Eugene Weekly : Gardening : 10.14.10


Backyard Asparagus 
A good bed will produce for 15 years
By Rachel Foster

Europeans have a preference for fat, white asparagus spears, usually canned. I prefer mine green, thin and fresh. White asparagus is not a special kind. It has been blanched by piling soil over the emerging shoots. Light turns the spears green. Diameter, in turn, has less to do with variety than with the age of the patch and when the spears are harvested. Early in the season, spears are fatter. I’ve heard that the fattest spears are produced only for a plant’s first few years of productivity, from primary buds. A well prepared bed can be productive for 15 years.  

I like to eat asparagus, but until I visited Tom and Victoria Schneider’s garden a few years ago, I had not thought very much about how to grow it. It was the end of March, and the Schneiders’ 5-year-old asparagus bed was putting up big, fat spears. Tom Schneider picks all the shoots until they diminish to the thickness of a pencil. That’s almost two months of a delectable gourmet treat, which no doubt makes the initial work and wait worthwhile. 

Asparagus is usually planted in the form of dormant crowns, available at garden centers in early spring. But the best time to prepare a new asparagus bed is now, when soils are at their most workable. Our climate is not the best for growing asparagus, since wet winter soil can cause the roots to rot. The plants prefer deep, rich soils that drain well in winter. The surest way to achieve that is to build a raised bed. Steve Solomon, creator of Territorial Seed Co. and author of Growing Vegetables West of the Cascades, suggests it should be four feet high and wide, but many gardeners grow asparagus successfully in beds lower and narrower than that. 

Books recommend that you plant asparagus on the west or north side of the garden so that it will not shade other crops. Tom Schneider‘s bed is up against a south facing fence. “One of the things I like about that location,” he says, “is that it catches the early spring sun and warmth. Also, after harvesting is over and the ferns are growing, I can rope them up against the fence to keep them out of the path and out of the more productive areas of the garden.”

Start by building a raised bed, with or without boards, of purchased sandy loam or your own good, weed-free soil. Work in as deeply as you can an inch or two of compost, a pound of dolomite lime and a pound of rock phosphate or bonemeal per 10 feet of row. Cover the new bed with more compost or leaves, and perhaps with a tarpaulin to keep it dry over the winter. Since an asparagus bed is a long-term proposition, it should start out free of all perennial weeds and be weeded religiously thereafter.

Recommended planting times vary from February  to April, taking into account the condition of the soil. There is no advantage to planting the crowns early in cold, wet soil, because they won’t grow until the soil warms, and they are more susceptible to rot if exposed to cold, wet soil too long. In spring, work in a cup and a half of complete organic fertilizer per 10 feet of row. Dig a wide trench no deeper than 5 or 6 inches. (Deeper planting was suggested at one time, but research has shown that the deeper planting reduces the yield.) Space the crowns about a foot apart in the row and spread out the roots. Backfill the trench part way; add more soil as the shoots extend. 

The crowns you buy will be a couple of years old, and it will be a couple more before you should harvest anything. Let all the shoots develop into tall, feathery “ferns.” By the third year after planting, the shoots should be thicker and more numerous, and you can harvest them for about three weeks, snapping off the shoots at soil level. 

In a wet climate like ours, Schneider and others suggest that the top growth should not be allowed to winter over. Cut down the ferns in November or December and mulch the row heavily with manure or compost. Asparagus will not do well if the pH is less than 6.0, so every few years you will need to add another pound of lime per 10 feet of row, in the fall. After the spring harvest, fertilize with 1-2 cups of organic fertilizer per 10 row feet. Asparagus is a heavy feeder! 

Rachel Foster of Eugene is a writer and garden consultant. She can be reached at