There are three basic methods to control weeds in the home garden -- cultural methods (hoeing and hand weeding), the use of mulches, and application of herbicides.
Chemical weed control is an easy and effective way to control weeds in agricultural crops. Unfortunately, there are several problems involved when using these materials in the home garden.
- There is no single herbicide that can be used to control weeds in all vegetables and flowers. Different herbicides would have to be applied to the various crop areas.
- Application methods and times may vary for the different crops.
- Herbicides often control some types of weeds, but may have little or no effect on others. For example, trifluralin (Treflan or Preen) will control most annual grasses, but is ineffective against most broadleaf weeds.
- Many herbicides are also difficult to obtain. Most are agricultural herbicides which are not available in small amounts at the local garden center.
Because of these limitations, most gardeners should rely on cultural methods and mulching for weed control. Herbicides may be used to supplement these methods in certain situations. Cultural methods include hoeing, hand weeding, and cultivating. Cultivating and hoeing should be shallow. Deep cultivation may injure plant roots and will also bring additional weed seed to the soil surface. Cultural methods should be begun early in the season before weeds become a problem. The key to effective cultural weed control is to eradicate the weeds when they are still small. Home gardeners must also be persistent.
Mulches control weeds by preventing weed seed germination. Mulches effectively control most annual weeds. Perennial weeds, however, have to be controlled by alternate methods. Mulches can be divided into two general types -- organic and synthetic mulches. Organic mulches include ground corncobs, lawn clippings, compost, straw, pine needles, wood chips, and sawdust. Synthetic or inorganic mulches include black plastic and porous landscape mats. Mulch selection is based on availability, cost, durability, appearance, and ease of application.
Lawn clippings, shredded leaves and straw are excellent organic mulches for vegetable gardens and annual flower beds. Apply these materials in early June after the soil has warmed sufficiently. Plant growth may be slowed if organic mulches are applied when soil temperatures are still cool in early spring. In the fall, these materials can be tilled into the soil.
Landscape plantings (trees, shrubs and perennials) should be mulched with organic materials, such as wood chips or shredded bark. These materials decay slowly and should last for several years.
Black plastic is most commonly used in the vegetable garden. Plants or seeds are set in holes made in the plastic. Black plastic controls weeds, but it also promotes plant growth and early yields of warm-season vegetable crops.
Black plastic is a poor mulch for landscape plantings. Plastics can trap excessive amounts of water in the soil during wet weather, damaging trees and shrubs. The porous landscape mats, however, allow water and air to pass through them. The mats are placed on the ground and then covered with wood chips or shredded bark.
This article originally appeared in the May 6, 1992 issue, p. 73.