Warm winter weather and wheat

By Laura Lindsey, Ohio State University Extension

Across Ohio, the average air temperature was 8 to 10 degrees F warmer in January through Feb. 12. Due to these warmer winter temperatures, wheat may appear greener than usual and also raises the question, “Will the vernalization requirement be met?”

Winter wheat has molecular regulation preventing the transition to reproductive growth until a certain threshold of cold days has been reached. This regulation is called “vernalization.” In winter wheat, the vernalization period protects plants from breaking dormancy too early. The vernalization requirement varies among wheat cultivars and is temperature and day length dependent. In a study conducted on one winter wheat cultivar, it took 40 days for plants to achieve vernalization at 52 degrees F while it took 70 days for plants to achieve vernalization at 34 degrees F. Temperatures above 64 degrees F were ineffective for vernalization. Although winter wheat is green and the winter temperatures have been above average, the vernalization requirement will be met.

Once the vernalization requirement has been met, growth is driven by growing degree units. At this point, exposure to freezing temperatures can be a concern. However, in our research, even at Feekes 6 growth stage (first node visible and above the soil surface, usually mid- to late-April), winter wheat yield was not reduced until temperatures reached 14 degrees F for 15 minutes. As the winter continues into spring, we will be watching for this issue.