Winter canola and recent freezes

With recent freezes across the region, there will probably be several questions over the next couple of days and weeks regarding the status of the canola crop.  It has been said and it could not be any truer, no two freeze events are the same.  This is definitely true for the freeze event that was experienced nearly statewide over the weekend.  Many factors play into the severity of a freeze event, these will include: how cold were the temperatures, length of the freeze event, and stage of the crop.  For the most part, this last freeze did not play nicely with any of these factors.  Quite a bit of the crop was nearly flowering or at beginning flower.  Most folks experienced with canola will tell you that the bottom third of the canola raceme hold a fair amount of total yield (in a typical season).  For those with fields flowering, the temperatures were cold enough for a prolonged period of time that we could see some decent loss of flowers on these primary stems.  This is because all the flower exposed to this freeze event will typically go sterile and not produce a viable pod.  Those producers that were at bolting or at late rosette, the canola should be in a much better place.  Most of the canola that I found today presented with crooked stems that did not bend beyond half-way down the plant.  Plants should have adequate time to correct this and produce and adequate main stem.  Furthermore, most buds that were not quite at the flowering stage looked good and should have been protected against the cold weather and still should produce flowers.

Canola plant with stem bending typically associated with freeze damage, 2014 freeze (Josh Bushong, Oklahoma State University).

As with most crops following a freeze event, the conditions over the next several days and weeks will determine how much yield was lost.  If the weather cooperates over this period, even the most severely damaged canola should put on further axillary buds and be able to put on additional flowers.  This indeterminate nature is a value of canola during these later freeze events.  As opposed to wheat, where if the head of a tiller is killed that tiller is no longer productive, canola can still produce yields from that primary stem.  If good growing conditions present, the canola plant may still produce but will likely be delayed.  The fear from the delayed maturity of the plant will be the plant maturing into less favorable conditions.  This is especially true regarding flowering during months that typically have much higher average temperatures.  This could result in poor pollination which in turn will result in poor pod set. 

Several other questions have arisen, particularly regarding the impact the drought conditions will have on the canola plant heading into a major freeze.  This should have little to maybe a slightly positive effect.  A more stressed plant will produce physiological features to handle this stress, this could result in less impact on the plant due to the freeze.  The primary concern regarding the dry conditions prior to this freeze will be on the limited vegetative growth following green-up that much of the state has experienced.  This lack of vegetation could leave more limited reserves for the plant to catch up and the plant will be more reliant on cool, moisture conditions over the next several days to weeks. 

To evaluate the damage of the canola, most will have to wait for adequate growing conditions to return.  Based on the 10-day forecast, this could be the end of next week or the week following.  If the reproductive structures continue to progress, whether that be continue to grow or to produce flowers, the plant should be able to adequately yield.  If sub-optimal conditions come over the next several days, the yield potential could be damaged.  With a freeze of this magnitude, growers should expect to see some gaps in the flowering structure and potential stem splitting when they return to the fields next week.  This stem splits have less an impact on yield but a higher potential impact on stalk strength and standability later in the season.  Higher amounts of split stems will result in higher amount of lodging and potential decreased harvest efficiency. 

Split stem following a major freeze event.  This may cause issues with stem strength and potentially increased lodging (Photo used with permission from Dr. Mike Stamm, Kansas State University).

With growers assessing the damage over the next several days for both wheat and canola, growers can take solace in that canola has very good resilience and can rebound from these events.  As of now, we must take time to let both plants try to rebound and produce adequate yields for these two critical winter crops.   


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