Growing Asparagus Information
Asparagus is a high-yielding, early-season vegetable for home gardeners, which is in the onion family of vegetables, is grown as a perennial vegetable in the UK and can yield for 10 or more years. The asparagus plant is composed of ferns, crown and a root system. The ferns are not true leaves but are stems that photosynthesize and transfer energy to the crown. The crown is a collection of rhizomes (modified stem) and lateral roots that initiate new ferns. Spears, which are the harvested portion of the asparagus plant, are immature ferns. Thus, if the spear is not 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 that there are separate male and female plants. Male asparagus plants (Jersey types) produce more spears than female plants do. Female asparagus plants produce numerous bright, red, berrylike fruits with seeds that can become volunteer weeds in the garden or field.
Preparing the asparagus bed is important as 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. 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) because they can transmit diseases to the asparagus planting. Choose a site with as few weeds as possible. Growing a cover crop during the summer (buckwheat) and the autumn and winter (wheat) the year before you wish to plant asparagus will suppress weed growth and increase organic matter in the soil. Take a soil sample in the autumn or spring before planting for nutrient analysis. The optimal pH for asparagus is 6.5 to 7.0; lime may need to be incorporated into the soil before planting. Before planting, spread and dig in.
Commercial growers chose a F1 hybrid variety for optimum yield, quality and disease tolerance. Many of the Jersey "all male" varieties perform well in the UK, including our very own, Jersey Knight. Open pollinated varieties such as 'Mary Washington' and 'Connovers Colossal' are very good for home gardens but lack the vigour of the Jersey F1ís.
Asparagus crowns should be planted in the spring as early as the soil in the garden or field can be worked. In southern counties this corresponds with late March or early April, while growers in central and northern counties can plant asparagus from early to mid April.
Our varieties can be grown from seed for transplanting during spring summer or autumn, but no harvest is conducted that year or the following year in order to increase crown vigour.
Crowns will differ in size. Separate crowns by size and plant similar-sized crowns together; this encourages uniform growth. If crowns cannot be planted immediately, store them in a refrigerator.
Make a 4- to 6-inch-deep furrow using a garden hoe. Well rotted manure or worm cast compost can be spread in the furrow an inch of compost can be applied before planting. This is covered with an inch of soil, and the crowns are spaced 12 to 18 inches 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 5 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 inches of soil, and as the ferns emerge and grow, gradually fill in the furrow through the summer.
Plants that are stressed by drought can become weak and susceptible to insect, disease and weed pressure. Growers should be prepared to irrigate new asparagus plantings for the first two or three seasons after establishment, and each year during the spring harvest season in case of a spring drought. Drought stress after harvest can reduce yields for the following season.
Weed control is the most challenging component of successful asparagus production. Asparagus is a poor competitor with weeds. Very light cultivation with a hoe may be used to remove weeds. Organic mulches such as grass clippings, wood chips, straw/hay or compost can be applied 4 to 6 inches thick to suppress weeds.
Several herbicides are labelled for weed control in asparagus. Glyphosate (Round-up) can be used as a broadcast application to control winter annual and biennial weeds early in the spring before the spears emerge and after the last harvest. Cover crops such as rye or wheat may be spring-seeded in row middles to suppress weeds.
Selecting a site with good drainage and optimal pH will prevent many asparagus diseases. Crown rot, a potentially devastating disease, is caused by over harvesting, growing in acidic and waterlogged soils, and excessive pest pressure. Cercospora needle blight is often observed as reddish brown, elliptical lesions on the ferns. These lesions are followed by death of the foliage.
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 (two weeks) the second year after planting crowns (three 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 five to eight weeks. Each year, during the first several years of production, yields will increase if the planting is managed properly. Average yields 2.5kg per 100 square feet.
Asparagus spears are best harvested by cutting them off with a knife near ground level. Most people prefer to snap the asparagus spears when they reach 7 to 9 inches in length in cool weather (less than 70 degrees F), and the spear tip is tight or 5 to 7 inches in warmer weather (more than 70 degrees). Cutting will break the spear cleanly at a tender point. To preserve freshness, harvest during the moring or evening. Expect to harvest every one to three days as 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 short shelf life and should be immersed in cold water after harvest and immediately refrigerated (36 degrees F) to maintain quality.
After harvest, the asparagus planting should be fertilized with composted manure to stimulate summer and autumn fern growth. Herbicides can be applied after harvest to control any weed growth. Frost will desiccate the ferns, and they can then be cut in late autumn or early winter. Do not mow ferns in early autumn while they are still green because this will reduce the following spring harvest. We mulch the crowns to protect them from low-temperature injury. The mulch can be raked to the row middles the following spring (early April), and spears will emerge for another harvest season.
Holdens Country Store is a company registered in England and Wales with company number 6040180