October 2, 2014
On April 2, 2014, I posted some information on the very cold winter that we had just emerged from and its affect on warm- and cool-season grasses. It was the 9th coldest winter in 141 years. This summer was surprisingly wet and mild and the cool-season grasses recovered fine. The big question this season was how would the warm-season grasses like bermudagrass (Cynodon spp) and windmill grass (Chloris verticullata) that have moved into our region in recent years. These species are very susceptible to cold and I had speculated that their populations would be greatly diminished by the cold winter.
I was wrong. Both bermudagrass and windmill grass survived just fine. This is a bit confusing. We have assumed that it was our cold winters that kept these species from being a problem in the past and that the recent warm winters were the cause of their increase in the region. If that were the case, a very cold winter should have killed them.
In the case of windmill grass, it could be the fact that seed had built up in the soil and that germination during the summer was the cause of its return. That is not what I have observed, the stolons from last year recovered. Likewise, bermudagrass came back form plant parts.
I can only speculate that it would take a series of cold winters to eliminate these grasses from the region. It is something that I will keep track of the next few years. They are likely here to stay.
Windmill grass seedhead.
Windmillgrass in central Iowa lawn.
Bermudagrass incentral Iowa lawns (nest two pictures.