Types of Injuries to Trees in the Winter

  • Temperature fluctuations – once temperatures begin a steady decline in winter, trees start to acclimate. However, if there is a sudden hard freeze, plants can be greatly stressed if they are not fully acclimated. Woody plants in particular can be damaged in times of rapid temperature drops followed by periods of mild weather. The main reason is that during mild weather, trees de-acclimate and become especially vulnerable in case of temperature drops.
  • Low temperatures – while it is true that trees are perhaps the sturdiest species of the plant kingdom, they are far from indestructible. Every tree has a temperature tolerance level, which is sometimes exceeded. Trees that are already stressed by temperature fluctuations or those that are already marginally hardy for the area they are planted in are particularly vulnerable. If you are using marginally hardy plants, you may have to plant them in protected areas, or else they may not survive the season.
  • Cracks from frost – frost cracks, also referred to as radial shakes, take the form of deep and shallow longitudinal cracks in the area of the trunk. During the day cycle, the south and southwest side of trees experience the most stress in winter, and therefore are more likely to suffer damage. Sudden drops in temperatures cause the outer tree layer to contract more rapidly than the inner layer, as the latter comes in delayed contact with freezing temperatures. This is what causes frost cracks, which are likely to appear every year. Tree surveys reveal that London plane oak is particularly vulnerable to frost cracks.
  • Sunscald – de-acclimation of trunk tissue is the main reason of sunscald. It takes the form of elongated cankers on trees with thin bark. It occurs as one side of the tree gets exposed to direct sun, resulting in darkened and red-brown bark, which eventually cracks and falls away.
  • Spring freeze – freezing temperatures occurring as spring growth starts can be quite devastating to de-acclimated trees. Most vulnerable parts of the plant include new shoots, woody stems and blossoms. The symptoms resemble blight disease, but they appear suddenly, unlike most diseases, which take some time to develop.