Asparagus Is a Giving Plant
It is surprising how many gardeners have approached me with questions regarding controlling weeds in their asparagus beds. I am glad to see a growing number of gardeners growing asparagus because it is a crop that you have to plant only once for many years’ harvest. It is a delicious vegetable that can be grilled, steamed, marinated or smothered with Hollandaise sauce or cheese. This year I planted a new bed of an only-male purple variety. Male plants are preferred because they do not develop seeds but produce more spears.
It is difficult to control weeds with a hoe during the cutting season, as it often results in cutting or damaging the spear tops or scarring the stems of spears that have emerged.
When the soil is dry, I use an onion hoe. Pushing the blade forward and pulling backwards on the surface of the dry soil is generally sufficient to sever the top of the young weeds from their roots while hardly disturbing the soil or damaging the spears. However, this year we have not had the opportunity to see dry soils, and the scraping technique does not work well on wet soils.
This year, I have been spraying young weeds with horticultural vinegar immediately after cutting asparagus. (Horticultural vinegar is available from www.amleo.com.) I use very low pressure and direct a coarse spray on the weeds. If you accidentally spray a young emerging spear, it will only scorch the surface lightly, which may detract from the appearance but will not harm the flavor when cut and cooked. Horticultural vinegar is strictly a contact weed killer, but it is deadly on young tender weeds.
To succeed in growing asparagus, you need to keep the bed weed-free through the year. I can remember when home gardeners sprinkled rock salt over the asparagus beds to control weeds. However, following repeated applications over several years, they would see their yields decline due to salt accumulation in the soil.
My method of keeping the asparagus weed-free through the year is to hand-weed the bed soon after the last cutting of asparagus and apply Preen, a pre-emergent herbicide, as recommended. Preen is a very mild weed killer containing fluoride. Two applications approximately six weeks apart are generally adequate for controlling weeds during the growing season.
In late September, I sow winter rye grass over my asparagus bed as well as in my garden. The rye grass suffocates winter weeds over late fall and winter months. In the spring, I mow down the rye grass and rototill the beds shallow so as not to damage the roots of the asparagus plants. I do not mulch my asparagus beds. Mulching asparagus beds delays early spring growth.