Yard and Garden: Lawn Weed Control Print
News Releases - Agribusiness
Written by Joy Venhorst   
Wednesday, 31 August 2011 09:11

The overall appearance of a lawn is directly related to the maintenance provided. September is an ideal time for many lawn maintenance practices—such as weed control. To have additional questions answered, contact the horticulturists at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or call 515-294-3108.

When is the best time to apply a herbicide to the lawn to control dandelions and other broadleaf weeds?

Fall (mid-September through October) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides. In fall, perennial broadleaf weeds are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds.

Broadleaf herbicides can be applied as liquids or granules. Before applying any herbicide, carefully read and follow label directions.

What is the proper way to apply broadleaf herbicides to the lawn?

Broadleaf herbicides can be applied as liquids or granules. Before applying any herbicide, carefully read and follow label directions. When applying liquid formulations, potential spray drift problems can be avoided by following simple precautions. Don’t spray when winds exceed five miles per hour. Also, don’t spray when temperatures are forecast to exceed 85 degrees Fahrenheit within 24 hours of the application. Since 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. When spraying, keep the nozzle close to the ground. If only a few areas in the lawn have broadleaf weed problems, spot treat these areas rather than spraying the entire lawn. Apply just enough material to wet the leaf surfaces.

Granular broadleaf herbicides are often combined with fertilizers. Apply granular broadleaf herbicides and fertilizer/broadleaf herbicide combinations when the weed foliage is wet. Broadleaf herbicides are absorbed by the weed’s foliage, not its roots. To be effective, the granules must stick to the weeds and the herbicide must be absorbed by the weed’s foliage. Apply granular products in the early morning when the foliage is wet with dew or irrigate the lawn prior to the application.

To ensure adequate leaf surface and herbicide absorption, don’t mow the lawn two to three days before treatment. After treatment, allow three or four days to pass before mowing. This allows sufficient time for the broadleaf weeds to absorb the herbicide and translocate it to their roots. To prevent the broadleaf herbicide from being washed off the plant’s foliage, apply these materials when no rain is forecast for 24 hours. Also, don’t irrigate treated lawns within 24 hours of the application.

How do I control creeping Charlie in my lawn?

Ground ivy (“creeping Charlie”) in lawns can be controlled with broadleaf herbicides. Products that contain 2,4-D or triclopyr are most effective. 2,4-D is an active ingredient in many broadleaf herbicide products. Triclopyr can be found in Ortho Weed-B-Gon Chickweed, Clover, and Oxalis Killer for Lawns and a few other products. In Iowa, herbicide applications should be made between mid-September and Nov. 1. Two applications are necessary to effectively control ground ivy. The first application should be made in mid to late September, the second a month later.

How do I control violets in my lawn?

Violets are very difficult to control. Digging up the plants is an option for home gardeners with a small infestation of violets. Broadleaf herbicides are the most practical solution when dealing with large numbers of violets. Broadleaf herbicides containing triclopyr usually provide good control of violets. Applications can be made in spring (during bloom) or fall. Two applications, two to three weeks apart, are usually necessary to achieve good control.

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