The Lawn May Still Need Work Says ISU Extension Office

Despite the snow on the ground and even though it may be a bit colder than most people expected at this point in October, fall is a great time to fertilize, control weeds and prepare your lawn for next year according to the ISU Extension Office. This week’s Yard and Garden entry answers some common questions about fall lawn care, and comes from comes from Adam Thoms, assistant professor and extension turfgrass specialist with Iowa State University Extension and Outreach.

When can I stop mowing the lawn in the fall?

Continue to mow the lawn until the grass stops growing in the fall. The foliage of cool-season grasses, such as Kentucky bluegrass, stops growing when daytime high temperatures are consistently below 50 degrees Fahrenheit. In central Iowa, bluegrass usually stops growing in early to mid-November. Once the foliage stops growing, the lawn mower can be put away for the winter.

When should I fertilize the lawn in the fall?

Fertilizer applications can be made in mid-September and late October/early November. Mid-September fertilization promotes a moderate rate of shoot growth and helps to thicken the turf. An application of fertilizer in late October/early November (at the time of the last mowing) promotes root growth and early green-up next spring. Apply 1 pound of actual nitrogen per 1,000 square feet in mid-September and late October/early November.

When is the best time to apply a broadleaf herbicide to the lawn?

Fall (mid-September to early November) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides, even after the first frost. 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. Spring applications are generally less effective than fall applications.

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

I just seeded my yard, can I spray for broadleaf weeds?

Most broadleaf herbicides should not be sprayed on newly seeded turfgrass until after the area has been mowed twice. You can start mowing a newly seeded area once the yard has grown to 3 inches tall, and you can mow it at 2 to 2.5 inches height of cut. After you have mowed twice, you can spray most broadleaf herbicides.

Do I need to remove the leaves on my lawn?

Turfgrass plants utilize light, water and nutrients to manufacture food. In fall, lawn areas beneath large trees are often completely covered with leaves. The leaf debris prevents the turfgrass plants from manufacturing and storing food prior to winter. A thick layer of leaves (little or no grass is visible) will need to be raked up and removed, or the mower will need to cover the area in multiple directions to chop up all of the leaves. It’s possible to deal with a thin layer of leaves (areas of grass are clearly visible) by chopping them up with a mulching mower. After mowing, the turfgrass should be fully visible.