Tip Top Trees: Winter tree pruning tips
Yes, you read correctly: winter tree pruning. I know, I know… it’s cold outside and you thought the outdoor chores were finished until spring. But it is the perfect time to give your trees some much-needed attention. So read on, sharpen your tools, and get to work. (Just don’t forget your gloves!)
Why winter?
Tom Kershner demonstrates proper pruning technique. Photo: Kirsten Werner
“There are several good reasons to prune a deciduous tree in winter,” says Tom Kershner, tree management coordinator for Natural Lands. “For one thing, without foliage, the tree’s branching structure is clearly visible, so you can make better, safer cuts.”
Other compelling reasons include the following:
- The tree is dormant, which means it won’t “bleed” sap from fresh cuts. (There are some exceptions to this, so read on.)
- Smart pruning can help a tree better withstand the effects of snow, wind, and ice that can snap branches.
- Winter pruning will result in a vigorous burst of new growth in the spring.
Though winter pruning is a good idea for most deciduous trees, oak species in particular should only be pruned then. Freshly cut oak emits an odor that attracts certain beetle species to the wound sites. These insects can carry with them fungal spores from trees afflicted with oak wilt, a serious disease that often kills infected trees. The beetles are hibernating during winter.
There are several other varieties of tress that are less likely to contract diseases when pruned during the winter months. Prune locust to prevent stem canker. Prune apple, crabapple, mountain ash, and hawthorn to avoid fire blight.
Dos and Don’ts
- DO cut at an angle that mirrors the branch collar—the furrow of bark where branch and trunk meet. “Trees don’t heal, they seal, says Kershner. “A healthy tree will respond to a clean, well-placed cut by forming a callus around the cut.” The callus will eventually cover the cut, creating a protective barrier to disease.
- DO cut large branches in three parts. First, cut off about one-third of the branch to reduce the weight. Next, undercut the remaining stub so the trunk bark won’t rip when the stub falls free. Last, make the final cut from the top, beside (but not cutting into) the branch collar.
- DON’T leave stubs behind. Instead, make clean, smooth cuts.
- DON’T top your trees. A tree with a flat-top looks ugly, and it will grow weak, new shoots in place of healthy branches. Cut to the tree’s natural shape and let it mature gracefully.
Tools of the Trade
Photo: Kirsten Werner
To avoid damage to your trees, make sure your tools are in good working order and the blades are sharp.
- Hand pruners are generally used to remove branches up to the size of your ring finger.
- Loppers are a better choice for branches of about two to three inches in diameter.
- Pruning saws are specialized saws with widely spaced teeth. They can handle branches up to about eight inches in diameter.
When you are finished your pruning project, take the time to clean your tools. You may even wish to rinse them in a 10-percent bleach solution to prevent spreading of any diseases. Before putting them away, be sure to the tool blades are dry to avoid rust.
Exceptions to Every Rule
Your elementary school English teacher was right: there are, indeed, exceptions to every rule and Mother Nature has a few.
- Much like the veins in our body, the tree’s vascular system transports sap, a sugary liquid filled with water and nutrients, throughout the tree via the phloem and xylem. If a cut is made in the trunk, the sap may start oozing out. Maple, horse chestnut, birch, and walnut trees all bleed extensively, even towards the end of their dormant season, so prune these species in mid-summer after new growth has matured.
- Trees and shrubs that bloom in early spring should be pruned immediately after their blooms fade. Some examples of these are chokeberry, flowering cherry, serviceberry, and deciduous flowering magnolia.
- Most conifers grow in such a way that they require little or no regular pruning. Occasionally you may need to remove damaged or distorted growth; this is best done in late summer.
Take a look at Tom demonstrating the proper, three-part pruning method in this brief video: