University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Warm Season Grasses Turn Lawns Brown

October 12, 2000

Have you noticed patches of brown or straw-colored grasses in your lawn this fall? Is the entire lawn now a straw color? Most likely the cause is warm-season grasses growing in the lawn. Annual species are dying, perennial species are just going dormant.

Most grasses in northern Illinois lawns are cool-season species, which stay green for weeks after warm season species have turned brown. Warm-season grasses turn brown with cooler weather in fall, and perennial species do not return to green until very late next spring or early summer. Warm-season annuals die and must regrow from seed to appear next season.

Zoysiagrass is the most common perennial warm-season grass in our area. During a hot summer zoysiagrass lawns are most likely the greenest on the block. Then with the return of cool weather in September, zoysiagrass starts turning yellow, then a straw color. Zoysiagrass is not dead, but it will not green up until significant warmth returns sometime next year.

Often the patches get larger over time, or never seemed so noticeable. Zoysiagrass does well in hot weather and invades the rest of the stressed lawn, so the patches get larger.

One control option for zoysiagrass is to dig it out, making sure to get all the stolons and rhizomes (creeping stems). Another option is to apply the herbicide glyphosate (Roundup, Kleeraway), but the grass needs to be green and growing to be killed. Probably the best time to do this would be next August, so the area can be reseeded afterwards.

An additional warm season grass that appears as straw-like patches in fall is nimblewill. Nimblewill will appear as patches of fine grass, usually in shade locations. These patches become very conspicuous in fall and next spring. Control options are the same as for zoysiagrass.

Finally, warm-season annual grasses will also brown out as they die off in fall. Crabgrass leads the list. Usually the area will be out in full-sun in a lawn area that was thinning for some reason. The main difference is crabgrass is dead, and the same plant will not return next season. Seeds on the soil surface must germinate next year for the problem to occur again. Preemergence herbicides (crabgrass preventers) can be used next season to help prevent the return of crabgrass in the lawn.


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