily growing; they require regular water during active growth, but they cannot endure soggy ground conditions. If your garden is primarily clay soil, your lilies will grow best in containers or prepared raised beds.<\/p>\n\n\n\n<p>After bloom, remove as little of the stem as possible in order to \u201cfeed\u201d the bulb; just cut off the spent flower then allow the rest of the stalk to go completely brown before trimming it back.<\/p>\n\n\n\n<p>Lily species vary in their needs. Some, such as the Oregon native <em>Lilium pardalinum<\/em>, require ample moisture throughout the growing season. Be sure you check the specific planting needs when selecting.<\/p>\n\n\n\n<p>Daylilies, often confused with true lilies (<em>Lilium<\/em> spp.), are actually in the genus <em>Hemerocallis<\/em>. These valuable landscape plants flower beginning midsummer for about six weeks. They open flowers one at a time, with today\u2019s flowers withered by tomorrow, thus their \u201cdaylily\u201d name. Their toughness can be seen in older plantings of the common lemon-colored <em>Hemerocallis flava<\/em>, which has been grown since the sixteenth century and carries on well even in neglected spots. But modern hybrid daylilies (<em>Hemerocallis<\/em>, \u2018Mary Todd,\u2019 for example) bloom best when they receive supplementary summer water.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Peonies<\/em><\/h3>\n\n\n\n<p>With glorious flowers worth waiting for, herbaceous peonies (<em>Paeonia lactiflora<\/em> and hybrids) have been grown for centuries in landscape gardens. These lush plants can grow for decades without disturbance, and once they settle in and begin to bloom, they are best left alone.<\/p>\n\n\n\n<p>Peony growth stalls when they are newly planted or transplanted. Choose a sunny site but check the pH of the soil, because peonies grow best at a pH of 6.0\u20137.0. They can, however, endure a range both toward acid and toward alkaline. They do particularly well east of the mountains in Washington, because they require significant winter chill for best bloom. Fertilize in early spring with a 5\u201310\u201310 or equivalent.<\/p>\n\n\n\n<p>If peonies fail to bloom but produce healthy leaves, they may just be too young. Herbaceous peonies take at least two to three years to settle into bloom after planting. But check the depth of the planting: if the \u201ceye,\u201d or growing point, which is roughly pointed and pinkish white, is planted deeper than one to two inches, the plant will look fine but will not bud. If the peony is planted too deep, dig it and reset it when its leaves drop in the fall.<\/p>\n\n\n\n<p>Peony hybridizers have, during the last 40 years, developed <a href=\"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/glossary\/#i\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>intersectional peonies<\/strong> (opens in new window)<\/a> resulting from crosses between the herbaceous <em>P. lactiflora<\/em> and the woody tree peony <em>P. lutea<\/em> (other crosses have also been made). These peonies, called Itoh in honor of their first breeder, Toichi Itoh, offer vigorous blooms that open over several weeks. They are robust, and some evidence exists that they can bloom without as much winter chill as others. Initial cultivars were yellow tones but they are now available in most peony tones, white through red. Look for future additions in this newer category of garden peonies.<\/p>\n\n\n\n<p>Sometimes as peonies develop their large flower buds, ants wander onto the plants. People sometimes say, \u201cThe ants make the peonies bloom,\u201d but the ants have just arrived for food in the form of a sticky, sweet residue on the buds. When picking peonies for bouquets, swish the flowers in a bucket of water to remove ants. The ants do not harm the peonies but they alarm dinner guests.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><em>Ground Cover Plants<\/em><\/h3>\n\n\n\n<p>Practical necessity governs the planting of ground covers, a rather dull term for what can be elegant, hard-working, and invaluable plants. Their mission in the landscape can be (1) as slope-holding erosion preventers, (2) as lawn replacements where lawns fail to thrive, (3) for creating a lower layer of uniform texture if planted in large quantities, or (4) for adding texture and interest to paving or shrub and tree plantings. A ground cover can also be a \u201cmass planting\u201d used for landscape effect.