Snow, freezing temperatures on four to five nights and in some areas, heavy frosts (as low as minus 7°C), occurred across the Prairies last week. This may prompt canola growers to consider reseeding. However, resist the urge to reseed immediately, as recovery may turn out to be better than expected, especially if seed has not yet germinated or the young seedlings have become acclimated to the cold. Snow may actually be beneficial as it can act like a blanket and insulate the crop, especially if the snow cover came prior to the most severe freezing temperatures. If the seed has not germinated and is still hard/firm, not soft/mushy, it will likely survive and just needs warmer conditions. After several days of near freezing temperatures, emerging canola that is near the surface or that emerged under cool conditions will undergo a gradual hardening process, allowing the plants to withstand freezing temperatures without serious damage. Studies have shown that early-seeded canola seedlings that had undergone hardening could withstand minus 8 to minus 12°C temperatures. Cooler conditions result in plants that are slower growing, producing smaller cells that have a higher concentration of soluble substances that make them more resistant to frost damage. This hardening off process helps defend plants against the chain of plant gene activities set off by cold weather that produce or degrade the proteins that protect plant cells. Wait at least three to five days or longer depending on growing conditions before making any decisions on canola crops. The desired plant population is approximately 10 plants/ft2 but lower plant populations (as 3 to 4 plants/ft2 in some circumstances) can be adequate, especially in late-emerging stands. It will likely be better to leave a thinner stand (provided it is unitform) than take the risk of late reseeding because maturity/early fall frost becomes a concern.
For more information on assessing frost damage in canola see the following link: https://canola-council.merchantsecure.com/canola_resources/product37.aspx