Weeds are those annoying plants that gardeners love to hate. In the garden, weeds compete with desirable plants for water, nutrients, sunlight, and growing space. They may also harbor insects and diseases. Allowed to run rampant in the garden, weeds can drastically reduce yields of fruits and vegetables. They also hinder the performance of annual and perennial flowers.
The first step in weed control is identification of the weed or weeds. The type of weed helps determine the best method of control. The two main types of weeds are annuals and perennials. Annual weeds germinate from seeds, grow, flower, set seed, and die within one year. Perennial weeds live for three or more years. Perennial weeds may die back to the ground in the fall, but sprout from their crowns or roots in the spring. Weeds can also be classified as broadleaf weeds or grasses.
There are three general methods of weed control in the home garden: cultivation (hoeing and tilling) and hand pulling, mulches, and herbicides.
Cultivation and hand pulling effectively control most annual weeds. Perennial weeds are often more difficult to control. Repeated cultivation or the use of herbicides are often necessary to destroy some perennial weeds. When cultivating the garden, avoid deep tillage. The roots of many vegetables, fruits, and flowers grow near the soil surface. Deep cultivation will cut off some of these roots. Also, deep cultivation will bring deeply buried weed seeds to the soil surface where they can germinate. Hoe or till around plants or between rows and pull weeds close to plants. To effectively control weeds, cultivation and hand pulling must be done periodically through the growing season. Small weeds are much easier to control than large weeds. It s also important to destroy the weeds before they have a chance to go to seed.
Mulches control weeds by preventing the germination of annual and perennial weed seeds. Established weeds should be destroyed prior to the application of the mulch. In addition to weed control, mulches help conserve soil moisture, reduce soil erosion, prevent crusting of the soil surface, keep fruits and vegetables clean, and may reduce disease problems.
Grass clippings, shredded leaves, and weed-free straw are excellent mulches for vegetable gardens and annual flower beds. Apply several inches of these materials in early June after the soil has warmed sufficiently. Plant growth may be slowed if these materials are applied when soil temperatures are still cool in early spring. Grass clippings, shredded leaves, and similar materials break down relatively quickly and can be tilled into the soil in the fall.
Wood chips and shredded bark are excellent mulches for perennial beds and areas around trees and shrubs. Apply two to four inches of material around landscape plantings. These materials decay slowly and should last several years. However, it will be necessary to apply additional material annually to retain the desired depth.
Herbicides can be used to help control weeds in the home garden. Cultivation, hand pulling, and mulches should be considered the primary means of weed control. Herbicides can be used to supplement these methods. Several limitations prevent their extensive use in the garden. (1) There is no single herbicide that can be used to control weeds in all vegetables and flowers. Different herbicides often have to be applied to the various crop areas. (2) Application methods and times may vary for different crops. (3) Herbicides may control some types of weeds, but may have little or no effect on others.
Two herbicides that may be helpful in the home garden are trifluralin (Preen, Miracle-Gro Garden Weed Preventer, etc.) and DCPA (Dacthal or Acme Garden Weed Preventer). Both products are preemergence herbicides. They must be applied before the weed seeds germinate. Established weeds should be eradicated prior to application. Before puchasing a preemergence herbicide, check the label for the list of vegetables and ornamentals for which the herbicide has been approved.
A postemergence herbicide that can be used in the home landscape is glyphosate (Roundup) Glyphosate is a non-selective, systemic herbicide. It is absorbed by green, actively growing plants and translocated throughout the entire plant. Glyphosate kills virtually all plants that are directly sprayed. Roundup can be used to control difficult-to-control perennial weeds around trees, shrubs, and in perennial beds. Do not spray or allow glyphosate to drift onto nearby desirable plants.
This article originally appeared in the 6/20/2003 issue.