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University of Idaho Extension Educator

You may have had the unlucky experience this spring of finding that one side of your pine trees has turned brown, while the rest of the tree has stayed green and looks good. If this change occurred over the winter, and last fall the tree was fine before winter started, then there is a good chance you have a mixture of damage due to wind desiccation and sunscald.

Evergreens, and specifically pines in this situation, are more prone to having these two issues together than other trees when they are young. As small trees they lack a large and established root system to be able to draw in enough water to keep the whole tree alive through the winter months.

You have to keep in mind that pines and all other evergreen trees, like spruce or fir trees, actually do not go dormant like deciduous trees during winter. Instead they just “slow down” their natural processes of drawing in water through their roots and are technically still functioning, and completing their natural plant processes. So since they are pulling in water throughout the winter and we live in such a dry arid climate, and we have drying winds throughout the winter time then one side of our trees will often times die back.

To compound this issue, we also have sunscald that can occur during February and March when there is still snow on the ground, and happen to have days where the daytime temperature spikes and the nighttime temperature drops to well below freezing. This can cause the fluids in the bark or needles on the side of the tree that gets the most sun to freeze during the bitter cold of night, damage the plant cells during the freezing process, and kill off that side of the tree.

It technically could be a mixture (or one of the two) of wind desiccation on the needles and also sunscald depending on the type of tree, location, snow depth around the tree and other factors.

So, what can we do to help prevent these two issues from damaging our trees?

To help prevent wind desiccation on young pine trees, you will want to protect them from constant winds by putting up a windbreak, (at least during the winter, and while they are young). Next you want to make sure they are well watered at the end of the growing season and that they go into the winter season well irrigated. This may entail irrigating them with a hose and sprinkler weekly until mid-November depending upon weather and temperatures.

The other thing you can do is buy smaller evergreen trees to start out with, rather than larger ones since the ratio of root system size is more in balance than a larger tree with a small root system. To manage sunscald on evergreen trees there aren’t many options, aside from wrapping them in burlap during the winter to prevent temperature fluctuations in the needles or bark. Wrapping them in burlap can also help to stop the wind from drying them out and experience needle desiccation.

For further questions, please call Lance at 208-624-3102