TREES & SHRUBS
Serviceberry – Amelanchier alnifolia
Multi-stemmed shrub or small tree; 10-12 ft tall, 20 feet wide
Small white flowers, blueberrylike berries, fall color
Low water, but may require watering during dry spells
Suckers readily
Blue Mist Spirea – Caryopteris x clandonensis
Late summer blue color; attracts butterflies and bees
2-3 ft tall, 3 ft wide; deciduous
Requires occasional deep soaking, but is generally adaptable to dry conditions
Catalpa species
Moderate to fast growing to 40-70 ft, 20-40 ft wide
Well adapted to extremes of heat and cold; leafs out late in spring
Low to moderate water; benefits from deep watering during prolonged drought
Large, white flowers early summer, bean-shaped seed capsules – somewhat messy
Hackberry – Celtis occidentalis
Broad, oval shape to 50-60 ft., spread to 40-50 ft., small orange-red fruit
Once established needs little supplemental water
Prone to Hackberry nipplegall on leaves but does no harm to tree
Green Ash – Fraxinus pennsylvanica (seedless male clones best)
50-60 ft. tall, 30-40 ft. wide
Tolerates moist to dry conditions – slower growing in dry conditions
Susceptible to leaf curl, ash aphid, scale; susceptible to borers if drought stressed
Juniperus species
Evergreen foliage, small berry-like cones
Little to moderate water; well-drained soil
Beauty Bush – Kolkwitzia amabilis
Deciduous shrub 6-10 ft., spreads 4-8 ft.; finely branched, multiple upright stems, early summer flowers
Gray-green leaves to 3 in. long sometimes turn reddish in fall
Moderate drought tolerance, best with occasional deep soaking
Golden Raintree – Koelreuteria paniculata
Smaller accent tree to 20-30 ft., spread 25-35 ft.
Midsummer flowers, lantern-shaped seedpods
Once established, will do well on low to moderate quantities of water
Pinus specie
P. aristata (bristlecone pine), P. ponderosa (Ponderosa pine), P. mugo (mugo pine), P. nigra (Austrian pine)
Most tolerate alkaline soil as long as well-drained; does well with little water once established
Potentilla, Cinquefoil – Potentilla fruticosa
1-4 ft. high, 2-4 ft. wide
Good drought tolerance; performs best with additional moisture beyond natural precipitation
White to yellow to orange flowers throughout summer
Western Sand Cherry – Prunus besseyi
Spreading, open, airy, upright branches forming rounded or vaselike shape
3-6 ft. tall and wide
Small white flowers early summer, red fall color
Three Leaf Sumac – Rhus trilobata
Deciduous shrub to 3-6 ft., spreading 3-6 ft., fall color
Plants sucker from roots – good for erosion control on difficult sites
One of the most drought tolerant sumacs, but grows better with additional moisture
Spirea species
Deciduous shrubs to 6-8 ft, spreading 5-10 ft.; smaller varieties available
Adapts to dry conditions but best flowering with extra water
Common Lilac – Syringa vulgaris
Deciduous shrub to 8-20 ft. with spread to 6-15 ft.
Fragrant purple flowers in spring
Performs best with additional water but drought tolerant once established
Viburnum, Wayfaring Tree – Viburnum lantana
Deciduous shrub to 10-15 ft. tall, 10-15 ft. wide
Spring flowers, fall color, berrylike fruit
Low to moderate water
PERENNIALS
Hummingbird Mint – Agastache cana
Showy perennial to 2-3 ft, spreads 1.5-2 ft
Low to medium water, well-drained
Also A. foeniculum, A. barberi, A. cana
Yarrow – Achillea species
Herbaceous perennial from 2 inches to 4 ft., spreads 6 inches-3 ft.; tend to spread
Long bloom period, foliage aromatic
Well-drained soil; moist to start and dry once established
Basket-of-gold – Aurinia saxatile
Perennial to 6-18 inches tall, 6-12 inch spread
Low to moderate water, well-drained soil
Bluebell – Campanula rotundifolia
Herbaceous perennial to 6-24 inches: sprawls, self seeds, blue bell-like flowers
Low to medium water
Red Valerian, Jupiter’s Beard, Fox Brush – Centranthus rubber
Bushy clump to 2-3 ft tall 18-24 inches wide
Reddish pink to crimson flowers late spring and again in mid to late summer; attracts butterflys
Low to moderate water
Blanketflower – Gaillardia aristata
Vigorous, easy perennial, 2-3 ft. high and wide
Blooms all summer, good cut flower
Reseeds but usually not true to type
Iris hybrids
Well-drained soil; tolerates considerable drying and exposure
Blooms late spring, early summer; many colors
Catmint – Nepeta x faassenii (sterile hybrid)
Herbaceous perennial to 18 inches high, 30 inches wide
Good groundcover, lavender-blue flowers
Other varieties invasive: N. cataria (catnip), N. mussinii (catmint), N.f. ‘Blue Wonder’, N.f. ‘Six Hills Giant’
Russian Sage – Perovskia atriplicifolia
Shrubby perennial to 3-5 ft. high and 3-4 ft. wide
Sage-like aroma, silvery gray leaves, lavender-blue flowers attract bees and butterflies
Takes any soil as long as drainage is good; extremely resistant to drought and heat.
Prairie Coneflower, Mexican Hat – Ratibida columnifera
Herbaceous perennial 18-24 inches tall, 12-18 inches wide; Sunflower family
Well-drained, very little water; tolerates poor soil
Garden Sage – Salvia officinalis
Herbaceous shrublike perennial 18-24 inches tall, 12-18 inch spread
Colorfull, long-lasting flowers
Handles drought well once established
Lavender Cotton – Santolina chamaecyparissus
Subshrub, ground cover, 12-18 inches tall, spreading 12-18 inches
Tolerates heat, wind, alkaline soil
GRASSES
Blue Fescue – Festuca ovina glauca
Fine-textured, compact blue clumps
Tolerates dry conditions, looks better with some irrigation
Blue Oat Grass, Blue Avena Grass – Helictotrichon sempervirens
Ornamental perennial grass to 2-4 ft. tall in bloom, 3 ft. spread
Well-drained soil, indifferent to pH, requires moderate water
Maiden Hair Grass – Miscanthus sinensis ‘Gracillimus’
Perennial ornamental grass to 6-8 ft. tall, spreading 3-6 ft.
Most drought tolerant variety
Indian Ricegrass – Oryzopsis hymenoides
Ornamental bunch grass, 1-2 ft. high, spreads 2-3 ft.
Needs well-drained soil, tolerates drought and heat
Fountain Grass – Pennisetum alopecuroides
Ornamental grass to 2-3 ft. high, spreading 2-3 ft.
Low to moderate water, tolerates wind and heat.
Walla Walla County WSU Extension Bulletin #215 5/06 revised 5/25