Growing Asparagus in West Virginia

Growing asparagus requires a little more patience than most vegetable crops. While it typically takes 2 to 3 years of production to yield a significant crop, once it’s established, asparagus requires little ongoing care and plants can remain productive for more than 15 years. Asparagus is delicious and nutritious, as well as a high-value crop that will bear early in the season and can be preserved for consumption throughout the year. Asparagus consists of roots, crown buds, and tops known as ferns. Young, succulent shoots are formed in spring from the crowns. Later in the summer after shoots have formed, asparagus will grow lacy fern tops several feet high.

Production

Asparagus needs f ull sun but is most productive in areas with cool winters. Once established, plants can tolerate some freezing in the winter. Since plants can be productive for several years, it is best to choose a location with well-drained soil that will not be disturbed often, perhaps even away from the garden. A separate growing area is also helpful because the tall ferns that grow in summer can shade other plants. Asparagus is especially well suited to raised beds, which can control the spread of the plant. Asparagus can be planted in beds about 4 feet wide so that it can be harvested from both sides, or planted in rows spaced 5 feet apart with seedlings/crowns spaced 8 to 12 inches apart. Adequate space allows for extensive root development. Weed control is essential to prevent competition with young plants. Plants can be mulched 3 inches deep to conserve water, provide more frost protection, and help control weeds.

Asparagus can be produced from seeds or crowns, but starting from seeds will require an extra year of production compared to planting crowns. Choose stock from a reputable grower or nursery to decrease the chance of disease contamination. Seeds may be slow to germinate, so they can be started indoors in peat pots and thinned to 1 plant per pot. Seedlings can then be transplanted after the danger of frost in late spring or early summer. They can be transplanted directly to the final location, or they can be raised in another area to harvest the crowns early the next year and then transplanted to the final location.

Transplanting 1- or 2-year-old crowns instead can decrease the number of years before substantial harvest. Choose healthy crowns that appear solid and strong. A few weeks before the last frost, dig a 6-inch-deep trench and plant crowns 12 to 18 inches apart within the row and cover with 3 inches of soil, mounding slightly around each crown. Deeper planting will yield fewer but larger asparagus spears, while shallow plantings will yield more small spears and can lead to increased frost damage. Continue adding more soil over the crown every few weeks as it sprouts and grows.

Spears will emerge when soil temperatures are 40 F to 50 F in early spring, and the harvest period is typically up to 8 weeks in May and June. Asparagus should not be harvested in the first year as it will damage the plant’s overall productivity; young plants need time to establish a root system and store nutrients and energy. Plantings may be harvested lightly the 2nd year and more significantly the 3rd year. To extend the harvest season by a few weeks, plant asparagus at different depths (3 inches, 6 inches, and 9 inches) or remove the mulch from half the plants. Either will help provide a second crop later in the summer.

Soil

Proper soil preparation will increase the chance of successful production. Till the ground at least 8 inches and remove weeds and their roots. Asparagus thrives in loose, fertile, well-drained soil that is high in organic matter to allow the development of a strong root system. Soil quality and water retention can be improved by adding compost, but avoid raw manure or green compost as they can introduce weed seeds and harmful bacteria. Work the soil, adding compost and fertilizer based upon soil test recommendations. Free soil testing is available to West Virginia residents from the WVU Soil Testing Lab. The ideal pH is neutral or slightly acidic, around 6.5 to 7.

In winter, after the foliage yellows, cut ferns to 2 inches and add up to 6 inches of mulch or compost to protect the plants and enrich the soil. Ferns should be removed and destroyed to reduce the incidence of disease. This should be completed once the foliage begins to die back but before the asparagus sets berries, as their seeds can cause new seedlings to compete with the established ones. Many hybrid cultivars yield male-only plants, which will prevent seed production and increase yield, as female plants expend energy for reproduction. Allowing the ferns to remain on the plant until frost allows time for the plant to store energy and move it to the crowns. Removal and destruction of the ferns will decrease the incidence of insect pests. After ferns are removed in the fall, apply more compost and fertilizer as indicated by the soil test. Phosphorus and potassium will help with energy production and transport, and root development. Nitrogen encourages growth and breaks down in the soil quickly, so it should be applied in spring.

