The tasty spears of this hardy perennial push up from heavy root masses from early spring until warm weather arrives and occasionally through midsummer. (Asparagus needs a winter dormancy period to thrive.) Mature asparagus plants look completely unlike the spears; they reach from 4 to 6 feet in height and billow out to a width of 3 feet. These feathery, decorative plumes should be left on the plant until they have begun to dry in late autumn; they manufacture the food reserves that maintain strong crowns from year to year. Cut the stems to the ground only after the foliage turns brown.
Although asparagus takes several years to come into full production, the plants are very long lived—up to 20 years or more. Two dozen plants should yield enough spears for a small family.
How to plant. Since three years are required to produce spears from seed-grown plants, most gardeners prefer to start from roots. Roots are available during the late winter in Western states and can be planted as early as they are available. In other areas, mail order is the usual source. Plant the roots as soon as you receive them.
Asparagus plants need lots of room and full sun. Plant them at the back of the garden or along a fence where the tall foliage won’t be in the way. Because the plants will be in place for many years, the soil should be broken up to a depth of 18 inches and large volumes of organic matter, such as well-rotted manure, should be worked in thoroughly. Don’t skimp on the width of the bed; the prepared soil should extend 18 inches beyond the crowns. Mixing in organic matter should raise the bed 2 to 3 inches above the surrounding soil; this improves drainage.
For each crown, dig a hole 5 to 8 inches deep in the prepared bed and fill it with water. Pile a cone of loose soil 3 to 4 inches high in the center of the hole. Set the crown in the hole and spread out the fleshy roots. Fill the hole with soil and firm it down lightly around the roots. Water the crown again.
Care. Cultivate only in the top inch of the soil so you don’t injure the network of roots. Pull weeds by hand before they get started in the bed, where they will be difficult to pull out without injuring the asparagus roots.
Perforated sprinkler hoses provide an excellent device for the deep watering needed by asparagus, since beds are too wide for basins or furrows. Let the sprinkler run for several hours every week or two during dry weather.
Feed with a complete fertilizer high in nitrogen when plants put on a growth spurt—usually around midsummer. When you remove the brown foliage in the fall, add a mulch of 2 to 3 inches of coarse organic matter, such as well-rotted manure. Do not use peat moss or leaves as a mulch; they form a crust or pack down, preventing moisture from penetrating the bed and hindering emerging spears.
Pests. The organic mulch over the beds makes a good hiding place for snails, slugs, sowbugs, and earwigs.