Allen D. Owings, Koske, Thomas J.
Our warm-season grasses don’t like low temperatures. In fact, some may show some off color because of chilling stress that might start at 54-60 degrees F. Early chilling damage can appear as a general tan color or as a blotchy, camouflage mottling of the turf. Dead foliage is dry and not the yellow, slimy foliage that is seen with Large Patch or Brown Patch disease.
Expect warm-season grasses to discolor with the first frost. When we have a heavy frost, keep traffic or play from the turf until temperatures reach mid to upper 30s. Frosted leaf blades will break off because of fracturing ice crystals in the leaves. Melting can be hastened if temperatures are not below freezing by applying a light irrigation; then play or use may resume.
If hard frozen, turf is more prone to extensive damage from traffic. Here the leaf and shoot cells will rupture when squashed, leaving dead areas in the shape of foot prints or tire tracks. This is also true of lawns that were irrigated and frozen over or turf covered by an ice storm and then subjected to traffic or mechanically stressed.
Protecting turf from winter damage starts in September when we ensure that the sod has lower nitrogen fertility and adequate potassium. If you suspect potassium is lacking, winterize by applying some potash (1 lb./1000 sq.ft.) in early fall while the grass is still growing and can take it up. Late fall is way too late to winterize the lawn, although the extra potassium will usually do no harm.
In the late fall, you can try a light irrigation to knock off frost or apply lightweight, porous turf-enhancement covers to hold extra soil heat on the sod. Apply and remove covers as needed for frost threat and play access.
If the grass is still growing a little, raise the cutting height a notch or two to get more foliage. This added foliage cover can give extra protection from freeze damage.
In the event of a freeze or hard frost, it is important to keep all traffic off the sod until thawed. That will help keep winter kill damage to a minimum.
The LSU AgCenter and the LSU College of Agriculture