White asparagus is a spring vegetable. It is a flowering perennial plant of the lily family and can survive for 20 years or more. White asparagus is mainly cultivated in the Netherlands, Spain, France, Poland, Belgium, Germany, Austria, Turkey, Italy, and Switzerland. White asparagus is locally known as “white gold” or “edible ivory” asparagus, also referred to as “the royal vegetable”. It is used as vegetable and medicine. Nutritional value per 100 g Asparagus is:
|Total Fat||0.12 g|
|Dietary Fiber||2.1 g|
|Pantothenic acid||0.274 mg|
|Vitamin C||5.6 mg|
|Vitamin E||1.13 mg|
|Vitamin K||41.6 µg|
White Asparagus Types:
The most common varieties of white asparagus are likely to from European breeders. ‘Mary Washington’ and ‘Jersey Knight’ are two good varieties of white asparagus. There are some hybrid varieties of asparagus which have higher yielding and greater photosynthate accumulation capability.
Asparagus is cultivated in subtropical and sub-temperate agro-climatic regions.
Organic-rich deep sandy soil is best for asparagus cultivation. The soil must be free from rocks and perennial weeds. The soil must have a high level of organic matter. Neutral to the slightly acidic soil is suitable for asparagus cultivation. 6.5 to 7.5 is the ideal pH level for asparagus cultivation. You can add lime to make the soil slightly acidic.
Saplings are normally produced from “Crowns” (1-year-old plants). To produce field crowns sow seeds in early spring and lift the crowns before new growth emerges. After lifting wash the crowns and store them according to their size. Store them at 5-7° C. Plant these crowns in the field in late fall when there is no risk of frost. You can also use imported saplings. Holland produces the best saplings of asparagus.
Land Preparation and Planting:
Deep plowing about 20 to 25 cm followed by 2 to 3 harrowing after few days should be carried out. Apply 10 to 20 tons per acre of clean manure. Dig trenches of two feet wide at the top and taper to a point at the bottom. Implant the saplings in late fall in the trenches about of 10 to 12 inches deep. You can implant the saplings by hand or can use a ditcher device. Implant the crowns in the same direction as the rows to control spreading of crowns. Place the crowns at the furrow bottom on a small mound of soil and spread the roots over the mound surface. Cover and firm the roots by patting down few inches of soil.
The distance between the two crowns should be 10 to 12 inches. There should be space between two rows for creating and maintain hills. There should be 6 feet vacant space between two rows. Provide irrigation immediately after planting. Approximately 6,000 crowns may be planted in the one-acre land. Small ferns emerge from the crowns and expand. These ferns gradually fill the trenches. Level the soil throughout the planting at the end of the first season.
Hilling is an important part of asparagus cultivation. Arrange hills in the second year of growth of plants and maintain it annually throughout the life of the plants. Make hills of 14 inches high above the crown surface and. Align the center of the hill perfectly so that spreading spears appear on the hill crown.
Provide 2 to 3 irrigation in winter and 2 irrigation per month in summer. Make sure that the drainage system is well enough to prevent waterlogging in the rainy season.
Don’t use any chemical fertilizer for asparagus cultivation especially when you cultivating it for medicinal purpose. Each year, when the first spears emerge, apply garden compost or organic decomposed organic manure or green manure.
Always keep the land free from weeds. Two to three weedings are needed in the rainy season and one in 2 to 3 months is needed in other seasons. To prevent the damage of shallow root, carry out weeding by hand rather than the hoe.
Common diseases of White Asparagus:
It is a foliar disease. At the end of fern season, cut and burn the ferns. Proper irrigation reduces the risk of rust attack.
Purple spots are sunken, purple, oval-shaped lesions. They develop on asparagus spears and may affect most of the plants of the land. To prevent purple spot burn crop debris in late fall or winter. You can get help from the TOM-CAST disease forecaster to predict when to apply fungicides.
Fusarium Crown, Root, and Lower Stem Rot:
When these attack russet-colored lesions appear on roots, lower stems and/or crowns. They mainly caused during the time of drought. Provide proper irrigation during times of drought. Fumigate fields before planting.
Phytophthora Crown, Root and Spear Rot:
This infection caused more likely in wet soil. Spear rot turns into soft, water-soaked lesions and shriveling occurs slightly above or below the soil line. Avoid low-lying or poorly drained field for asparagus cultivation. Provide fungicides according to the suggestion of MSU Extension Bulletin E312.
Common Pests of White Asparagus:
It belongs to the Scarabaeidae Family. Grubs of this pest are creamy-white, C shaped and eat the roots of grasses. The adults are 1 to 3 of an inch long. Use pheromone traps to detect the flight. Scan the top of the asparagus fern and scout the beetles.
It belongs to the Agromyzidae family. Small black fly is less than 0.2 inches in length. To prevent this pest remove field debris over the winter. You can use degree-day model on MSU’s Enviro-weather website. Uproot the volunteer asparagus plants around fields.
Common Asparagus Beetle:
It is from Chrysomelidae family. Adults are 0.25 inches long and have few black spots on a red thorax. Scout the adults and larvae in the afternoon. Apply insecticide during the harvesting season.
In the northern hemisphere, harvesting starts in April. Only collect those spears which are 9 inches long. Collect the emerging spears by hand just as the spear cracks the soil surface. Gently remove the soil by hand. Remove down the soil by hand to the base of the hill where the spear is cut. During harvesting keep the harvested spears in a covered box where there is no light. If you keep them in the light they will turn pink. In the first season, you can collect spears for 10 to 15 days. For mature plants the harvesting time increase to 6 to 8 weeks.
Post-harvesting Care and storage:
Immediately after harvesting Submerge the collected spears at 2° to 4°C cold water for 5 hours. Then grade them according to their shape and size. Store them in 1°C temperature at 85% to 90% relative humidity.
Yield varies due to different environmental condition and soil types. Normally the average yields are between 8000-14000 kg/hectare.
White asparagus is a perennial plant and mainly cultivated in European countries but nowadays it also cultivated in some Asian countries. There is a great demand for asparagus as vegetable and raw materials of medicine. You can cultivate it in your garden. Commercial cultivation of asparagus is a very profitable business.