Yard and Garden: Controlling broadleaf weeds in the lawn
Fall is an ideal time for many lawn maintenance practices such as weed control. In the fall, perennial broadleaf weeds such as dandelion, creeping Charlie and thistle are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied at this time are more thoroughly absorbed and transported to the roots along with the carbohydrates, resulting in the death of the weeds. In this article, horticulturists with Iowa State University Extension and Outreach offer advice on controlling broadleaf weeds in the lawn.
How do I control dandelions and other broadleaf weeds in my lawn?
In small areas, some weeds can be controlled by pulling and digging. This method is best accomplished after a soaking rain or deep watering. It is important to remove the entire root system so weeds don’t resprout. This can be difficult for deep-rooted weeds. In many situations, herbicides are the most practical method of weed control.
Effective broadleaf herbicides include 2,4-D, MCPP, MCPA, dicamba, triclopyr and others. The most effective broadleaf herbicide products contain a mixture of two or three herbicides as no single compound will control all broadleaf weeds. Fall (mid-September to early November) is the best time to apply broadleaf herbicides in Iowa. Broadleaf herbicides can be applied as liquids or granules.
How do I control creeping Charlie in my lawn?
Ground ivy (“creeping Charlie”) in lawns can be difficult to control. This tenacious weed can be managed by pulling and digging. This method is best accomplished after a soaking rain or deep watering. Unfortunately, pulling and digging are often ineffective because rarely are all stem and root pieces removed using this method. If the ground ivy is not completely destroyed, surviving portions will continue to grow and spread.
Creeping Charlie can also be effectively controlled with broadleaf herbicides. Products that contain 2,4-D or triclopyr are most effective. Better control is achieved utilizing herbicide products that contain a mix of both active ingredients or by alternating between the two active ingredients with each application. At least two applications are necessary to effectively control ground ivy. In Iowa, the first application should be made in mid to late September, the second a month later.
How can I control violets in my lawn?
Violets (Viola species) are native to Iowa. Native habitats vary from dry, rocky prairies to moist woodlands. Violets are also found in lawns, especially in shady areas.
Violets are difficult to control in turfgrass areas. 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 herbicide products containing triclopyr usually provide good control of violets. Applications can be made in spring (during bloom) or fall. To help protect pollinators, for spring applications, mow violets just before applying herbicide to remove flowers. Two applications, two to three weeks apart, are usually necessary to achieve good control.
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, it is important to avoid spray drift problems. Don’t spray when winds exceed five miles per hour and when temperatures are forecasted 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 apply the liquid using a low sprayer pressure. 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 weed’s foliage to be absorbed. 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 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, don’t irrigate or apply these materials when rain is forecast for 24 hours.
Are there any advantages to not killing weeds in the lawn?
Some gardeners highly value the appearance of a weed-free lawn creating a beautiful, uniform, green carpet of turfgrass that highlights the home and garden beds in the landscape. This “golf course look” is not important to everyone and the presence of broadleaf weeds like dandelion, Dutch clover and violets can be acceptable for some gardeners.
One notable advantage to allowing some of these plants to grow with turfgrass is that it creates a lower-maintenance lawn that will require less irrigation and fewer chemical applications of herbicides. Many lawn weeds are not native. While it is important to not let these non-native plants grow completely out of control, letting them mingle with the turfgrass can add interest and colorful blooms throughout the year. These blooms are particularly prolific in early spring when many other plants have not yet begun to bloom, providing a food source for many insects such as bees.