By Nathan Winter
Extension Educator, McLeod and Meeker Counties
Spring is the time that most homeowners work towards controlling lawn weeds. Pre-emergent herbicides are often used to control crabgrass and other spring germinating weeds. Typically, the best time to apply pre-emergent herbicides for lawn weeds is the middle of May. However, timing should be moved up in 2012 due to the above normal temperatures this spring. Pre-emergent herbicides can be purchased to help control those populations. Follow the label requirements for application and be sure that the product is labeled for the use you have intended it for.
Some gardeners are now using corn gluten meal because it acts similar to pre-emergent herbicides by inhibiting weed seeds from germinating. Corn gluten meal also contains a source of Nitrogen fertilizer. For best results, apply 20 pounds of corn gluten meal per 1,000 square feet and lightly water into lawn. Be sure to not apply these pre-emergent herbicides to areas where you have planted seed or plan to plant seeds. These pre-emergent herbicides are not selective for which types of seeds they stop from germinating.
According to the University of Minnesota Extension, post emergence herbicides may be applied any time the weeds are actively growing, the air temperature is 60-80 degrees F, there are no winds, and there is no rain in the forecast for 48 hours. Most effective control of perennial broadleaf weeds is obtained when applied in early fall (August 15-October 15) or in spring (May 1-June 1). For some weeds, repeated application at 20-30 day intervals may be required for control.
For dandelions, use 2, 4-D or a combination of 2, 4-D, MCPP (Mecoprop), and dicamba can also be utilized. The ideal timing for applying these products for dandelion control is September. If your weed control approach is to control dandelions in the spring, apply chemical after they have finished blooming in May. The non-chemical option is to manually dig out the plants. A weeding fork, dandelion diggers may be a couple of options for that task. Get as much of the dandelion root as you can so the dandelion does not start growing again.
For creeping charlie, use a combination of 2, 4-D and MCPP or a combination of 2, 4-D, MCPP, and dicamba. The ideal timing for applying these products to creeping Charlie is in September or autumn once temperatures have cooled to the 60's and 70's. If your weed control approach is to control creeping charlie in the spring, apply chemical while the temperature remain cool and the plant is actively growing in the beginning to middle of May. The non-chemical approaches are to pull the plant out or utilize a dethatching rake. It may be necessary to start over with the lawn if the creeping charlie gets out of control.
Most other broadleaf weeds can be controlled by herbicide applications of 2, 4-D and/or a combination of 2,4-D, MCPP, and dicamba. It is always a good idea to know what you are spraying to be sure that the herbicide will control the desired pest. The herbicide label should list the weeds it will control. Another herbicide option is to utilize a non-selective herbicide like glyphosate. Use of these types of products should only be used when spot spraying targeted weed pests. Drift on to lawns and ornamental plants will injure or kill the desired plants as well as the targeted weed pests.
A healthy lawn is very important to limit the competition of lawn weeds. Work on improving the lawn while trying to slow down and eliminate weed competition. Try to seed grass into bare areas of the lawn, fertilize, and aerate your lawn to help it compete against the weeds. When using chemicals, read and follow all of the directions for using the specific product. If you are looking for further information contact the Extension Office in McLeod County 320-484-4303 or Meeker County 320-693-5275.