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Answers to Frequently Asked Asparagus Questions
This article was published originally on 3/26/2004
Asparagus is one of the most popular vegetables in the home garden. If given good care, an asparagus planting may be productive for 15 or more years. Answers to several frequently asked questions on asparagus care and maintenance are provided below.
When and how do I plant an asparagus bed?
A. Early spring (April) is the best time to plant an asparagus bed in Iowa. Since asparagus is a perennial crop, carefully consider possible sites. Asparagus performs best in well-drained soils in full sun. In poorly drained sites, raised beds may be a solution. Avoid shady sites near large trees and buildings.
Asparagus can be grown from seeds. However, asparagus is most commonly established by planting one-year-old asparagus plants or crowns. Asparagus crowns should be planted in shallow trenches or furrows. The planting depth depends on the soil type. Asparagus crowns should be planted 6 to 8 inches deep in light, sandy soils, but only 4 inches deep in heavier soils. A small amount of manure can be worked into the soil at the bottom of the trench before planting. Space the 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 commonly done in the past, it's not necessary to gradually fill in the furrow as the plants grow.) Male hybrid asparagus varieties are more productive and longer-lived than other varieties. Suggested male asparagus varieties for Iowa include Jersey Giant, Jersey Knight, and Jersey King.
Is it possible to move an established asparagus bed?
A. The roots of established asparagus plants are deep and quite extensive. As a result, transplanting attempts are usually unsuccessful. Large, old plants will be severely injured during the transplanting procedure. Some may actually die. Those that survive may never produce a good crop. The best way to establish an asparagus planting is to purchase one-year-old plants or crowns from a garden center or mail-order nursery.
When can I start harvesting my asparagus?
A. Asparagus plants should be allowed to become well established before any spears are harvested. No spears should be harvested during the first growing season. Asparagus can be harvested over a three to four week period during its second growing season. In following years, asparagus plantings can be harvested until early to mid-June. Harvest asparagus by cutting or snapping the spears when they reach a height of 6 to 8 inches.
When should I stop harvesting asparagus?
A. Discontinue harvesting well established asparagus plantings in early June in southern Iowa and mid-June in northern portions of the state. If harvested over a longer period, the plants may be weakened and less productive in future years. Allow the asparagus stalks to grow after the last harvest.
When should I fertilize my asparagus bed?
A. Asparagus can be fertilized in early spring before the spears emerge. An application of 1 to 1.5 pounds of an all-purpose garden fertilizer, such as 10-10-10, per 100 square feet should be adequate. Asparagus can also be fertilized after the last harvest in June. Using a nitrogen fertilizer, apply .10 pound of actual nitrogen per 100 square feet. For example, an application of .3 pound of ammonium nitrate (34-0-0) per 100 square feet will supply .10 pound of actual nitrogen.
How do I control weeds in my asparagus planting?
A. The best way to control weeds in a home asparagus planting is by hoeing or tilling. Hoe or till the planting periodically in spring and early summer. Cultivate lightly to avoid damage to emerging spears.
How do I control perennial grasses in my asparagus bed?
A. Because of their extensive root systems, perennial grasses can be difficult to control in asparagus. Hoeing or tilling will simply not work. The best option is to spot treat with glyphosate (Roundup) immediately after the last harvest of the season. During the last harvest, cut or snap off all asparagus spears at the soil surface. Then immediately spot treat the grass-infested areas with Roundup. Do not allow Roundup to get on any emerged asparagus growth as injury or death may result.
Is salt beneficial to asparagus?
A. Applying salt to an asparagus planting is not beneficial. In years past, some gardeners used salt to control weeds in asparagus. However, salt is not effective in controlling many weeds, especially grasses. Plus, continued use of salt may result in high salt levels in the soil. High levels of salt may actually damage the asparagus planting. In the home garden, shallow hoeing or tilling is the best way to control most weeds.
When can the asparagus foliage be cut back?
A. It's imperative not to cut back the asparagus foliage while it is still green. To produce a good crop next spring, the asparagus plants must manufacture and store adequate levels of food in their roots and crowns. The dead (brown) tops can be cut back in late fall. However, it's generally recommended that the dead top growth be allowed to stand over winter. The dead growth will catch and hold snow. The snow insulates the asparagus crowns and also provides moisture.
Last updated 4/2/2004 by John VanDyk
Year of Publication:
IC-491(5) -- March 26, 2004