Assoc. Professor & Extension Turf Specialist
Across many areas of Michigan night time low temperatures dipped into the mid to high 20’s on Monday morning, May 13. While this event didn’t appear to be a serious killing event for many ornamentals I have observed some interesting freeze injury on turfgrasses. My experience with this type of freezing event is that the symptoms mimic foliar burn from a fertilizer or pesticide application. The visual symptoms to look for are on the leaf blade. If you look closely you’ll notice the old leaf blades were burned/discolored from the leaf tip down about an inch. Typically this damage is observed on higher cut turf, i.e. lawn height, and will disappear with new emerging growth and the next mowing.
|Freeze injury mimics fertilizer burn or dull mower blade.|
|Freeze injury results in leaf tips 'burning back' a couple inches.|
In addition to the typical burning look on the leaf tips I’ve also observed some very interesting freeze injury symptoms on different species. Tall fescue clumps, contaminating a Kentucky bluegrass turf displayed freeze damage much greater than the bluegrass to the point it looks like someone sprayed them with RoundUp.
|Tall fescue clumps suffered freeze injury.|
The lush, rapidly growing turf from a type II fairy ring suffered freeze injury that mimics what usually happens later in the summer from drought stress.
|Rapidly growing turf in fairy ring was damaged.|
One type of freeze injury that brought a smile to my face was viewing the tip of quackgrass leaf blades burned down at least a couple inches from the freezing temperatures. Unfortunately I doubt this will slow down the quackgrass for very long.
|Quackgrass leaf blades suffered only minor injury.|
My theory for the damage to the fescue clumps, fairy ring, and quackgrass are that any rapidly growing, young leaves, were more susceptible to freeze injury than the slower growing or mature leaves. Observing these symptoms also made me think about winterkill and the importance of turf not going into winter in an actively growing state where a rapid temperature drop would not just burn back some leaf blades but potentially kill the plant.