People always think of harsh winters causing damage to woody plants but could anything problematic come from a mild winter? Hardy, temperate trees and shrubs are adapted to survive for up to several hundred years over many different winter intensities. If temperatures hold steady above and/or around freezing and gradually change, there may be no effects at all. However, when we get warm temperatures, greater than 50°F and/or fluctuations from very low to very high and vise versa in a short period of time, there can be problems.
High Temps in Winter, like we had in December, causes some plants to prematurely ‘wake up’ from dormancy and pop out spring flowers. There are some consequences for that come spring such as a later, longer and uneven flower display, reduced energy for growth, resisting pests and adverse environmental conditions (such as drought). This also can affect fruit trees that require adequate chilling hours like apples and pears, resulting in less, smaller, and/or misshapen fruits. Lastly, some pests are suppressed by the cold and without low enough temperatures, they have more opportunity to be active.
Wide, Rapid Fluctuations in temperature don’t allow enough time for plants to re-enter dormancy from which they can endure harsh winter conditions. This abruptness can result in stem cracking, sun scald and twig and bud death from starting to grow during a warm period and then quickly freezing.