Cool weekend temperatures have prompted some concern about possible injury to the wheat crop.
The effect of cold weather depends on the wheat growth stage. Maximum resistance to cold weather occurs in December-February. As wheat greens-up, the plant becomes less tolerant of freezing temperatures. At Feekes 6 growth stage aka “jointing” temperatures of ≤24°F for at least two hours may be injurious. Currently, in Ohio, most wheat is at Feekes 5 (green-up), so injury should be minimal.
Currently, we are in the process of evaluating freeze tolerance of winter wheat grown in Ohio. We collected wheat samples from Pickaway County on March 30 when plants were at Feekes 5 growth stage. Plants were put into a freeze chamber and temperature lowered to 27°, 21°, 14°, and 5°F. Very little injury has been observed between 14-27°F. At 5°F, wheat leaves wilted and had a dark purple-green water-soaked look 24 hours later (see picture). We plan on re-running this study at Feekes 6 growth stage.
Reference. Shroyer, J.P., M.E. Mikesell, and G.M. Paulsen. 1995. Spring Freeze Injury to Kansas Wheat. Agricultural Experiment Station and Cooperative Extension Service. Available at: http://www.ksre.k-state.edu/bookstore/pubs/C646.PDF