By Kathleen Cue, Nebraska Extension Horticulture Educator
Cooks love the earliness that fresh asparagus provides. Gardeners love it because it’s perennial and relatively worry-free. If you’ve not grown asparagus, this spring would be a good time to plant a few crowns to find out for yourself just how easy it is to grow.
Asparagus can be started in one of two ways. Seeds are an economical way to go but add an extra year onto when harvest can begin. Asparagus can also be started from year-old crowns purchased from garden centers, box stores or catalog companies. ‘Mary Washington’ is an asparagus variety that has been around since 1949 and is still readily found today. The ‘Jersey’ series of asparagus, consisting of ‘Jersey Knight’ and ‘Jersey Giant’ are highly touted but lack hardiness when temperatures are below -30° F and snow cover is minimal. Newer varieties better suited to our winters include ‘Purple Passion’ and ‘Viking KB-3’.
Asparagus is a dioecious species, meaning there are male plants and female plants. Female plants produce red “berries” that drop to the ground, seeding new plants into unexpected places like creeks, ditches, and roadsides. If not sprayed with a pesticide, spears can be harvested from these wild plants. (My brother has a list of locations of wild asparagus and jealously keeps it secret!) While the berries are not poisonous, they are inedible. Male plants tend to live longer and produce more spears.
Because asparagus is a long-lived plant, care should be given to soil preparation. A pH of 6.5-7.0 is best for good growth. Sulfur may be added to bring the pH lower if the pH is above 7.0. Asparagus plants appreciate a deep loamy soil so work compost into the site if the soil is sandy or clayey. Soils in our area tend to be abundant in phosphorus and potassium, so a 30-0-0 fertilizer applied at of a rate of ½ pound per 100 square feet provides the nutrition for good growth.
To plant asparagus crowns, dig a trench 6-8 inches deep and 12 inches wide. Spread out the roots around the crown and add two inches of soil. (More soil is added as plants grow.) Crowns should be spaced 12-18 inches apart in rows 5 feet apart.
Weeds and the asparagus beetle are two common problems. Keep in mind that tilling to remove weeds has the potential to damage asparagus crowns too. Hand-pulling weeds and mulching with shredded newspapers or wood chips keeps weed numbers low while plants are establishing. Once the stems develop ferns, the plants will shade out would-be competitors. The asparagus beetle, both the adults and the immatures, feed on the spears, stems, and foliage of asparagus, causing bending or twisting of the spears, along with brown spots from the feeding site. If damage from the asparagus beetle warrants control measures, use an insecticide labeled for use on edible crops such as insecticidal soap or spinosad.
Asparagus can be harvested during its third growing season. Bend the spears to snap them off or use a knife to do a clean cut. Once most of the patch has more pencil-sized spears than plump ones, it’s time to quit harvesting and let plants re-build their reserves. Cut the stems and ferns back to the ground in the fall after the entire plant has turned brown. This allows the plant time to transport carbohydrates from the leaves into the root system. This also removes overwintering eggs from the asparagus beetle.
More information may be found here: https://extension.umn.edu/vegetables/growing-asparagus .
Nebraska Extension Master Gardeners can answer your gardening and plant questions! The horticulture helpline is available for questions from the public at these dates and times:
Mondays, 9 a.m. to 12:00 noon, Washington County Extension, 402.426.9455
Tuesdays, 1:00 to 3:00 p.m., Cuming County Extension, 402.372.6006
Wednesdays and Fridays, 9:00 a.m. to 12:00 noon, Dodge County Extension, 402.727.2775