Watering

Crowns can be soaked for a few minutes before planting. Once planted, water seedlings or crowns regularly to ensure establishment. Do not saturate the soil, as waterlogged soil can increase rot and damage roots. Avoid watering late in the day or on the top of plants, as this can increase the chance of disease. Once established, plants have strong roots and will only need watered during dry conditions.

Harvest and Storage

Harvest asparagus when spears reach the diameter of a pencil or greater, are 6 to 8 inches tall, and tips begin opening. Carefully snap sprouts at the soil surface. Harvest in early morning if possible, as plant tissue is hotter later in the day and might not keep as long. Avoid pulling on or injuring the crown as damage will decrease productivity. Early in the season, beds or rows can be harvested every few days, then every day at the peak of the season. Harvesting too late will yield tough, overly mature spears. Once harvested, spears should be gently washed, dried on a paper towel, then refrigerated. Asparagus can dry out easily; wrap the spears in a damp paper towel before placing them in a storage bag to seal in moisture. You can also place asparagus in jars with the tips sticking upward and fill with 1 inch of cool water. If the cut end has already started to dry out, remove a half inch off the end before storing in a bag or jar. Asparagus should be eaten or processed within 3 to 5 days for the best quality.

Varieties Selected for West Virginia

Newer asparagus varieties are often hybrid, male-only plants which have increased production. Many are cold-tolerant and resistant to rust and Fusarium as well.

Green asparagus and purple asparagus are different varieties. Green plants get their color from chlorophyll used in the photosynthetic process. Purple asparagus has higher levels of anthocyanins, pigments which are also found in blueberries and purple cabbage. High heat can break down these dark pigments and reveal the green color from chlorophyll, so purple asparagus may turn green if cooked for long enough. White asparagus has fewer antioxidants but can be considered a delicacy. White asparagus is a green asparagus variety that is continually covered with soil as it grows. Being essentially grown underground or covered, it is not exposed to sunlight, so chlorophyll is not produced. Taste depends upon variety, but white asparagus typically has a light nutty flavor, whereas purple asparagus is often slightly sweeter and less earthy than green varieties.

* Indicates hybrid variety; RT = Rust Tolerant; FT = Fusarium Tolerant. CBT =Cercospora Blight Tolerant; HT = Heat Tolerant

Nutrition

Asparagus is a low-calorie, nutrient-dense vegetable rich in vitamins, minerals, fiber, and antioxidants, making it highly beneficial for overall health. One serving (3 to 5 spears depending upon size) provides 2 grams of dietary fiber, 2 grams of protein, 10% of the daily Vitamin A recommended daily intake, 25% of the Vitamin C requirement, 51% of the vitamin K requirement, and several forms of vitamin B in only 25 calories. When compared to green asparagus, purple varieties have increased antioxidants (anthocyanins), which give it a deep color and increased anti-inflammatory benefits. White asparagus has significantly lower antioxidant levels than colored asparagus.

Cooking

Before consuming, rinse asparagus and trim the cut end if it is tough. Asparagus can be eaten raw in salads, pasta, or by itself. Generally, it is best when only cooked lightly to maintain a tender but firm texture. Overcooking can cause asparagus to have a mushy texture and destroy some nutrients. Asparagus can be steamed or lightly blanched. The fresh natural flavor can absorb seasoning such as herbs or garlic when heated. Season and toss with olive oil or butter before grilling, roasting, broiling, or sautéing.

Preserving

Asparagus will stay fresh in the refrigerator for 3 to 5 days. Fresh, young, tender, and firm spears will stand up best to preservation. Wash asparagus and trim the cut end. Freezing is the best option for asparagus preservation. Lightly blanch by putting spears in boiling water for 2 to 4 minutes, depending upon spear diameter. Then quickly place in ice water to stop the cooking process. Dry spears and place in zip-lock or vacuum-sealed bags and freeze. Blanching and sealing the bags correctly can help prevent freezer burn. Consume frozen asparagus within 12 months.

To can asparagus, either hot pack jars (blanched asparagus and water) or raw pack (raw asparagus and water), season with salt, then leave 1 inch of headspace at the top of the jars. Asparagus must be processed under pressure as it is a low-acid vegetable. Water bath canning can be used if pickling asparagus, using a seasoned vinegar brine. Jars should be checked for the seal and spoilage before consuming.

Insects, Diseases, and Other Issues

  Jodi Shelton, WVU Extension Agent  – Mercer County

References

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