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Growing Asparagus in the Home Garden
submitted by Sarah Browning, UNL Extension Educator
Asparagus is a well-loved spring vegetable, offering one of the earliest signs for winter's end and the beginning of a new growing season. It's not difficult to grow and once established can be harvested for many years. Plantings may be productive for 15 years or more with proper establishment and care.
Site Selection & Preparation: Because asparagus is one of the few perennial plants found in the vegetable garden and will be growing on the same site for many years, choose a location in the garden carefully. Asparagus grows well on almost any soil, as long as it is deep, well drained and preferably has a soil pH range of 6.5-7.5. Water logged soils will lead to root rot, and since mature plant root systems are at least 6 feet deep, also avoid sites with shallow water tables. Pick a site at the side or end of the vegetable garden, where plants won't be disturbed by tilling and to avoid shading shorter vegetables during the growing season.
It's worthwhile to take the time to prepare the soil deeply and amend with organic matter, which will increase the water holding capacity of sandy soils and improve water drainage in heavy soil. Till or spade 3 to 4 inches of compost into the soil at a depth of 8 to 10 inches. At the same time, incorporate 2 lbs. per 100 sq. ft. of a general purpose fertilizer, such as 10-10-10 or 12-12-12.
Finally, weed control is a common problem in the asparagus bed. Be sure to kill all perennial weeds in the area before planting. Mulch, plus pre- and post emergent herbicides can be used for long term weed control in years to come.
Plant Selection: Asparagus is planted from crowns, which are one-year old dormant root systems. Choose a male cultivar, such as 'Jersey Supreme', 'Jersey Giant' or 'UC 157', for the highest yield. Female cultivars like 'Mary Washington', 'Martha Washington', or 'Purple Passion' will fewer, thicker stems and a lower total yield due to energy diverted to seed production. Plus seedling asparagus plants can become a weed problem when using female cultivars.
Planting: Don't plant until the soil is at least 50 degrees. When the time is right for planting, dig a trench approximately 6 inches deep and 12 to 18 inches wide. Space rows 4 to 5 feet apart. Spread 1 lb. of triple super phosphate (0-46-0) per 50 feet of row in the bottom of each trench. Place the crowns bud side up in the trench about 1Â½ feet apart, spreading the roots out across the trench.
Traditionally, the crowns are then covered with 2 inches of soil. When new shoots emerge, 2 additional inches are added being careful to keep some of the new growth exposed. This process is repeated until the soil is filled to the top of the trench. While most people still plant asparagus this way, new studies have shown that this is not necessary and the planting trench can be completely filled with soil after planting. Either way, do not compact the soil over the crowns.
Water the new planting thoroughly. Once established, asparagus is quite drought tolerant, but additional irrigation may be needed during the establishment year based on this summer's rainfall.
Maintenance: Do not harvest any spears from your asparagus plants during the first year. Plants may be harvested lightly, for about 3 weeks, during the second year. Harvest when the spears are 6 to 10 inches above the ground but before the heads open, by cutting or snapping the spears off at the soil line.
The third year plants may be harvested for 6 to 8 weeks. Stop harvesting anytime the majority of spears are less than 3/8" diameter.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office