Go with crowns. You can start asparagus by sowing seed, but most gardeners start with crowns (the dormant roots). Crowns will yield the first harvest a year sooner than seed (two years rather than three). And seeds produce female as well as male plants. Female plants produce less than males for they use much of their energy to set seeds and grow foliage, while male plants put all their energy into making spears. (Red berries after flowering means a female plant.) Experts recommend identifying the female plants early on and removing them. With crowns, you can get male plants only.
Start with a dozen. Crowns look a bit like tangled spaghetti. Buy only crowns that look healthy—avoid those that look rotted or dried-out, brown or shriveled. About one dozen crowns will produce enough to feed one adult in a season; plant as many as 20 crowns per adult if you plan to freeze or can spears.
'Martha Washington' and 'Mary Washington' are the old standbys, but newer hybrids from Rutgers University and the University of California give higher yields, are more disease resistant, and can be harvested the second spring after planting.
Northern gardeners can try the Jersey hybrids, all-male varieties developed at Rutgers University. 'Jersey Knight' is longer-lived than some of the other Jersey hybrids and is tolerant of fusarium and resistant to rust. 'Jersey Giant' is more productive than 'Jersey Knight' in cold areas, such as Michigan, and is adaptable to a variety of growing conditions, while retaining good disease resistance.
The University of California (UC) hybrids are suitable for warmer, dryer climates. They grow enthusiastically from the southwest up to Washington State. These hybrids are not all male, however. The tips of 'UC72' stay tight in warm climates; 'UC157' spears are tinged with purple, and has higher yields than 'UC72.'
Site, Soil and Planting
Think permanent. Choose the site carefully and your asparagus will grow there for years to come. Allow both vertical and horizontal space for the ferny leaves that asparagus grows after it's finished producing spears. The ferns can reach up to 5 feet tall, so plant where the foliage won't shade other plants that need sun.
Full or partial sun. Asparagus prefers full sun but—rare for the vegetable kingdom—it can take some shade.
No weeds. Asparagus doesn't compete well with weeds, so remove them all before you plant, mulch the bed well (with compost, rotted leaves or straw) and pull any weed that peeks through the mulch.
Check the soil. Asparagus enters into a long-term relationship with your soil, so make sure conditions are ideal before that first crown is planted. A soil test is the place to start. Asparagus is a heavy feeder, so the soil should be rich in organic matter to help make all the nutrients available to the roots. Compost is the best source of organic matter for your asparagus bed.
Good drainage. The soil must be well-drained so that it stays evenly moist, but never soggy. Poor drainage will cause the roots to rot. Sandy loam is best, with a pH of 6.5-7.5.
How to Plant Asparagus
Carve a trench. As soon as the soil can be worked in spring, dig a trench about 12 inches deep and 12 to 18 inches wide. Leave 3 to 4 feet between each trench, if you have room for more than one.
Backfill with compost and soil. Put 4 inches of compost or well-rotted manure into the trench. Shovel in 2 inches of soil, and mix it with the compost. Then add bonemeal: 1 pound for every 20 square feet. The phosphorus in bonemeal strengthens the developing roots. Shovel in 1 more inch of soil and mix again. The trench should now be about 6 inches deep.
Mound the ground. Set the crowns about 18 inches apart in the trench. Mound the soil beneath each crown (as you would with a rose bush) and fan the roots evenly over the mounded soil. When all the crowns are in the trench, cover them with 2 to 3 inches of compost or rotted manure. Gently firm the soil, and water the trench. Leave the remaining soil where it is; as the stems grow you'll use it to fill around them.
Add more soil. When you see the top start to grow in 2 to 3 weeks, shovel about an inch of the reserved soil around the shoots. Keep adding soil as the shoots grow, about every week or so, until the trench is refilled.
Water and wait. Be sure your asparagus doesn't dry out through its first spring and summer. Water it when Mother Nature doesn't. Don't harvest any of the spears the first year. Think of asparagus like marriage: a long-term commitment that, with care, only gets better with time.
Maintain the mulch. Layer a half-inch of compost on the soil in spring and again in fall. Remember to keep the bed weed-free, but do not cultivate the soil because it might disturb the roots. A layer of shredded leaves or straw will help conserve moisture and keep weeds down.
Leave the ferns in fall. Once the stalks stop coming up, the tall, lacy ferns appear. They might look familiar; asparagus fern is a common houseplant, and a cousin of the vegetable. Don't cut the ferns down; they're collecting energy for next year's stalk growth. Let the foliage yellow and die back in the fall to protect the bed during the winter.
Remove them in spring. Diseases and the eggs of destructive insects can overwinter in the foliage, so remove it in the spring before new growth appears.
Take two. The year after you plant, you can harvest a few stalks. Stop after two weeks. Gradually harvest more in succeeding years—by the fifth year you should be able to enjoy 8 to 10 weeks of continued asparagus bliss.
Cut on the line. Choose spears that are 6 to 8 inches tall and a half inch thick or more, with tightly closed tips. Cut close to the soil line, never below it.
Keep them a week. Store asparagus spears in the refrigerator. They stay fresh for about a week if placed standing up, with the cut ends in an inch or two of water.
Asparagus Pests and Diseases
New varieties vs. fungus. Asparagus spears in situ look almost comically naked and vulnerable, so you might be surprised to know that they're not troubled much by pests or diseases. Rust and fusarium wilt, two fungal diseases, are the two that have been most troublesome to asparagus growers. Most new varieties are resistant to both, and that's especially good news because the only thing to be done once either strikes is to start again with new crowns in a new location. Rust is caused by too much moisture— its orange, yellow or white blister-like spots can appear anywhere on the plant. Fusarium stunts spears and can turn them brown and inedible.
Beat the beetles. Both larval and adult asparagus beetles feed on spears, creating holes and causing the spear to curl. Handpicking is usually sufficient to control them. For more serious infestations, protect the spears with row covers from early spring until the end of the harvest. The beetles overwinter in old foliage; clear it away before stalks appear.
Asparagus, as many Europeans know and love it, isn't green—it's white. This is not a different variety, but the result of blanching, or mounding soil over the emerging stalks, depriving them of sunlight and the ability to make chlorophyll. White asparagus stalks are thicker, and many people believe more tender, than their green brethren. Ruth Stout, the feisty evangelist of "no-work" gardening, bluntly disputed the claim of white asparagus' superiority. "Let's just skip the fantastic idea of making mounds over the asparagus in order to bleach it," she wrote in How to Grow Fruits and Vegetables by the Organic Method (Rodale Press, 1961). "That's for the birds—and some Europeans, who were brought up on white asparagus and haven't seen the light. Nowadays, health-conscious people urge us to eat green-colored foods, the greener the better. Assuming that this is a beneficial thing to do, isn't it wonderful that for once the thing that's good for us is less work than that which isn't so good?"