Judging from the number of Hortline calls concerning weed control, 1993 must have been the year of the weed. Gardeners have several options when it comes to controlling weeds in the vegetable garden. The oldest method of weed control comes with cultivation, either hand hoeing or through the use of a rototiller. Cultivation works well for annual weeds such as crabgrass or purslane. However, with perennial weeds, cultivation may initially create a larger problem. Cultivation breaks perennial weeds and their root systems into smaller pieces which grow into entire plants. Frequent cultivation is often needed to control perennial weeds. Be sure to remove as many weed parts as you can so the weeds are not allowed to reroot and grow. A second disadvantage of cultivation is that many vegetables have shallow root systems. Frequent cultivation can damage their roots and reduce potential yields. Use care when cultivating around such plants as squash, cucumbers, melons and tomatoes.
Mulches, both organic and synthetic, can be quite effective in reducing or eliminating annual weeds. Synthetic mulches, such as black plastic, are also effective for controlling perennial weeds. Unfortunately, most perennial weeds have enough food reserves to push through a layer of organic mulch. Mulches prevent light from reaching the soil surface and inhibit weed seed germination and growth. Mulches also conserve moisture, prevent erosion, and reduce soil compaction. Organic mulches also keep soil temperatures from rising to high levels. Apply organic mulches, such as grass clipping, straw, or shredded leaves, after the soil has had a chance to warm in the spring. Warm season crops require warm soils for good growth. Another advantage of organic mulches is they return valuable organic matter to the soil as well as small amounts of nutrients.
A final method of weed control involves the use of herbicides. Both pre-emergence and post-emergence herbicides are available for use in the garden. Pre-emergence herbicides are an effective way to control annual grasses and some annual broadleaf weeds. Pre- emergence herbicides work in different ways to prevent the seedling from emerging through the soil surface. Two pre-emergence herbicides are commonly used in the home garden, Dacthal (DCPA) and Treflan or Preen (trifluralin). Both control a number of weeds and can be used with many garden vegetables and flowers. It is important to remember that neither one can be used with every garden plant. Be sure to read the label for a list of vegetables and the proper vegetable plant stage for herbicide application. If your particular vegetable is not on the label, the product can not be used. Another type of herbicide commonly used in the vegetable garden is the non-selective herbicide, glyphosate (Roundup or Kleenup). Glyphosate can be used in the garden prior to planting several garden vegetables. After 7 days, the seeds, rooted cuttings, or transplants of many garden vegetables can be planted. The biggest exception is tomatoes. Tomato transplants cannot be planted for 30 days; however, seeds may be planted 7 days after the use of glyphosate. Again, the label lists the plants and proper waiting intervals for planting.
The 1994 gardening season looks like a year for retaliation after a gardening season lost in 1993. Through the combined use of the weed control methods listed above, I hope this summer will be enjoyable instead of back breaking.
This article originally appeared in the April 27, 1994 issue, p. 53.