BLUE SPRINGS, Mo. - Asparagus is a dependable perennial vegetable, often lasting in the garden for more than 15 years. Asparagus is an excellent source of folic acid and a good source of vitamin C, potassium, B vitamins, copper, vitamin A, iron, phosphorus and zinc. To successfully grow asparagus, it is important to select both a good permanent site and a cultivated variety suitable to the area, said Lala A. Kumar, University of Missouri Extension horticulture specialist.

Asparagus is a dioecious plant, meaning male and female plants are separate. Usually the distribution of male and female plants is about equal. Male plants produce 25 percent to 40 percent more spears, but female plants produce larger spears. Female plants also produce seeds that can become weeds in the garden. Plant breeders have developed all-male varieties of asparagus that out-yield the old mixed male and female varieties.

"The most widely recommended all-male variety for our area is Jersey Knight, which is well-adapted to the heavy clay soil," said Kumar. Other recommended all-male varieties are Jersey Deluxe, Jersey Giant, Jersey King, Jersey Prince, Jersey Supreme and Jersey Gem. All these varieties are resistant to the fungal diseases rust and fusarium wilt.

Asparagus grows best in fertile, well-drained soil high in organic matter in an open location that gets at least six hours of sunlight. Plant the asparagus at either the west or north side of the garden in a permanent bed so it will not shade the other vegetables and will not be disturbed when the garden is tilled. The pH requirement for asparagus is 6.5 -7.5, so soil testing is recommended to determine liming, phosphorus and potassium needs.

The best time for planting asparagus seed or crown is mid-April to early May. Soak seeds for 48 hours at 85 to 90 degrees before sowing and plant with row spacing of 24 inches and within-row spacing of 6 inches. (Transplant crown grown from seed to a permanent location the following spring.) Or you can purchase 1-year-old, disease-free crowns from a reputable source and plant them directly to a permanent site with row spacing of 5 feet and within-row spacing of 1.5 feet. Dig the furrow no deeper than 4 to 6 inches.

"Do not harvest the asparagus during the planting year," said Kumar. "The second year after planting, harvest for six weeks to seven weeks if growth is strong. Thereafter, you can take a full harvest-usually about eight or nine weeks." Over-harvesting reduces the next season's yield. Immediately after harvest, apply 2 pounds of 5-10-10 fertilizer per 100 square feet of asparagus bed, or spread a layer of well-decomposed animal manure or compost.

In a small garden, control weeds through shallow cultivation by hoeing. Asparagus is drought-tolerant so no supplemental irrigation is needed. Harvest when tender spears are about 4- to 6-inches long. Snapping spears instead of cutting them helps limit the spread of fusarium wilt. For the best quality, harvest early in the morning while spears are cool.

To learn more, see MU Extension guide "Growing Asparagus in Missouri" (G6405).