<\/p>\n\n\n\n<p>In general, ground covers top out at about 18 inches in height. As with everything in gardening, there are exceptions. When a ground cover is created using small shrubs, such as bearberry cotoneaster (<em>Cotoneaster dammeri<\/em>), a planting may grow to two feet. Some valuable choices, often planted between stones or in pathways, might be only three to six inches tall when fully mature. Some thyme (<em>Thymus<\/em> spp.) cultivars fill in when given good drainage and sun but sometimes only stand two inches tall. The balance and design of the landscape will dictate height of the acceptable ground cover. On larger landscapes, a taller ground cover may be aesthetically pleasing. Generally, plants of approximately the same height are chosen to cover one area.<\/p>\n\n\n\n<p>Consider the look and functionality of the landscape when choosing ground covers. Some landscapes may benefit from evergreen ground covers, and some will benefit from winter-dormant ground covers. The garden will also result from overall choices about how the landscape is to look and function year-round. Two tidy, classic choices are Japanese spurge (<em>Pachysandra terminalis<\/em>) and bunchberry (<em>Cornus canadensis<\/em>), both suited to plantings in acidic soils and shady areas under trees and shrubs. Kinnikinnick and woolly thyme can tolerate alkaline soils and sunny sites.<\/p>\n\n\n\n<p>Match the ground cover to your specific garden conditions. A sunny slope may be ideal for creeping juniper (<em>Juniperus horizontalis<\/em> and its cultivars). They are often drought-tolerant once established but cannot be left alone to sprawl for decades without attention. When they become crowded, junipers are susceptible to disease problems and can develop dead areas in their centers, so, like all garden plants, they must be properly maintained.<\/p>\n\n\n\n<p>Ground covers may also control or minimize weed infestations, though this effect does not occur when the plants are newly installed and have not spread thoroughly. A frequently used ground cover in Washington, the native kinnikinnick (<em>Arctostaphylos uva-ursi<\/em>), develops excellent weed resistance after two to three years of care. When first planted, though, it has many open spaces between branches, providing good shelter for weeds and weed seeds. Maintenance for all newly planted ground covers is often focused on weeding for the first few years until the soil is fully shaded by the desired plants.<\/p>\n\n\n\n<p>Avoid \u201cthuggish\u201d or invasive plants as you choose ground covers. While it may be helpful to have a plant that covers territory with speed, this trait can be a sign of future difficulties. Spotted deadnettle (<em>Lamium maculatum<\/em>) roots wherever a stem touches soil; in some gardens it is manageable, in others, a complete pest. The individual garden conditions affect plant vigor. Another one that can be tricky to manage is sweet woodruff (<em>Galium odoratum<\/em>), a determined spreader. Check with experts and nurseries in your area to determine which plants have colonized local gardens too enthusiastically. Most important, review the noxious weed list for your particular county; several cultivars of English ivy (<em>Hedera helix<\/em>) are listed as noxious weeds in Washington. English ivy can rapidly take over a perennial garden, and it can also climb and damage trees. In addition, it provides cover for rodents, especially rats. In spite of this, recommendations for using it persist.<\/p>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-learning-more\">Learning More<\/h2>\n\n\n\n<p>The best approach to gardening is doing it, but there is a lot of value in reading catalogs, attending classes on perennials, or checking the newest information online from reliable sources. This will help pass the winter months much quicker. Plant breeders are continually working to develop and introduce new cultivars to the gardening world. Plant hunters worldwide still gather seeds from exotic plants and test in local trials. Check seed catalogs and local nurseries regularly for plants that might work in your garden. The best results will come from your own study and experience working in your specific garden conditions.