Asparagus Growing and Care Calendar

By Steve Albert On March 16, 2012 In Gardening Tips, Guides

Asparagus is among the earliest and tastiest crops each year. Perennial asparagus beds can produce spears for decades and decades with proper care through the years.
Plant asparagus where there is plenty of sun in the spring and the soil is rich in organic matter and well drained. As a guide, you will need about 20 to 40 crowns for each person; 20 for the spring harvest and more for a second or third harvest later in the season.
Keeping the asparagus patch productive will require a few simple tasks each season.
Here is a season-by-season guide for asparagus growing and care:
Spring. Asparagus spears will be ready for harvest shortly after the soil temperature reaches 50°F in early spring—that’s when spears will begin to emerge. Two week before spears begin breaking through the soil, pull the winter mulch back and cultivate the asparagus patch lightly loosening the soil and uprooting weeds.
Begin the harvest when spears are 6 to 8 inches long; that’s when they are most tender. Don’t let spears grow taller; they will become tough. Harvest spears daily during the harvest period; hand snap each spear off just below the soil surface.
Harvest will last 2 to 10 weeks depending upon the age of the plants. The first harvest year pick spears for 2 weeks; this will allow roots to become established and grow strong. Each year after, increase the spear harvest by a week.
Once spears have started to grow tall, weed the growing bed once more then place a 4 to 6 inch layer of straw or hay or dried grass around plants for the remainder of the harvest and growing season. Mulching after spears have emerged will keep weeds down and preserve soil moisture through the warm time of the year. Weeds that grow up through the mulch can be easily pulled by hand. An alternative is to sow annual rye grass around asparagus plants in spring. Rye grass will crowd out small weeds and will die off in winter.
Late spring. Plant for future asparagus harvests in late spring. Sow asparagus seed 1½ inches deep and 2 inches apart in loose, well-drained soil. Sow seed when the soil temperature is between 70 and 75°F. Seeds should emerge in 10 to 20 days. Keep the soil moist and control weeds. Later, thin plants to 12 inches apart.
Transplant asparagus crowns (one-year-old rhizomes) in spring about the same time you transplant out tomato plants. Set crowns at the bottom of a trench 10 to 12 inches deep and cover with 2 to 3 inches of soil. Set crowns 12 inches apart. As plants begin to grow cover the new growth with 2 inches of soil every few weeks until the trench is filled. When spears shoot up the first year, let them leaf out and grow on.
After harvest in spring, feed each plant an organic fertilizer to support top growth through the summer; summer growth will determine how good the following year’s spears will be. Aged compost and well-rotted manure will feed asparagus beds. (Add nutrients in spring before spears emerge and again after the last harvest.) A rich asparagus fertilizer is three parts greensand, two parts cottonseed meal, one part dried blood, and one part bone meal applied at the rate of 2 pounds per 50 square feet of bed.
During the warm season, keep weeds down with a thick layer of straw, hay, or dried grass clippings—fresh grass clippings contain too much moisture to use as a mulch without first drying; they can become slimy and moldy if applied freshly cut. Weeds will compete with asparagus plants for nutrients and diminish both yield and spear size.
Summer. After harvest, let the plant’s fernlike foliage grow tall. Summer growth allows asparagus roots to grow large and store energy for the following year’s spears. Stakes and string will keep plants upright. In breezy areas, plant rows parallel to the prevailing wind so that plants can support each other. Crowns grow upwards about 1 inch each year, so spreading compost across the planting bed or along rows in summer will both feed plants and raise the soil surface.
To get a second or more harvests each year, plant twice the number of plants or more needed for each person (40 rather than 20) then harvest only half of the bed in spring and let the other half grow on. In early summer, cut down the top growth in the half of the bed that was not harvested. This section will send up new spears in a few weeks that can be cut in late summer or early fall for a second harvest. If the growing bed is large enough, you can divide the bed into sections and use this method for a new 2 month harvest every 8 weeks, multiple asparagus harvests each year.
Late Fall and Winter. In mild winter regions, cut down ferny top growth after it has turned brown in late fall or winter. (Even in autumn, asparagus tops may look dead but are still storing energy for spear production the next spring.) In cold winter regions, don’t cut back top growth; let it provide extra protection for roots from freezing temperatures.
(You can allow asparagus berries to mature and drop each fall. In spring, thin out new plants started from dropped berries; allow some new plants to establish and replace older plants.)
Where you cut back top growth, mound 3 or 4 inches of soil over crowns or add 3 to 4 inches of aged manure and compost across the bed to protect roots from cold temperatures. An alternative is to mulch the bed with 8 inches of loose straw or hay and add phosphorus and potassium rich cottonseed meal and wood ashes across the mulch. Deep mulching is important in cold regions to protect asparagus from tip-kill in spring and feeding is important for future spear production. A decline in spears is commonly the result of lack of nutrients.
Adding 4 to 6 inches of aged compost over planting beds and asparagus crowns each year effectively increases the depth of the crowns which in turn increases spear size and tenderness the following spring. When spears become spindly, crowns may have grown too close together and older plants should be thinned out.
Leave winter mulch in place until the danger of a freeze has passed in late winter or early spring, then pull the mulch back and ready the bed for the spring harvest.

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Asparagus Growing Guide

Rich in B vitamins, vitamin C, calcium, and iron, asparagus is one of the first crops of spring harvest.

