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Plants And Cold Weather
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The area has finally experienced a blast of winter. Lows well-below freezing and a day where temperatures never rose above freezing. Livestock and other mammals can cope pretty well with adequate food and water. Reptiles and certain mammals hibernate. Birds migrate. But how do plants such as our 2017 wheat and canola crop cope? What about perennial plants like prairie grasses and alfalfa? They usually cope better than we expect.
• First, all plants having to survive winter survive better with good but not excessive soil moisture. This helps in two ways. First, well hydrated roots are better able to withstand cold than under drier conditions. Second, moist soils maintain heat better than dry soils and the soil temperature fluctuates less with moisture. Typically, most plant species can survive pretty extreme cold if the soil isn’t dry. Also plants benefit from an insulating layer of snow and/or ice to protect the root system.
• Biennials, plants growing vegetatively the first year and flower the second year, accumulate large reserves of carbohydrates during the summer in their taproot. All the aboveground vegetative growth dies back over the winter and when conditions improve in the late winter/spring, biennials use these reserve to reestablish above ground vegetation and flower. These are many of our root crops such as sugar beet, turnip, radish and carrot. Flowers such as hollyhock and sweet William are biennial. Parsley and members of the onion family fit here. The need to store carbohydrates in roots also fits our next group perennials.
• Perennials such as alfalfa, prairie grasses, and problem weeds such as yellow nutsedge and bindweed. These plants survive winter, as in biennials, by accumulating carbohydrates in their root system. The difference here is that for forage crops producers must time the last cutting or remove grazing livestock with adequate time left for adequate leaf growth to replenish the roots and get ready for winter. While both grass and broadleaf perennial crop prefer moist soils, grasses with a shallower, fibrous root system tend to be more easily damaged by cold in dry soils. Some of these plants, such as yellow nutsedge also have underground horizontal stems termed rhizomes from which to produce new plants in the spring. These plants also experience complete aboveground dieback of above ground vegetation. Perennial pastures also benefits from residue on the soil surface to help insulate the soil.
• Annual crop plants such as winter canola and wheat have several coping mechanisms. What is important in helping these plants transition to surviving winter is a gradual cool down to go along with decreasing day length to “harden off.” Both canola and wheat exhibit prostrate, not vertical fall growth so they are closer to the soil surface. Their cell chemistry changes and they accumulate various compounds which act like antifreeze and lower the freezing point of cell contents. Both can lose their aboveground vegetation and still be fine with adequate moisture and nutrition after dormancy. Wheat has the advantage of having the growing point located at planting depth which provides protection. Canola’s is at the soil surface so it’s more vulnerable but as long it doesn’t start to elevate and there is good soil moisture, it can withstand fairly severe cold. Again a blanket of snow also helps.
Space doesn’t allow but there is more that plants do to overwinter and the interaction of the weather with plants.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207