September 19, 2013
It's that time of year again when I'm getting calls and receiving pictures of a very annoying weed in lawns. The weed is Windmill grass (Chloris verticillata), a warm-season grass that has thrived in the hot and dry period of late summer. The seedheads are just now reaching full maturity and it is readily visible in dormant Kentucky bluegrass lawns.
It produces a lot of seed on the windmill-like seed head. These seedheads will break loose when the seed is mature and it will roll across the lawn on windy days like a tumble weed and disperse the seed on surrounding areas. Next year there will be more of it.
It is relatively new in central Iowa and we are still trying to figure out how to deal with it.
Roundup will kill it non-selectively, but it is a great seed producer and it will come back. Tenacity (mesotrione) is labeled for it, but it will require persistence and you can expect new plants from seed in the spring.
Here are a few pictures that will help in identifying it.
This is a drawing of it from the Scotts Manuals on grass identification.
Seedhead found in a cemetery in Ames, Iowa.
I took the next 3 pictures this morning just outside of Nevada, Iowa, in a dormant lawn in a park area. The seedheads reach a height of 6 to 8 inches in some of the patches.