Winter Pruning Advice

So far it’s been an incredible winter if you’ve wanted to work outdoors.

We’ve had many nights that have been cold enough to harden off most of our plants, and with mild days there’s no excuse for not getting out and taking care of the winter pruning. Ah, but the annual question, what to prune in the winter and why?

Winter pruning is also referred to as “dormant pruning.” It’s done at this time of the year when we want to shape and control shrub and tree growth as well as to encourage fruiting, flowering and new shoot growth on some other plants. It’s a time when pruning is not subject to disease issues, the cuts we make won’t attract insects and there’s no foliage in the way to block our view when aesthetic pruning is done.

But this is not the time for pruning everything. Spring flowering shrubs, like forsythia and magnolias, need to be left alone, also hydrangeas, that you know will flower only on the previous year’s growth.

It’s also not the time to prune what we call “bleeders,” such as elms, birch, walnut, hornbeams and others. These trees tend to bleed sap when pruned in the colder months; and while this worrisome hemorrhaging can be troubling (though not fatal), we tend to hold off pruning these trees until the foliage has emerged in late spring.

Research has shown that the larger the cut made to a limb or branch, the longer it takes that limb or branch to become desensitized to the cold. But that process takes only about 10 days. So if you’re in doubt about your timing, take a look at the long-range weather forecast and if there isn’t a sharp and sudden dip in the temperatures forecast for the 10-day period after your pruning, then your work is probably safe.

Constantly moderate cold temperatures are not a problem when it comes to dormant pruning. But if it’s 35 to 40 degrees on the days you’re pruning and then it plunges down to the single digits a few days later, you’ve not planned properly.

There are also safety issues to consider. Using a ladder on frozen ground can be tricky, especially if the sod is soft and the underlying soil is frozen. This can lead to a banana-peel condition where the frozen soil allows heavy objects (you and your ladder) to slide across the softer top layer of sod. Frozen soil can also make it hard to stabilize a ladder, possibly throwing you off balance.

It is essential to make proper cuts when pruning trees. Do not make flush cuts. Flush cuts are cuts made as close as possible to the trunk or main branch. Flush cuts produce large wounds, destroy the tree’s natural mechanisms that promote healing and slow the healing process.

When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk.

Pruning just beyond the branch collar and branch bark ridge retains the tree’s natural defense mechanisms and promotes the healing process. When a branch is pruned properly, a slightly raised area remains on the trunk or main branch. However, don’t leave stubs.

Use the three-cut procedure when cutting large branches to prevent extensive bark damage. Make the first cut about one to two feet from the main branch or trunk. Cut upward and go about halfway through the branch. Make the second cut a few inches beyond the first. Cut downward completely through the branch. Make the final cut just beyond the branch collar.

We no longer apply “paints” and wound dressings to our pruning cuts. The application of wound dressings or paints doesn’t stop decay and may actually inhibit or delay the healing of wounds. There is one exception: oak trees—but only when they are pruned after April—to prevent attracting beetles that carry wilt infections.

Larger cuts than can’t be handled with a hand pruner or lopper should be done with a special tree pruning saw. These are available at most garden centers, with blade lengths depending on the size of the cuts you will be making. These saws cost between $20 and $50.

Pruning roses often presents a dilemma to those not well versed in their care. The only roses that I like to prune in the winter are the climbers. Winter pruning of these roses allows me to reduce cane damage from wind and ice, as well as gives me an opportunity to redirect the growth pattern and reduce crowded areas to allow for better air circulation in the upcoming growing season.

In late winter, I’ll do a mass cut-back or reduction of most of the rugosa roses to encourage fullness. But for the rest of the roses, I like to wait until very late winter or even early spring to see if there’s any cane dieback, and then prune accordingly.

Butterfly bush,

buddlea devidii

, benefits from a hard pruning and tends to bloom on new wood. Pruning can be done during the winter if you have the opportunity.

This winter, butterfly bushes have been very reluctant to lose their foliage. The variety “Heaven,” introduced by Blooms several years ago, has not only retained its foliage but it’s turned a wonderful gray.

The somewhat woody butterfly bush stems are often hollow and can be cut down to about two feet, though more severe pruning does not harm them and results in a more vigorous plant come summer. Cuts can be made above the lowest swelling buds, which will result in other buds further down the stem being forced to send out growth as well. This usually results in multiple stems emerging from each old stem stub. If new growth is too heavy, additional thinning can be done early in the summer.

I’ve just scratched the surface on winter pruning, so to speak, but there are plenty of books and lots of free online resources if you need more guidance. Next week, back to the seeds, and some thoughts on the economics of growing your own vegetables. Keep growing.