If the damage is severe enough, sunburn kills the bark causing necrosis-the death of cells or tissue. However, we do come across sunburn in trees when the sun causes serious damage to the bark of the trunk or branches. Short term temperature differences in Australia aren't usually as extreme, so this sort of sunscald rarely occurs here. The cells in the bark of the trunk or branches have become active during the warm day, and are then badly damaged as they rupture during the cold night.ĭamage can be extensive, or even fatal, for some young trees and is nearly always greatest on the south and southwest facing tissue. In the northern hemisphere, sunscald usually occurs towards the end of winter, when a warm day is followed by a freezing night. When dealing with trees, sunburn is also referred to as "sunscald"-which is unfortunate as there are two different processes at work, but even scientists often use the terms sunburn and sunscald interchangeably. This damages the cells' metabolic processes and limits the ability to photosynthesise in a process called "photoinhibition." If enough cells are damaged, you can get general brown or dead leaf tissue. However, it's possible and perhaps likely very high levels of radiation increase temperatures within some of the leaf cells. So what does cause leaf scorch? Well, we're not sure. There is little evidence it occurs and considerable evidence that it doesn't. One popular and widely published cause of sun scorch on leaves is water droplets on the surface acting as a lens that focuses the sun's rays and intensifies the heat-a bit like a magnifying glass. The damage is often exacerbated by a low level of soil moisture, which reduces the cooling effect of transpiration (when water evaporates from leaves). Leaf scorch can occur because leaves are exposed to high levels of solar radiation. This is sun damage, but is not the same as sunburn on trees. Many of you may be thinking of sun scorch, which occurs on the leaves of some of our favorite garden plants on a hot summer's day: the brown, wilted hydrangea leaves or the large blotchy brown patches that appear on camellia leaves that weren't there at the beginning of the day. So let's explore why it happens, and the easy ways you can protect your trees from damage. Tree sunburn tends to occur during hot spring days or in early summer, when trees are full of moisture. Some pets, such as cats and dogs, can get sunburnt in some of their less furry places, and pig farmers have long known the damage sun can do to their prized stock.īut have you ever wondered about sun damage to plants? Can trees be sunburnt? It may surprise you to know the answer is actually yes! It's not only humans that suffer from sunburn and its consequences.
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