Statesman gardening columnist Margaret Lauterbach is taking some time off. She’ll be writing again in January. But she’s checking her email, so if you have questions, email her at firstname.lastname@example.org. Meantime, we’re repeating some of her most popular advice.
Do you grow your own asparagus? Once planted right and well-tended, those crowns (roots) will continue to produce for 20 years or more. It's a perennial plant you'll find is very much worthwhile, producing spears from early spring to July. Since the harvest doesn't occur all at once, it is usually commercially hand-harvested, adding to the consumer's cost.
Where you grow asparagus is extremely important. Select a well-drained site that receives seven to eight hours of sun exposure each day and receives normal rain. Years ago I mistakenly planted a bed next to a western fence that blocked slanting rain from the west, our most common direction of precipitation.
Your asparagus bed should be separate, at least to some extent, from your annually tilled vegetable garden, but at a location you can get water to when needed. You won't need to alter soil at all, since our soil is so alkaline. Asparagus grows best in pH soil of 7.0 to 7.5. How many roots (crowns) will you need? It depends on your family, but estimates for a family of four range from 10 to 50.
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If you grow from seed, you'll have to wait years for harvest. You'll get a few usable spears in three years, and won't get a good harvest for four years after planting. Buy roots (crowns) that are at least 1 year old; 2- or 3-year-old crowns will yield faster, but they're more prone to transplant shock than 1-year-old roots. The older roots will necessitate digging a larger trench for them because the roots should stretch out when set into the trench. Buy rust-resistant and Fusarium-resistant varieties, and if you prefer, all-male varieties. The all-male asparagus doesn't set seed, so you won't have to pull out asparagus seedlings when weeding.
Dig a trench about 15 inches deep by about the same width, and put a 3-inch layer of well-rotted manure in the bottom. After that's tamped down, cover it with a 4-inch layer of compost or very good loam. Make sure your manure and compost have not been contaminated by one of the persistent herbicides. Build mounds of compost or loam in the trench and spread roots out over the mounds, taking care not to crowd or crimp the roots. Space them about 14-18 inches apart. Cover roots with about 2 inches of good garden soil to start with. As new spears grow, you may add more soil around them, but most folks don't completely fill in the trench until the roots' third year in situ. Don't get soil on the ferny spear, and never cover the growing tip.
Be diligent about keeping this area weed-free, for asparagus doesn't thrive among weeds. Do not break off the ferny stalks that rise from those roots, for they're feeding the roots. Keep the area weed-free, using mulch such as sawdust, shredded leaves or weed seed-free straw if you can find it. Weeds that do appear should be carefully hoed out or pulled. Packs of all-male plants often contain some female plants, and if so, you'll see seeds set on the ferns. Pull those off, or if you miss one or two, and seedlings pop up, pull them out immediately. If they're still there in a year, you can't distinguish them from your original planting.
The row should be heavily watered every two weeks, and fertilized with something approximating 5-10-5 or 10-10-10 (about one-third cup per crown) or better yet, herbicide-free rotted manure and compost in fall or after final harvest for the season. Some people feed asparagus in March, too, but I wouldn't use the manure that close to harvest.
When you do begin to harvest, break spears instead of cutting them, for a knife may spread disease. Harvest only spears that are as thick as an adult finger. A friend who lived on the first bench and received irrigation water said her asparagus spears were nearly 2 inches in diameter. My late friend Moira Ryan, author and teacher of organic gardening in New Zealand, suggested an asparagus grower ought to leave one sturdy spear per crown to grow and overwinter. Those tall ferny spears feed the roots, and leaving them intact over winter helps trap snow for root moisture. All ferny growths should be removed in early spring.
Europeans prefer white or blanched asparagus. Some blanch spears by hilling the soil, but it's easier to blanch it by covering with metal or dark-colored opaque buckets. Blanching makes spears tender, but I think less nutritious.
Asparagus does have some insect enemies, namely the asparagus beetle and slugs. There is also a spotted asparagus beetle, but its damage is minor compared to the other foes.