Wrapping your trees to protect against winter cold sounds like a good idea, but it probably isn’t.
For decades (centuries?) people have wrapped their trees to protect against frost cracks, winter sunscald, and other forms of cold weather damage. While this sounds like a great idea, it ends up that those wraps can actually cause more harm than good.
The theory behind tree wraps
Winter tree and plant damage can occur in several ways: flat out freezing; temporary warming, followed by freezing; and cracks caused by the water within the plant freezing, expanding, and pushing its way out. When you get down to it, it is rapidly fluctuating temperatures that cause the most damage to trees in winter.
Types of tree wraps
Tree wraps, also known as tree guards, or tree liners, can take many forms. Commercially available tree wraps include white plastic guards, white adhesive tape, foil-backed fiberglass panels, capillary mats, landscape fabric, reflective greenhouse insulation, and watering bags. DIY growers have used paper, bubble wrap, burlap, cardboard, shredded newspaper, foam, and I have a neighbor who knitted sleeves for her trees!
It's very colorful, and I like to think that the good airflow allows moisture to evaporate enough to keep the trees healthy.
Some people make their own tree wraps by creating a tube of chicken wire fencing around the trunk and filling the space in-between with shredded leaves. All of these methods require frequent inspections to avoid becoming problematic.
Problems with tree wraps
According to the International Society of Arboriculture (ISA), studies have shown that tree wraps do not actually prevent temperature fluctuations. In some cases, temperature variations are even worse with the wraps. Also, tree wraps provide protection for many wood-boring insects, wasps, and earwigs, just to name a few. This is especially true with snugly fitting wraps.
Manufacturers and many gardening sites suggest that tree tubes be left on young trees for several years, until they are well established. They claim that tree tubes insulate the trunk against winter sunscald and shade it against summer sunburn. These tubes may also prevent a tree from swaying in the breeze so much that it fails to get strong, through a process called thigmomorphogenesis. [How’s that for a cool garden word?]
Wrapped too tightly, tree wraps can interfere with normal growth, causing girdling. Depending on the material used, it may cut into the bark, causing points of entry for pests and disease.
Often bare root stock and young trees are sold with tree wraps in place. These wraps can provide protection during digging and shipping, but they can also hide injuries, insects, and improper pruning.
Wrapping your trees may reduce mechanical damage and rodent feeding, but it is more likely to result in insect damage and fungal disease. And it will not protect your trees against frost cracks or winter sunscald. Personally, I prefer whitewashing, mulch, and proper irrigation to prevent cold weather damage.
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