Get Ahead of the Weeds

Complete control of weeds in the home lawn or garden is not a practical goal for many homeowners. A more realistic approach is to minimize weed populations through various control measures. Iowa State University horticulturists provide guidance on weed control methods. To have additional questions answered, contact Hortline, the ISU Extension and Outreach horticulture hotline, at 515-294-3108 orhortline@iastate.edu.

How do I control weeds in my garden?
Cultivation, hand pulling and mulches are the primary means to control weeds in the home garden.

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 on a regular basis through the growing season. Small weeds are much easier to control than large weeds. It’s also important to destroy weeds before they have a chance to produce seeds.

Mulches control weeds by preventing the germination of 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.

What materials would be a good mulch for a vegetable garden?
Grass clippings, straw and leaves are excellent mulches for the vegetable garden. Allow lawn clippings to dry before applying them to gardens. A thick layer of fresh grass clippings may get hot and produce an unpleasant odor. If the lawn has been treated with a broadleaf herbicide, don’t use the clippings until the lawn has been mowed two or three times after the application. Straw should be free of crop and weed seeds. Suitable materials include wheat, oat and soybean straw.

Leaves should be shredded or composted before applied as a mulch. Shredded or composted leaves are less likely to blow away in the wind. Apply mulching materials to the vegetable garden in late May or early June after the soil has warmed up. Applying a mulch to cool soils in early spring will slow plant growth and delay fruiting of warm season crops, such as tomatoes and muskmelons. A mulch depth of 2 to 4 inches is appropriate for vegetable gardens.

Can herbicides be used to control weeds in the garden?
Herbicides can be used to supplement cultivation, hand pulling and mulches. However, several limitations prevent the extensive use of herbicides in the garden. Only a small number of herbicides are available to home gardeners. Additionally, most home gardens contain a wide variety of fruits, vegetables and flowers. No one herbicide can be safely used around all garden and landscape plants. If not applied properly, herbicides may cause unintended damage to fruits, vegetables and ornamentals. If you decide to use an herbicide, carefully read and follow label directions.

Source: Richard Jauron and Willy Klein, Iowa State University