Asparagus is a perennial vegetable grown for its delicious young shoots. Rich in B vitamins, vitamin C, calcium, and iron, asparagus is one of the first crops of spring harvest. Fresh-picked spears are far more tender and tasty than store-bought ones.
Asparagus thrives in any area having winter ground freezes or dry seasons. The mild, wet regions of Florida and the Gulf Coast are about the only places where it’s difficult to grow.
Planting
Select and prepare your asparagus bed with care; this crop will occupy the same spot for 20 years or more. It can tolerate some shade, but full sun produces more vigorous plants and helps minimize disease. Asparagus does best in lighter soils that warm up quickly in spring and drain well; standing water will quickly rot the roots. Prepare a planting bed about 4 feet wide by removing all perennial weeds and roots and digging in plenty of aged manure or compost.
Asparagus plants are monoecious—each individual plant is either male or female. Some varieties of asparagus, such as ‘Jersey Knight’ and ‘Jersey Giant’ produce all male or primarily male plants, so they’re more productive—male plants yield more harvestable shoots because they don’t have to invest energy in producing seeds. Choose an all-male variety if high yield is your primary goal. If you like to experiment, you may also want to grow an heirloom variety or a purple-stalked variety like ‘Purple Passion’. With an all-male variety, twenty-five plants are usually adequate for a household of four; plant double that amount for standard varieties. (Ardent asparagus lovers recommend tripling these quantities.)
Starting asparagus from 1-year-old crowns gives you a year’s head start over seed-grown plants. Two-year-old crowns are usually not a bargain. They tend to suffer more from transplant shock and won’t produce any faster than 1-year-old crowns. Buy crowns from a reputable nursery that sells fresh, firm, disease-free roots. Plant them immediately if possible; otherwise, wrap them in slightly damp sphagnum moss until you are ready to plant.
To plant asparagus crowns, dig trenches 12 inches wide and 6 inches deep (8 inches in sandy soil) down the center of the prepared bed. Soak the crowns in compost tea for 20 minutes before planting. Place the crowns in the trenches 1½ to 2 feet apart; top them with 2 to 3 inches of soil. Two weeks later, add another inch or two of soil. Continue adding soil periodically until the soil is slightly mounded above surface level to allow for settling.

Asparagus Growing Guidelines
Apply mulch to smother weeds, which compete with the young spears and reduce yields. Carefully remove any weeds that do appear. Water regularly during the first 2 years after planting. As asparagus matures, it crowds out most weeds and sends long, fleshy roots deep into the earth, so watering is less critical. Fertilize in spring and fall by top-dressing with liquid fertilizer (such as compost tea) or side-dressing with a balanced organic fertilizer.
Leave winter-killed foliage, along with straw or other light mulch, on the bed to provide winter protection. Remove and destroy the fernlike foliage before new growth appears in spring; it can harbor diseases and pest eggs.
If you want to grow white asparagus, which has a slightly milder flavor than green asparagus, blanch the spears by heaping up soil or mulch over the bed before they emerge.
Starting Asparagus from Seed
It takes patience to start your asparagus patch from seed, but there are advantages to gain from the extra wait. Seed-grown plants don't suffer from transplant trauma like nursery-grown roots, and you can buy a whole packet of seed for the same price you'll pay for one asparagus crown. Most seed-grown asparagus plants eventually out-produce those started from roots. Growing from seed also allows you to selectively discard female plants and plant an all-male bed, no matter what variety you choose to grow.
In the North, start seedlings indoors in late February or early March. Sow single seeds in newspaper pots, place the pots in a sunny window, and use bottom heat to maintain the temperature of the mix in the pots at 77°F. When the seeds sprout, lower the temperature to 60° to 70°F. Once the danger of frost is past, plant the seedlings (which should be about 1 foot tall) 2 to 3 inches deep in a nursery bed.
When tiny flowers appear, observe them with a magnifying glass. Female flowers have well-developed, three-lobed pistils; male blossoms are larger and longer than female flowers. Weed out all female plants. The following spring, transplant the males to the permanent bed.
Problems
Healthy asparagus foliage is necessary for good root and spear production. Asparagus beetles, which chew on spears in spring and attack summer foliage, are the most prevalent problem. The 1/4-inch-long, metallic blue-black pests have three white or yellow spots on their backs. They lay dark eggs along the leaves, which hatch into light gray or brown larvae with black heads and feet. Control by hand picking; spray or dust seriously infested plants with insecticidal soap. These methods also control the 12-spotted asparagus beetle, which is reddish brown with six black spots on each wing cover. Asparagus miner is another foliage-feeding pest; it makes zig-zag tunnels on the stalks. Destroy any infested ferns.
Avoid asparagus rust, which produces reddish brown spots on the stems and leaves, by planting resistant cultivars. Minimize damage from Fusarium wilt, which causes spears, leaves, and stems to be small with large lesions at or below the soil line, by purchasing disease-free roots and using good garden sanitation. Crown rot causes spears to turn brown near the soil line. Prevent crown rot by planting in raised beds, maintaining good drainage, and keeping soil pH above 6.0.
If your asparagus bed does become infected by disease organisms, your best option is to start a new bed in a distant part of the garden, using newly purchased or grown plants.
If young spears turn brown and become soft or withered, they may have been injured by frost. Cover spears with mulch or newspaper when freezing nights are predicted.
Harvesting
Don’t harvest any spears during the first 2 years that plants are in the permanent bed. They need to put all their energy into establishing deep roots. During the third season, pick the spears over a 4-week period, and by the fourth year, extend your harvest to 8 weeks. In early spring, harvest spears every third day or so; as the weather warms, you might have to pick twice a day to keep up with production. Cut asparagus spears with a sharp knife or snap off the spears at, or right below, ground level with your fingers.
This article is courtesy of Rodale's Ultimate Encyclopedia of Organic Gardening.