Winter Sunscald in Trees
As we head into the season where many of us wrap gifts I have another gift wrapping suggestion….wrap your trees. Well at least wrap the trunks of your young and thin barked species. This could be a crucial gift to many of your trees.
You are probably wondering what on earth I am talking about. Let me explain… When we are cold even the slightest warm touch of the sun is noticeable on our skin, too long and we get a sunburn. It is the same for trees, but they cannot cover up or move so they can succumb to sun scalding and overwarming. This is called Southwest Disease or Sunscald. Just go out a look at some of the young maples and dogwoods planted in nearby commercial landscapes. You may notice long wounds running up and down the south west side of the trunk. There is usually little shade in new landscapes and these trees that typically grow in woodlands are exposed to a lot of sun. What happens is that the sun warms and thaws the vascular system on the south and west sides of the tree even though the air temperature is below freezing. The dormant cells become active and when the sun goes down or we have sudden temperature drops the tree cannot react quickly enough and the vascular system that has thawed can freeze and the cells burst resulting in massive tissue damage that appears as cracks, sunken areas and open wounds. Not only is this unsightly but it can dramatically affect the health of the tree. Probably the biggest impact is that the damage opens the tree to invasion by other pests and diseases.
Some of the common trees typically affected are Maples, Ash, Tuliptree, Dogwood, Cherry, Honeylocust, Willow, Birch, Crabapples, Cottonwood, Linden and even young Oaks. Many of these trees become less susceptible as their bark matures but some like the cherry have dark thin bark that can become more susceptible as they age and there is more surface area that warms in the sun.
What we can do is wrap the young tree trunks in tree wrap. Most garden centers or nurseries carry tree wrap. I just purchased some from Rolling Ridge in Kirkwood. The wrap is usually a paper or thin plastic that is easy to apply. You leave it on through the last freeze of the winter. This helps insulate and reflect away the heat of the sun. As these trees age they develop thicker bark with deeper furrows and ridges that naturally protect the vascular system so they are less susceptible and no longer need wrap. So remember, many of these trees have been planted in spots very different from where they evolved to thrive so we have to take measures to insure they can thrive and survive.