Perennial broadleaf weeds, such as dandelion, plantain, white clover, and ground ivy (alias "creeping charlie"), are common problems in lawns. Control methods include manually removing the weeds by pulling and digging or destroying them with broadleaf herbicides.
In small areas, pulling and digging are feasible means of weed control. To achieve control, gardeners must remove their entire root system as many perennial weeds grow back from underground plant parts.
Effective broadleaf herbicides include 2,4-D (2,4- dichlorophenoxyacetic acid), MCPP (2-(2-methyl-4-chlorophenoxy) propionic acid), and dicamba (3,6-dichloro-o-anisic acid). The most effective broadleaf herbicide products contain a mixture of 2 or all 3 of these compounds. Combination products control a larger number of broadleaf weed species than a single compound. For example, 2,4-D does an excellent job of controlling dandelions, but is relatively ineffective against white clover. MCPP, on the other hand, provides excellent control of white clover and only fair control of dandelions. A product containing 2,4-D and MCPP effectively controls dandelions and white clover. Broadleaf herbicide products containing dicamba are the most effective on ground ivy. The best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides is fall (mid-September through October). In the fall, perennial broadleaf weeds are actively translocating carbohydrates to their roots. Broadleaf herbicides applied to the weeds will absorbed by the foliage and translocated to the roots along with carbohydrates. This results in the complete destruction of the broadleaf weeds.
Broadleaf herbicides are applied as liquids or granules. Before applying any herbicide, carefully read and follow label directions. When applying liquid formulations, spray drift can be avoided by following simple precautions. Don't spray when wind speeds exceed 5 mph. Also, don't spray when temperatures are expected to exceed 85 degree F within 24 hours of application. Coarse droplets are less likely to drift than fine sprays. Select nozzles that produce coarse droplets and use low sprayer pressure when applying liquid broadleaf herbicides.
Granular herbicides are often combined with fertilizers. Apply fertilizer/broadleaf herbicide combinations when the foliage is wet so that the particles stick to the foliage, permitting herbicide uptake. (Broadleaf herbicides are absorbed by the foliage, not the roots.) Apply granular fertilizer/broadleaf herbicide products in the early morning when the foliage is wet with dew or sprinkle the lawn before application.
To insure adequate leaf surface and herbicide absorption, don't mow the area 2 or 3 days before treatment. After treatment, allow another 2 or 3 days to pass before mowing. This allows adequate time for the herbicide to be translocated within the weeds.
The best way to prevent future weed invasions in the lawn is to maintain a thick, healthy turf. Selection of the proper turfgrass species and good cultural practices, such as proper mowing and fertilization, should produce a dense stand of grass and provide few opportunities for unwanted weeds.
This article originally appeared in the August 25, 1995 issue, p. 128.