Agriculture

Growing Asparagus
in West Virginia

By Lewis W. Jett, Horticulture Specialist, 2010

Asparagus is a high yielding, early season vegetable for home gardeners and commercial growers across West Virginia. Asparagus (Asparagus officinalis) which is in the onion family of vegetables, is grown as a perennial vegetable in West Virginia and can yield for 10 or more years. The asparagus plant is composed of ferns, crown and a root system (Figure 1). The ferns are not true leaves but are stems that will photosynthesize and transfer energy to the crown. The crown is a collection of rhizomes (modified roots) and lateral roots that will initiate new ferns. Spears, which are the harvested portion of the asparagus plant, are immature ferns. Thus if the spear isn’t harvested, it develops into a large fern which manufactures and stores energy in the crown for next year’s crop. Asparagus is a dioecious plant which means there are separate male and female plants. Male asparagus plants (Jersey types) produce more spears relative to female plants. Female asparagus plants produce numerous bright, red, berry-like fruits with seeds that can become volunteer weeds in the garden or field.

asparagus bunched for sale
Asparagus is sold as spears bunched and weighing approximately 1 lb.

Preparing the asparagus bed

Since asparagus is a perennial vegetable, attention should be given to choosing the best planting site. Like most vegetables, asparagus will not tolerate wet, soggy soil. Thus, choose a well-drained field or use raised beds to promote drainage. Asparagus will perform best on sandy, light textured soils. Do not rotate asparagus with vegetables in the onion family (leeks, chives, garlic) since they can transmit diseases to the asparagus planting. Choose a site with as few weeds as possible. Grow a summer (buckwheat) and fall/winter cover crop (rye, wheat) the year before you wish to plant in order to suppress weed growth and increase organic matter. Take a soil sample the fall or spring before planting for nutrient analysis. The optimal pH for asparagus is 6.5-7.0, thus lime may need to be incorporated into the soil before planting. Before planting, broadcast and plow in fertilizer to supply about 75 lbs of nitrogen (1.7lbs/1000ft2), and 25-200 lbs (0.6-4.6 lbs/1000ft2) of P2O5 and K2O per acre.

Varieties

Choose a hybrid variety for optimum yield, quality and disease tolerance (Table 1). Many of the Jersey “all male” varieties perform well in West Virginia including ‘Jersey Giant’, ‘Jersey Knight’ ‘Jersey Supreme’ and ‘UC 157 F1’ are also excellent hybrid varieties for warmer regions of the state. Open pollinated varieties such as ‘Mary Washington’ and ‘Viking’ are very good for home gardens but lack the vigor of the Jersey types for sustained commercial production.

Table 1. Recommended asparagus varieties for West Virginia

Variety Comments  
Atlas   Hybrid variety with medium to large spears that are slightly purple at the tips. Keeps a tight head in warm temperatures. Larger spears than ‘UC157’ variety.

Jersey Giant   All male hybrid variety. Green spear with purple bracts. High yields.

Jersey Knight   Emerges a week later than ‘Jersey Supreme’. Green spear with purple bracts. Does very well on heavy soils.

Jersey Supreme   Early variety. Has the potential to out yield ‘Jersey Giant’. Spears are medium sized.

UC 157 F1   Excellent yield. May not survive extremely cold winters.

Purple Passion   Burgundy colored spears with green interior. Sweeter than green asparagus. Open pollinated variety. Produces many seeds. Produces big spears, so spacing should be reduced to 8” between plants.

asparagus crowns asparagus in furrow
Figure 1. Healthy, one-year-old asparagus crowns should be planted 4-6” deep in a furrow. (Photo courtesy of C. Cantaluppi.)

Planting

Asparagus should be planted in the spring as early as the soil in the garden or field can be worked. Some varieties can be grown from seed for transplanting, but this method requires more time than using crowns. If seed is used, the seed is sown in plug trays in a greenhouse the fall before the asparagus is planted in the field. The following spring, the 3-4 month old transplants are planted, but no harvest is conducted that year or the following year in order to increase crown vigor. If crowns are used, always purchase a healthy, 1 year old crown from an inspected nursery (Table 2). Crowns will differ in size. Separate crowns by size, and plant similar-sized crowns together.

Make a 4-6” deep furrow using a “middle buster” or garden hoe. Super phosphate fertilizer (0-46-0) can be banded in the furrow (0.7 lbs/1000 ft2) or an inch of compost can be applied before planting. This is covered with an inch of soil, and the crowns are spaced 12-18” apart in the furrow. If a variety produces large diameter spears, you should reduce spacing within the row to decrease spear size. Each row should be no less than 6 feet apart so the ferns can close canopy and shade weeds during the summer. If rows are spaced too close together, spear size may be reduced. Cover the crowns with about 2” of soil, and as the ferns emerge and grow, gradually fill-in the furrow through the summer.

Growing white asparagus

White or blanched asparagus is very tender with a unique taste and is considered a rare delicacy by some. By preventing sunlight exposure to the spear, it will not produce chlorophyll. This can be done by ridging soil or straw around the crown or placing a black plastic cover over the rows.

