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WSU Snohomish County Extension office has moved!

Our office is now located in the Snohomish County Parks & Recreation Administration Office at Willis Tucker Park, 6705 Puget Park Drive, Snohomish, 98296.

Growing the Nightshade (Tomato/Potato/Pepper) Family

Posted by kate.ryan | August 25, 2015

Maritime NW Favorite Variety list

This list of nightshade family variety favorites for Maritime NW.pdf was gathered from the suggestions and experiences of our Snohomish County Growing Groceries and Master Gardener volunteers.


Potatoes can be planted from either whole or cut seed tubers. Select only certified seed potatoes to minimize disease and to avoid sprout inhibitors, which typically are used on potatoes available in our grocers’ produce section. Select cultivars that you like and fit your culinary needs. Seed potatoes are planted at a depth of about 4 to 5 inches, spaced about 12 inches apart and in rows 36 inches apart. Hills can be formed at planting or after the potatoes have emerged. The hill provides protection to the developing tubers from the sun and aids in water management.

Moisture is important for potatoes at all stages of growth, and the developing plants will access moisture primarily from the top 12 inches of soil. When the rainfall is inadequate, irrigation should be applied about every five days and the soil dampened to a depth of about 2 feet.

Potatoes typically are fertilized in the home garden at planting using a banded application of a typical blend, such as 15-30-15, about 2 inches to the side and 2 inches below the seed piece. A light application (side-dress) of nitrogen may be appropriate midseason if plants are yellowing. Most pests in the home garden can be addressed without the use of pesticides; however, if late blight is present in the area, a preventative fungicidal program would be appropriate.

Potatoes can be harvested through the growing season as new potatoes or in the fall after the plants have matured. Use new potatoes quickly after digging due to the rapid loss of moisture from the tender skins. For storage, temperatures in the range of 38 to 40 degrees are typical.


Plant tomatoes at least 2 to 4 inches deeper than the seedling roots. New roots will emerge along the buried stem and result in a sturdy plant that is able to mine more nutrients and water from the soil. Tomatoes can be planted one per square foot or conventionally, with adequate spacing between plants in a row. Vine-type (listed in catalogs as Indeterminate) will need more space unless they are staked. Staked tomatoes will result typically in a smaller yield, but higher quality fruit. Bush tomatoes (Determinate) grow to a specific size, bear flowers and fruit, then stop. Where space is a premium, the determinate tomato cultivars may be the way to go. They also lend themselves well to container gardening.

Growth can be encouraged through the season with regular fertilizations of a material high in phosphorus. Never use lawn fertilizers for garden crops, especially any members of this nightshade family. Cultivation around tomato plants should be carried out with care, if at all. The roots are near the surface, and the damage to the roots often will result in a physiological disorder known as Blossom End-Rot (BER) to the developing fruit. Generally, this is noted on just the initially ripening fruits, and while unattractive, if the gardener wants to cut out the affected area, the rest of the tomato certainly is edible.

Harvest tomatoes when they have developed a deep red color (or a color that is typical for a particular cultivar) and store them at room temperature if they are not going to be consumed right away. Refrigerating tomatoes ruins the good flavor that typically is characteristic of garden-fresh tomatoes.

For detailed growing instructions, we recommend reading Growing Tomatoes in Home Gardens.


Since pepper plants are more sensitive to temperature fluctuations than tomatoes, setting them out early generally is not a good idea. Hardened-off tomatoes may be tolerant somewhat to chilling temperatures, where peppers are not. They typically grow with less vigor and require higher temperatures than tomato plants. The sweet peppers, also known as “bells,” are most popular with Americans. Hot or chili types are increasingly being planted in our gardens as Americans become more acquainted with more pungent tastes in their food.

Peppers are spaced typically 18 to 24 inches in the row, and as with tomatoes, gardeners need to exercise care when cultivating near the plants. If weeds are a problem in a pepper planting, we highly recommend hand pulling at the earliest stage. Most of the bell (sweet) peppers are harvested green and immature, but when they are full-sized and firm. If the season will allow them to do so, the peppers will ripen and be sweeter and higher in vitamin content, often changing in color from green to red. Unlike tomatoes, harvested peppers can be stored in a vegetable crisper for up to two weeks without significant loss in quality.


Of all the members of the nightshade vegetable family, the eggplant would benefit most from the use of plastic mulch to get the soil temperature up and keep it there. Plants may be planted in staggered double rows on each strip of plastic, spaced 18 inches apart. The fruits of eggplant are edible from the time they are one-third grown until ripe. They remain edible for several weeks after they become fully grown and colored with a shiny skin. Like squash and cucumber, they will continue to bear if they are harvested when of adequate size and color until an autumn frost stops everything. They do require hot summer temperatures and at least 100 days to successfully produce fruits.