How to Grow Asparagus

comments (0) July 31st, 2008     

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by Karen Pendleton
February 1997
from issue #7

My family didn’t grow asparagus when I was a child. We found it. My dad had a sharp eye for the tender green spears that grew wild along roadsides near our home in Piqua, a wisp of a town in southeastern Kansas. He could spot even a single spear when he took the family on Sunday afternoon drives. He would stop our Plymouth Fury and gather the crop.

I developed a passion for asparagus, too. Only now, though I fondly remember those asparagus hunts, I find it much easier to simply step out the back door of my house and snap a few delicious spears from the bed in our garden. When I first planted asparagus, I was a little intimidated by all the folks who said it was hard to grow. Starting a bed does take more work for asparagus than for many other vegetables. But after 15 years, and expanding to 20 acres for commercial production on our farm in Lawrence, I know asparagus is one of the tastiest, easiest vegetables you can grow.

Long lives the bed of crowns

	Asparagus needs a big start • Choose a sunny part of the garden with good drainage. • Dig a trench and check the pH, which should be 6.5 to 7.5. • Plant the crowns about 8 in. deep and 15 in. apart. • Cover initially with 2 in. of dirt, and gradually fill the trench as the spears emerge.

Asparagus is a perennial crop, its long green fingers coming up year after year. So when you make your bed, do it carefully. Your asparagus may be growing in it for 20 years or more. A sunny, well-drained part of the garden will yield the best crop. Asparagus, a good candidate for raised beds, should be planted in soil with a pH of 6.5 to 7.5. I’m lucky my patch was once a cattle feed lot, so I rarely add fertilizer, but people with poor soil may want to fertilize lightly.

Consider weather in selecting a variety. New hybrid asparagus varieties abound. The old standard ‘Mary Washington’ has long been good, but research and breeding have produced some fine alternatives. California varieties tolerate the heat better and keep a nice, tight tip, even above 80˚F. I prefer ‘U.C. 157’, a University of California plant, because we can get many hot days in late spring. New Jersey breeders are offering “all male” plants, which yield more than female plants since they don’t use energy to produce flowers and seeds. In my garden, the ‘Jersey Giant’ tips tend to loosen if the temperature gets above 80˚F, resulting in many undesirable spears.

	Most people start their asparagus from crowns, not seeds. The root masses should be fresh and firm. Dry sections of the roots can be pruned before planting.
	Deeper plantings tend to produce thicker but fewer spears.

Seeds vs. crowns. You can start your asparagus with seeds, but they take six weeks to germinate and add another year of growing time before the first harvest. So most people start with the asparagus crown, the root mass and buds. When buying crowns, look for fresh, firm-fleshed roots. If they are shriveled or feel like paper, they may be old and won’t produce well, if at all.

Plant crowns early. Crowns should be planted while they are dormant. That can be as early as late winter. They should be planted when the ground is workable, between frosts. As long as the crowns are covered with about 2 in. of soil, they won’t suffer in hard freezes. They can be planted as late as mid-spring, if plump, healthy roots are still available.

A few crowns can be planted merely by digging individual holes for each plant. If you want to plant more, dig a trench. If the soil is heavy clay, the trench should be deep enough to accommodate a layer of compost or other organic material under the crowns. The optimum depth to plant crowns is 6 in. to 8 in. Shallower plantings yield many spindly spears, while those planted deeper produce fewer spears of larger diameter. Place the crowns in the furrow, and cover initially with 2 in. to 3 in. of soil. Keep adding to the trench as the spears emerge. By season’s end, it should be filled. You can fill the trench completely at planting time, but by doing it gradually, you move the dirt and control the weeds.

Asparagus stays healthy with breathing room. Space the asparagus crowns so you get as many plants as possible in a small area, but still allow for good air circulation to protect against disease. I plant my crowns 15 in. to 18 in. apart in rows 5 ft. apart. Figure on 10 plants for each person in the family who loves asparagus. This ought to enable you to harvest enough at one time for a meal.

Modest care pays dividends
When you’ve established your asparagus bed, the hard part is finished. Still, you must follow good culture practices to assure successful crops.

	Related article: • Quick and Light, Asparagus Hits the Spot • Using Asparagus in Season and Beyond Asparagus recipes: • Fresh Asparagus Soup • Pickled Asparagus • Stir-Fried Shrimp and Asparagus

Weeds must be controlled. This can be done mechanically with a hoe, cultivator, or rotary tiller. To avoid damaging the asparagus roots, don’t till deeper than 2 in.  Weed-blocking fabric and mulch will also help. Many gardeners use coarse salt to keep the weeds out. Asparagus tolerates salt, while most other plants don’t.

Except under almost desert conditions, asparagus, with its extensive root system, doesn’t need irrigation. I’ve learned that asparagus drowns much more quickly than it dies of thirst.

Asparagus does, however, need to be protected from pests. The asparagus beetle can nibble on spears and lay dark eggs along the surface. Unless a great amount of asparagus is grown in your area, this is mostly just a nuisance. Scrape off the eggs with your fingernail.

Fungal diseases like asparagus rust, which first appears as small reddish-brown spots on stems, can be treated with fungicides. The new hybrid varieties, however, resist disease.

A royal harvest worth the wait
It takes time to grow accustomed to the asparagus harvest cycle. Although the harvest is about six weeks long, it’s over just as many people start thinking about local summer produce. The asparagus harvest in Kansas usually starts about the middle of April and runs until the first of June. Spear growth depends on temperature. If it’s cool, the asparagus may need to be harvested every three days; if hot, every day.

Older varieties had to grow for three seasons before they could be harvested. With the increased vigor of the new hybrid varieties, gardeners can harvest for about two weeks during the first season, a year after planting. A light harvest seems to stimulate the plant to produce more spears. A full six-week harvest season may follow in year two, provided the average size of the spears is larger than a pencil.

	Snapping off the spear by hand is easyl and it protects the plant. You can use a knife, but be careful not to damage developing stems.
	At the end of the harvest, allow the asparagus to form ferns. They help transfer eergy to the roots for good spear development the next season.

Harvesting is a snap. Spears should be harvested by hand when they are 6 in. to 8 in. tall and the tips are still tight.

I recommend snapping asparagus off at soil level. This severs the spear at the junction between the green tender tissue above the ground and the white woody tissue below. All of the stalk you get is edible, and you won’t injure spears that have not yet emerged. You can use a knife to cut the spears just below the surface, but be careful not to damage the developing spears and the crown.

If you plan to store the asparagus for several days, leave some of the white, woody base. It restricts water loss and helps preserve the upper spear.

Fern formation is critical to next year’s growth. The asparagus will keep growing throughout the summer. But difficult as it may be, you must stop harvesting so some of the spears can go to fern, the stage when the tips turn feathery.

Ferns should not be removed from asparagus plants until after several killing freezes. I often recommend leaving the tops for winter mulch. This mulch can catch snow and protect the plants from severe cold, while adding moisture. More important, however, the ferns also transfer carbohydrates and energy to the roots by photosynthesis. This process is crucial to the development of spears for the next year's harvest.

Sources for asparagus crowns The following sources grow and ship their own asparagus crowns, but all may not carry the same varieties. Daisy Farms 28355 M-152 Dowagiac, MI  49047 269-782-6321 Simmons Plant Farm 11542 N. Hwy. 71 Mountainburg, AK 72946 479-369-2345 Jersey Asparagus Farms, Inc. 105 Porchtown Rd. Pittsgrove, NJ 08318 856-358-2548

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