Updated December 20, 2024. Wheat requires a vernalization period of 6 to 8 weeks at temperatures below 8 degrees C, this will trigger flowering of the wheat next spring. Cold tolerance or Hardening off, develops slowly over time as temperature at the crown, 1 to 2 inches below ground drops below 8 C and continues to decrease. Often in SW Ontario complete hardening or maximum cold tolerance is not fully complete until mid to end of January. The hardening process reduces moisture content of crown cells and increases soluble sugar content which acts like antifreeze to reduces cold damage to the crown cells.
We are starting the Fall planting season for winter wheat, GDD accumulations as of Sept 1st 2024. It takes 80 GDD for germination and an additional 50 GDD for each inch of planting depth for emergence to occur. It takes roughly 80 to 90 GDD for each subsequent new leaf to appear.