White Asparagus (cont)
By: Christopher O. Bird
When, How, and What to Plant
Early spring is the best time to plant asparagus in most regions, except if you live where winters are mild. In that case, plant in late fall. Start by amending the soil with compost. Asparagus prefers soil that is neutral to slightly acidic, so if necessary, add lime to correct acidity or sulfur to correct alkalinity. The plants come as crowns, which are clumps of roots. Nine crowns, planted 2 to 4 inches deep and about 15 to 16 inches apart, will fill a 4-foot-square bed in about three years. Both male and female plants produce edible spears, though all-male varieties are said to be more productive. (I haven't noticed much difference.)
'Mary Washington' and 'Jersey Knight' are good varieties, and plants are readily available from mail-order catalogs. 'Mary Washington' may be more rust-resistant. 'Jersey Giant' produces such large spears that the largest among them may be a little tough and stringy. Based on experience, I would avoid no-name bargains. They may be inferior strains being unloaded by a breeder.
Care and Harvesting of Asparagus Plants
Each year, when the first spears begin to emerge (around the first of May in my area), I apply a cheap, fast-release lawn fertilizer, such as 30-3-3, and water it in. This encourages good top growth for the harvest period. Then I put on the top. The bed won't receive rain, of course, while the top is on, but I seldom have to water, because the covered soil doesn't dry out much.
Surprisingly, air circulation isn't a problem, either. During my first harvest, I created some openings for ventilation. Not only did this turn out to be unnecessary, but it let in a little indirect light, which made the spears pale green instead of white.
Pests and Diseases
Japanese beetles are the main pests in my garden, so I put out a trap. The other common pest is asparagus beetle. Fortunately, though, in both cases, my harvest is over before the beetles begin theirs, and by that point they cause relatively little damage compared to the size of the plants. I have rarely had to apply a pesticide.
An occasional problem is rust, which shows up in a few wilted spears. A standard vegetable-garden fungicide seems to cure it (but maybe the problem would clear up on its own). After cutting off the infected spears, I drench the soil with the fungicide, trying to avoid getting any directly on the good spears that remain. (To be safe, I wash those spears thoroughly before cooking.)
When and How to Harvest
Be sure to harvest -- or at least peek under the top -- every two days or so throughout the cutting season. The spears grow fast in the dark, and if you go too long without checking, some will grow too tall and bend after reaching the plywood ceiling.
Many growers say it's best not to harvest any spears in the first two years. That's probably true, but raised beds like these are so efficient that it really doesn't hurt to harvest for two to four weeks the second year. After that, you can harvest for four to six weeks each spring, or until most of the spears start getting too spindly to be worth cutting.
When the harvest is over (early June in western Virginia), I remove the cover. The plants need full sun in summer. I apply a complete fertilizer, such as 10-10-10, immediately after the harvest and again in midsummer.