CO-Horts Blog

Sunday, November 23, 2014


Tony Koski
Extension Turf Specialist

No, Elsa, this isn’t about you..

A very frozen dandelion...still alive
Some have asked, on the heels of the recent “polar vortex” (not really…it was just a sign that winter is about that here) and temperatures hovering near zero, about how the early and abrupt cold snap might affect turf pests – weeds, fungi, and insects? The short answer (in case you want to leave now and hear Elsa sing…again) is that it likely had little effect on any turf pests – and is unlikely to affect turf pests in 2015.

There were plenty of signals (fewer hours of daylight, cooler temperatures, frost) this fall to
encourage our lawn grasses (the good ones…and the perennial weedy ones as well) to ready themselves for winter. Insects that overwinter as adults, larvae, or pupae likewise were readying themselves for diapause (insect “hibernation”). Perennial weeds like dandelion, thistle and beloved bindweed were preparing themselves for winter dormancy well before last week’s chill arrived. The spores and mycelium of fungi (it was a good fall for powdery
Knotweed (Polygonum aviculare), a summer annual,
still alive after subzero temperatures!
mildew and rust on turf) are so resistant to temperature extremes that the arrival of 0 F went unnoticed by them – so they will be back next year, without question.

Seedling downy bromegrass (aka cheatgrass) thriving in
our chilly pre-winter cold snap
Even the seedlings of our winter annual weeds - species that germinated this past late summer/fall and will complete their life cycle in the spring – appear to have been completely unaffected by the week of extreme cold. The henbit, annual bluegrass, chickweed and cheatgrass I’ve looked at in the past few days appear perfectly healthy. So, I'm sorry to dash any hopes you had about any potential benefits that the recently departed cold front might have had on the pests in your lawn. They really didn’t notice. If you had any hopes of the misnamed polar vortex eliminating some of next year's turf pests, all I can say is … let it go…let it go……..


  1. (Chuckle) Informative and useful - as always. Thanks for the post!

  2. Got a good laugh, even though you dashed my hopes of not having to battle henbit in the spring.

  3. I will try to let it go, but that song won't leave my head. But I do have a question. I seeded some spots in my lawn fairly late in the fall with bluegrass and ryegrass. The seed grew and the plants are up, but quite young. Do you think that they survived the zero temperatures? They look alive to me, but I'm betting that there is more to it than just looking at them? If you think they are still ok, is there anything that I can do to help them make it through the winter? I live in Denver. Thanks. All of you bloggers are great writers and funny too. I always learn something from reading your blog. Thanks again.

  4. Hi Todd,
    Since both bluegrass and ryegrass are cool season turf species, there's a good chance they have survived. The best thing you can do to keep them alive until spring is to use every opportunity during winter to give them water (on days above 40 degrees). The next few days would be ideal. Try to water your new grass seedlings at least once a month, but more if the weather allows. Good luck! And thanks for reading and the nice comments.

  5. We were on a golf course just north of the Arctic Circle on Grimsey Island, Iceland in late October. We even saw dandelions there!