First, there is nothing to report on the drought front. The area growing from abnormally dry to moderate drought, as is the severe condition, is expanding north and eastward but overall little has changed. With all the concern over possible wheat lost from cold temperatures combined with the drought, it might be helpful to understand how cool season plants such as winter wheat and canola adapt to survive winter. First let’s tackle monocots, grasses, like winter wheat and then dicots, broadleaves like winter canola.
The goal of a winter annual like winter wheat is to establish itself before winter, protect itself during winter, and then resume vegetative and reproductive growth after the danger of winter is past. And to produce physiologically mature seed before the heat of summer. So how does it do this and how does it know winter is coming?
• As a monocot, the growing point where new growth originates stays below the surface until mid to late March around here. It is at the planting depth which is why a depth of one inch is recommended as a minimum depth. This provides a less variable, warmer environment that the atmosphere. Dry, bare soil with poor vegetative growth and persistent cold air temperatures can lower soil temperature at the growing point below freezing and potentially damage or kill the growing point but the plant has other adaptations.
• As the cues for winter are noted by the plant, several physiological changes occur. Plant growth is prostrate, not upright. The chemistry of the plant cells changes and essentially produces antifreeze to lower the freezing point of the cell to prevent the formation of ice crystal and rupturing of cell membranes. The plant is most winter hardy at the start of winter and the level of protection decreases as winter proceeds and spring approaches. The plant can regain a level of winterhardiness if temperature decreases aren’t too rapid. And once the plant has jointed and the growing point is above the soil surface there is essentially little protection except for a lush stand. So what keys these changes?
• Two things cause the changes: daylength and temperature with daylength being more important. The plant has to prepare for winter before winter arrives so temperature isn’t as useful to the plant as decreasing daylength. The decrease in sunlight keys the changes listed previously and this is reinforced by decreasing temperatures. If the change in temperatures is too early or abrupt the plant is in trouble. So how does the plant leave dormancy?
• As daylength increases after late December as we are seeing now, that keys the plant to resume growth and it is upright not prostrate. Combined with warmer air temperatures and hopefully moisture, the plant breaks dormancy and heads towards flowering. So how does it know it is okay to flower? Winter wheat has to accumulate so much cold before it will flower. The amount varies by variety but without the requisite cold accumulation it won’t flower. All of this combines to allow the plant the best chance of being able to escape winter and not reproduce until it is safe to do so.
Next week: winter canola.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.