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h2 class=\"wp-block-heading  wsu-heading--style-marked\" id=\"ch11-further-reading\">Further Reading<\/h2>\n\n\n\n<p>Brickell, C., and J.D. Zuk, eds. 2004. <em>The American Horticultural Society A to Z Encyclopedia of Garden Plants<\/em>, revised edition. DK Publishing.<\/p>\n\n\n\n<p>Burnie, G. 2001. <em>Encyclopedia of Annuals and Perennials<\/em>. Fog City Press.<\/p>\n\n\n\n<p>Fitzgerald, T. 2001. Landscaping with Native Plants in the Inland Northwest. <em>Washington State University Extension Publication<\/em> MISC0267. Washington State University.<\/p>\n\n\n\n<p>Fitzgerald, T., S. McCrea, D. Notske, M. Burtt, J. Flott, and M. Terrell. Landscape Plants for the Inland Northwest. <em>Washington State University Extension Publication<\/em> EB 1579. Washington State University.<\/p>\n\n\n\n<p>Leigh, M. 1999. Grow Your Own Native Landscape: A Guide to Identifying, Propagating, and Landscaping with Western Washington Native Plants. <em>Washington State University Extension Publication<\/em> MISC0273. Washington State University.<\/p>\n\n\n\n<p>Lovejoy, A., and L.H. Openshaw. 1999. <em>Ortho\u2019s All About Annuals<\/em>. Meredith Books.<\/p>\n\n\n\n<p>Mackin, J. 1993. <em>The Cornell Book of Herbs and Edible Flowers<\/em>. Cornell Cooperative Extension.<\/p>\n\n\n\n<p>McMoran, D. 2015. How to Determine Your Garden Microclimate. <em>Washington State University Extension Publication<\/em> FS181E. Washington State University.<\/p>\n\n\n\n<p>Perennials for the Inland Northwest, Volume 1: Selecting Plants and Cultural Practices. <em>Washington State University Extension Publication<\/em> MISC0254. Washington State University.<\/p>\n\n\n\n<p>Perennials for the Inland Northwest, Volume 2: Special Uses, Favorite Perennials, and Varieties. <em>Washington State University Extension Publication<\/em> MISC0255. Washington State University.<\/p>\n\n\n\n<p>USDA Agricultural Research Service. n.d. <a href=\"https:\/\/planthardiness.ars.usda.gov\/\" target=\"_blank\" rel=\"noreferrer noopener\">Plant Hardiness Zone Map (opens in new window)<\/a>.<\/p>\n\n\n\n<p>WSU AgWeatherNet. <a href=\"https:\/\/weather.wsu.edu\/\" target=\"_blank\" rel=\"noreferrer noopener\">Summary Reports: Current Conditions (opens in new window)<\/a>.<\/p>\n\n\n\n<p><a href=\"https:\/\/pubs.extension.wsu.edu\/\" data-type=\"URL\" data-id=\"https:\/\/pubs.extension.wsu.edu\/\" target=\"_blank\" rel=\"noreferrer noopener\">WSU Extension Publications Store (opens in new window)<\/a>. 2023. Washington State University.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Jim Kropf, Pierce County Extension Director, Agricultural and Natural Resources Unit, Washington State University Herbaceous Plants in the Landscape Trends and styles in gardening may vary from year to year, but the basic delight gardeners find in the details and presence of plants remains constant. The term \u201cornamental gardening\u201d now seems outdated; plants are often [&hellip;]<\/p>\n","protected":false},"author":241,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_wsuwp_accessibility_report":null},"categories":[],"tags":[],"_links":{"self":[{"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/pages\/1282"}],"collection":[{"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/users\/241"}],"replies":[{"embeddable":true,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/comments?post=1282"}],"version-history":[{"count":28,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/pages\/1282\/revisions"}],"predecessor-version":[{"id":4640,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/pages\/1282\/revisions\/4640"}],"wp:attachment":[{"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/media?parent=1282"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/categories?post=1282"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/extension.wsu.edu\/pnw-gardeners-handbook\/wp-json\/wp\/v2\/tags?post=1282"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}