Weed management

Weed control is the most challenging component to successful asparagus production. Asparagus is a poor competitor with weeds. On small acreages, light cultivation with a hoe may be used to remove weeds, but avoid using a rototiller or any other tillage implement which can damage the crown, reduce yields and promote diseases. Organic mulches such as grass clippings, wood chips, straw/hay or compost can be applied 4-6” thick to suppress weeds.

Several herbicides are labeled for weed control in asparagus. Glyphosate (Roundup™ 1,2) can be used as a broadcast application to control winter annual and biennial weeds early in the spring before the spears emerge. Cover crops such as rye or wheat may be spring seeded in row middles to suppress weeds. Common rock salt was once used to control shallow-rooted weeds in asparagus since asparagus is deep rooted and can tolerate some salt. However, this is no longer recommended since the salt can damage soil structure by creating a crust that impedes water infiltration.

Common Asparagus Beetle
Figure 2. Common asparagus beetle (Clemson University Extension)

Insect management

The most significant insect pest of asparagus is the asparagus beetle (Figure 2). The asparagus beetle is approximately 1/4” long with bluish black wing covers and creamy yellow spots with red borders. The asparagus beetle overwinters as an adult in crop residue or trash around the garden or field. As soon as the spears emerge in the spring, the asparagus beetle begins feeding on the spear tips and laying eggs on the spears. Both the feeding damage and the presence of eggs make the spears unmarketable. On a small scale planting, asparagus beetles can be controlled by hand removing them from the spears or ferns. However, on a larger planting, beetles can be controlled by spraying botanical or synthetic insecticides. Other potentially serious insect pests of asparagus include cut worms, grasshoppers and aphids.

Disease management

Selecting a site with good drainage and optimal pH will prevent many asparagus diseases. Crown rot can be a potentially devastating disease and is caused by over harvesting; growing on acid, waterlogged soils and excessive pest pressure. Cercospora needle blight is often observed as reddish-brown, elliptical lesions on the ferns which is followed by death of the foliage. Harvest The yield of asparagus spears in the spring is directly related to the previous year’s fern growth. Asparagus can be harvested for a limited time (2 weeks) the second year after planting crowns ( 3 years from seed transplants). Over harvesting one year can weaken the plant and decrease yields the following year. Three years after planting the crowns, asparagus can be harvested for 5-8 weeks. Each year, during the first several years of production, marketable yields will increase if the planting is managed properly. Average yields for most commercial plantings in West Virginia are 2000-2500 lbs/acre (46-57 lbs/1000 ft2).

Asparagus spears are best harvested by snapping them off by hand near ground level. Most growers prefer to snap the asparagus spears when they reach 7-9” in length in cool weather (≤ 70°F), and the spear tip is tight or 5-7” in warmer weather (≥ 70°F). Snapping will break the spear cleanly at a tender point. Cutting with a knife is generally not recommended because it may spread diseases from plant to plant. Spears with diameters greater than 7/16” are graded as “large” while spears from 5/16” are standard and 3/16” diameter spears are graded as “small”. To preserve freshness, harvest during periods of low field heat (morning or evening). Spear fresh weight is greatest in the morning. Expect to harvest every 1-3 days as the temperatures increase. Spring freezes will not harm the crowns or subsequent harvests, but can damage emerging spears. Thus emerged spears may be harvested before a predicted freeze. Asparagus has a very short shelf life and should be immersed in cold water (hydrocooled) after harvest and immediately refrigerated (36°F) if quality is to be maintained. Asparagus can be sold as 1/2-1 lb bunches. Field harvesting should cease when the majority of spears have a diameter the size of a pencil (less than 3/8”).

After harvest, the asparagus planting should be fertilized with an additional 50 lbs of nitrogen per acre (1.2 lb/1000 ft2) to stimulate summer and fall fern growth. Irrigation will be needed through the summer and early fall and during the spring harvest season.

Herbicides can be applied to after harvest to control any weed growth. Frost will desiccate the ferns, and they can then be bush-hogged in late fall or early winter. Do not mow ferns in early fall while they are still green because this will reduce the following spring harvest. The mulch can be raked to the row middles the following spring (early April), and spears will emerge for another harvest season.

Table 3. Some suppliers of asparagus seed and crowns2

Nourse Farms, Inc.
41 River Rd.
South Deerfield, MA 01373
413-665-2658
www.noursefarms.com

Krohne Plant Farms
65295 CR 342
Hartford, MI 49057
616-424-5423

Jersey Asparagus Farms, Inc.,
105 Porchtown Rd.,
Pittsgrove, NJ 08318
856-358-2548
www.jerseyasparagus.com

Ron Richter Farms
Rt. 2
90487 60th St.
Decatur, MI 49045
616-423-7339

Daisy Farms
91098 60th St.,
Decatur, MI 49045
616-782-6321
www.daisyfarms.net

California Asparagus, Seeds &
Transplants Inc.
2815 Anza Ave.
Davis, CA 95616
530-753-2437
www.calif-asparagus-seed.com


1“Roundup” is a registered trademark of Monsanto.

2The listing of business and product names are not endorsements by West Virginia University of any business or product to the exclusion of another.