Landscape & Irrigation

January/February 2016

Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.

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Page 27 of 35

Deep supercooling is a way to keep a liquid in a liquid state well below its freezing point. To do this, these plants produce a special protein to prevent freezing. These are conveniently known as "antifreeze proteins" or AFPs, and they are pumped into the spaces between the cells during the fall acclimation period. AFPs work not by lowering the freezing point, but by inhibiting the re-formation of ice crystals. They also function at very low concentrations, which means they do not have the same issues related to increasing the osmotic pressure as other methods. Deep supercooling also has its range limits, but will allow trees such as oak, elm, maple, beech, ash, walnut, hickory, rose, rhododendron, apple, pear and stone fruits to survive temps down around negative 40 degrees Fahrenheit. Although that number seems ridiculously cold to our tropical-loving bodies, that is still only about half as cold as the Dahurian larch can endure. Trees such as paper birch, redtwig dogwood, willow, quaking aspen, and, of course, the Duhurian larch survive the damaging crystallization effects of freezing water by trying to rid themselves of as much water as possible. Rather than pumping more items into their cells, these plants spend the autumn pumping the water out of their cells. The water still freezes, but the crystallization occurs in the cytoplasm within the intercellular spaces, which has much less damage potential than freezing inside the cell membranes. Additionally, removing water from the cell increases the concentration gradient of solutes within the cell, which, in turn, lowers the freezing point of the cell, similar to the mechanisms mentioned earlier. The species that can best perform these tasks are those that are considered the most cold hardy and come with the reward of being able to thrive in areas unsuitable for most other living things. Even the most cold-hardy species will suffer damage from the cold if they do not acclimate to it properly. Even though water is the most damaging thing plants confront once the temps drop, it is vital to their preparation. Keeping trees well watered up until the ground freezes is one of the best ways to help them survive the coming winter. Given the proper care in autumn, and if the temps do not drop below a tree's minimum comfort range, they should be able to resume activity in the spring. If only surviving the winter was as easy for us humans. Brandon M. Gallagher Watson is creative director at Rainbow Treecare Scientific Advancements, and is an ISA Certified Arborist (#MN-4086A). Water trees even after leaf drop for better hardiness. Hardy trees withstand freezing temps for months. 28 January/February 2016 Landscape and Irrigation TREE CARE LI "Even the most cold-hardy species will suffer damage from the cold if they do not acclimate to it properly."

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