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Rhonda Ferree's ILRiverHort

Rhonda Ferree's Horticulture Blog
crabgrass

Control Crabgrass in the Lawn NOW


The odd weather patterns over the past few years have played havoc on my lawn. As a result, I now have out-of-control crabgrass in areas of my front yard.

Crabgrass is an annual weedy grass that, from a distance, blends into your lawn during the summer. Upon close inspection, it can be identified by its wide leaf blade and light green color. During the summer, this low growing weed can also be identified by its seed spike that looks like a turkey foot. The seeds turn a lovely maroon color with cool fall temperatures. Crabgrass plants die with the first frost and do not overwinter. Throughout the winter they appear as splotches of brown soil throughout your green lawn.

Understanding how this plant grows will help you manage it better. Crabgrass only lives one summer and has to restart from seed each spring. Crabgrass seeds germinate when spring soil temperatures are about 55 degrees for 7 to 10 consecutive days. New plants will continue to pop up until soil temperatures are 90 degrees. Soil temperatures at the Illinois State Water Survey's Peoria weather station show that bare soils warmed to 55 degrees on February 22, but since then have hovered in the mid 40-degree range.

The primary means of controlling crabgrass is by providing a vigorous, dense, competitive turf. Thin, weak lawns that show a bare soil between grass plants allow the weed to grow. One way to decrease these bare soil areas is to mow your grass higher. Most of the grasses we grow in central Illinois should be mowed between 2 and 3 inches tall. Shorter mowing stresses the plant, making it weak and susceptible to weed and other pest infestations.

If crabgrass is out of control in your yard, you can use a preemergence weed killer to control it before it germinates. The "crabicide" forms a chemical barrier or blanket at the soil surface that prevents crabgrass development from germinating seeds that have absorbed the weed killer.

Since our soils will soon warm to crabgrass germination temperatures, now is the time to apply crabgrass control products. Since most of us do not have soil thermometers, another good gauge is to apply these products about the time forsythia bloom, and they are in full bloom throughout central Illinois now.

Both synthetic and organic herbicides are available. Check the ingredient statement on the product's label. Corn gluten is an example of an organic pre-emergence herbicide. Organic products require a little more time to break down and need watered in lightly in order for particles to come in contact with soil microbes and begin activation. As the plant proteins of the organic fertilizer (corn gluten) breakdown, a natural plant toxin is released which serves as a partial pre-emergent. This product does not give 100 percent control but is an option for those that prefer organic products.

You can find more information on lawn care at our University of Illinois Extension LawnTalk website at http://urbanext.illinois.edu/lawntalk/.



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