Yard and Garden: Establish an asparagus patch

AMES — Asparagus, one of the most popular spring vegetables, is a hardy perennial plant that produces edible spears. Plantings will produce good crops for 15 to 20 years if planted in a favorable location and good cultural practices are followed. Iowa State University Extension and Outreach horticulturists offer tips on suitable locations, good varieties and proper planting of asparagus. For more information, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

What would be a suitable
planting site for asparagus?

Carefully consider possible planting sites for asparagus, as a well-maintained planting in a favorable location can be productive for 15 to 20 years. Asparagus performs best in well-drained soils in full sun. Avoid poorly drained, wet sites. Phytophthora crown rot can be a problem in poorly drained, wet locations. Raised beds are a good planting option for gardeners with poorly drained soils. Planting sites should receive at least six hours of direct sun each day. Avoid shady sites near trees. A location at the end of the vegetable garden (that doesn’t interfere with annual garden tillage and other cultural practices) is a good site for many home gardeners.

What are some good asparagus varieties for Iowa?

Asparagus is dioecious. Dioecious plants produce separate male and female plants. Male asparagus plants live longer and are more productive than female plants. Excellent predominantly male asparagus cultivars include ‘Jersey Giant,’ ‘Jersey Knight,’ ‘Jersey King’ and ‘Jersey Supreme.’ ‘Mary Washington’ and ‘Martha Washington’ are good standard asparagus cultivars. (A planting of ‘Mary Washington’ or ‘Martha Washington’ has an equal number of male and female plants.) ‘Purple Passion’ and ‘Sweet Purple’ are unique cultivars with deep burgundy or purple shears. (The spears of ‘Purple Passion’ and ‘Sweet Purple’ turn green when cooked.) One-year-old asparagus crowns can be purchased at garden centers and mail-order nurseries.

What is the proper way
to plant asparagus?

Early spring is the best time to plant asparagus in Iowa. Asparagus crowns should be planted in shallow trenches or furrows. The planting depth depends on the soil type. Asparagus crowns should be planted 8 to 10 inches deep in light, sandy soils but only 6 to 8 inches deep in heavier soils. A small amount of well-rotted barnyard manure can be worked into the soil at the bottom of the trench before planting. Space crowns 12 to 18 inches apart in rows that are 4 to 5 feet apart. Spread the roots out in the trench with the buds pointing upward. After planting, completely fill in the trench with soil. (Though a common practice in the past, it is not necessary to gradually fill in the furrow as the plants grow.)

When can I begin to
harvest asparagus?

Asparagus should be allowed to become well established after planting before any spears are harvested. Do not harvest asparagus for the first two years after planting. In the third and following years, asparagus can be harvested until early to mid-June in Iowa.