Plant care & info

Asparagus yields best in full sun (at least six hours of direct sun), but tolerates light shade. An area sheltered from strong winds is preferred. Provide well-drained soil with a neutral pH.

Plant asparagus roots in spring as soon as the soil is dry enough to dig an 8” deep trench without large clods. Preparing a raised area, with or without sides, can help this occur earlier in the year. If the crowns look or feel dry, soak them in water for 30 minutes prior to planting.

Create a trench 12” wide and 8” deep. Mix in 1-2” of compost in the trench—along with lime and bone meal. Also mix about 1/3 compost with the soil that you dug out of the trench. To help all the roots contact the soil directly, place crowns (roots) on top of individual mounds of soil created inside the trench.

Make sure that the crowns do not touch one another, as the roots tend to mold where they touch. Plant crowns 12” apart, or farther if needed, to keep them from touching. Try to position the top of the crowns so that they are about 2” below the soil surface.

Cover crowns with the remaining soil, but no more than 2” over the top of the crowns. If it looks like they will be deeper than 2”, reserve the extra soil and add it after shoots have appeared and are 6-8” tall. Burying too deep can increase the chances of crowns rotting before they sprout. Water at planting time, regardless of how wet the soil appears.

During the initial growth period, irrigate well and allow the soil to dry out a bit between waterings. Irrigate deeply about once a week for the first two years. Once the bed is well established, asparagus is very drought tolerant.

Weeding is essential for a healthy asparagus patch, don’t let your new plants compete with weeds for nutrients. Asparagus does not need fertilizing once the bed is well established (usually by the third year). However, it will still benefit from about 1⁄2” of compost on top of the crowns to keep them below the soil surface.

Apply lime every few years to continually sweeten the soil. Cut back yellow foliage every fall. It is difficult to move the plants to a new space should disease problems occur, so fall clean up in the asparagus bed is vital. Cut all yellow stalks to the ground and rake away all the fallen foliage.

Allow plants to grow undisturbed their first year. Harvest lightly the next spring, cutting only the spears which are larger in diameter than a pencil, for no more than 4-6 weeks. Be careful not to cut below the soil level. By the third year, you will have a full harvest season of 8-12 weeks.

In cooler northern climates (Portland included) you can extend the season using the mother-stalk method during the third year. Harvest spears for 2 weeks and then allow two or three spears from each crown to grow and produce foliage. This initially slows production for a few weeks, but it will pick up once the energy produced by the foliage kicks in. You can keep harvesting for 10 weeks.

Snails and slugs chew on young spears and foliage of mature plants. This can substantially diminish your harvest! Put out preventative slug traps or bait before you expect them to sprout (late Feb.)

Cutworms and Armyworms feed on spears near the soil line. Beneficial nematodes applied in fall or early spring can help control the larval population. Spinosad helps control the worm population.

Asparagus Beetles chew small holes in the spears and the tips of the damaged spears often curl. Cover beds with floating row covers, and securely seal the edges in early spring to keep out beetles. Organic sprays such as insecticidal soap, pyrethrins and spinosad all help control populations.

Gray Mold shows as brown or gray fuzzy growth on spears. It is especially prevalent in cool, wet weather. Remove and destroy infected spears and then remove mulch. This will help soil dry out. Neem oil can help protect healthy plant tissue in warm weather.

Fusarium Wilt appears as weak, brown spears. Fusarium wilt is a permanent soil borne fungus. The best course of action is to remove and destroy the infected patch. Start a new bed with fresh crowns in a different location.

Rust (Needle Blight) appears as the feathery foliage losing “needles” very early. Upon closer inspection the foliage will exhibit orange spots. In cold, wet weather it may appear as gray spots with a purple edge. Cut down infected fronds and destroy them. Spray healthy foliage with neem oil or other fungicide approved for edible crops.

Asparagus is a long-lived perennial plant that can produce delicious spears every spring with only a little maintenance; but it takes 2-3 years to come into full production. Asparagus is commonly grown from 2 year old crowns (roots), which may reach bearing size somewhat faster than seeds.

TOP ASPARAGUS VARIETIES

Jersey Knight

This all-male asparagus variety yields the highest quality spears of the Jersey hybrids. It has performed exceptionally well in trials all across the U.S. Each mature plant produces 7-9 choice 7-10” spears tipped with a purplish blush. At that length, the spear diameter is between 3/8-3/4”. Highly resistant to rust, fusarium, root rot, crown rot, and cercospora. Easily overwinters in the maritime Northwest.

Note: All-male varieties have been bred with the idea that other varieties spend significant energy each year forming and ripening seed, so varieties that can avoid that will have more energy for shoot growth. Furthermore, asparagus patches that reseed become denser over time, eventually limiting yield as a result of root competition. All male varieties make no seed and never produce more plants. This is good for the long term health of asparagus patches, but bad for expanding a young patch or giving plants to a friend. Mixing all male varieties with varieties that have male and female plants eliminates the benefits.

Mary Washington

This variety yields long, straight, thick and heavy shoots. They’re a rich, dark green, slightly tinged purple at the tightly folded tips. Mary Washington produces heavy yields, with 60 day cutting season. Holds a tight bud longer than most. Somewhat rust resistant.

Sweet Purple

This newer type of asparagus has many similar characteristics to the green varieties, but offers something new for the connoisseur. Crowns are both male and female. Deep burgundy spears have a 20% higher sugar content. Because of this extra sweetness, this vegetable is often eaten raw or as a salad garnish. When cooked, the sweetness gives the asparagus a mild, nutty flavor.

Spears are generally larger, more tender, and less stringy than their green counterpart. This allows the cook to use the entire spear with little waste. However, purple asparagus require excellent drainage to overwinter in the Pacific Northwest—so be sure to plant in a raised area or on a slope, and amend heavily with pumice before planting.