When It's Time To Cut Your Losses And Prune Winter-Damaged Plants

Cold winters take a toll on plants. Know when it's time to prune.

This hydrangea will rise again! Photo: Ellen Grooms. Photo: Photo: Ellen Grooms

Even if described as "cold-hardy," frost and below-freezing temperatures can damage your previously thriving plants. The key to saving these plants is knowing when to prune. Pruning frost-damaged plants too soon can prevent future growth, so even though you might not like the appearance of those browning leaves, keeping them in place can be beneficial.

However, if hope springs eternal in the garden, what happens to your shrub or tree that remains bare? Did it forget spring is almost over, or did it skip a year of growth? No, but this might be a sign to cut your losses and prune your damaged plant.

As with many cold winters, it takes a toll on plants. Broadleaf evergreens like gardenia, loropetalum, and creeping fig can show the first sign of apparent damage during winter. This damage looks like brown, toasty foliage instead of lush green leaves. Grumpy notes that sometimes numerous deciduous plants should be leafing out in spring but, for some reason, haven't yet. So, what's happening with these plants? Here's what you need to know about frost-damaged plants and how to know when it's time to prune.

The Difference Between Frosts and Freezes

Both frost and freeze signify a drop in temperature, but there is technically a difference between these two cold-weather phrases. Frost temperatures range from below 36°F to above 32°F—the freezing point. Temperatures below the 32°F freezing point will likely cause frost damage and plant injury.

Some cold-hardy plants can survive temperature drops when a light layer of frost (or water vapor) freezes on the plant's surface. Sustained low and freezing temperatures increase the likelihood that a plant's interior and exterior water sources will freeze, killing the plant.

When Not To Prune

You might not like to look for frost damage, but for cold-hardy plants, the color changes in leaves and plant structure can signify dormancy. Gradually exposing plants to colder weather or high winds can help ease the transition into dormancy, so a plant is not shocked by changing temperatures.

Wait to prune brown leaves until you are sure there will not be any new growth. The "dead branch" might produce leaves again, and pruning will effectively stop this from happening. Until damage occurs to the plant's interior, the exterior browning and leaflessness can be a method of protection. Even if your plant appears finished blooming or leafing for the season, be sure to check the base or roots underneath to see if new, green growth is present.

For example, many French hydrangeas (Hydrangea macrophylla), like the one above owned by faithful reader Ellen Grooms, either were a total mass of naked brown stems or looked dead at the top with only green shoots coming up from the bottom. Grumpy hears similar complaints about crepe myrtles and Japanese maples (especially from people in the Upper South and parts of the North), as well as pomegranate andfig trees.

When To Prune: Spotting Damaged Plants

Despite your best efforts, there will still come a time when pruning is necessary. If your plant suddenly wilts, leaves turn brown overnight, or the plant turns crispy or even black, this plant is most likely frost-damaged and finished for the season. Wait until the final frost in your area to prune frost-damaged plants. Ensure that the cold weather has passed for the season because early pruning can prevent the new season's growth from occurring, as pruning stimulates new growth. Early pruning can also remove branches that are still alive, so waiting until the new season's development will help distinguish between dead and dormant.

Branches leaf out in spring. If they do not leaf out in spring, they are dead. Branches don't skip a year in leafing out—no matter what you've heard elsewhere. So get out the loppers and pruners this weekend and cut off the dead branches. Leave alone any growth coming up from the bottom of a hydrangea because if your hydrangea happens to be a reblooming type, like 'Endless Summer' or 'All Summer Beauty,' it will still bloom in the upcoming season. If not, you'll have to wait until next year for blooms. Also, you can test a plant's viability by lightly bending a branch because its flexibility signifies life, while a clean break or snap usually means it is a dead branch.

As for crepe myrtle, pomegranate, and fig, cut off all dead branches. If a trunk is dead, cut it to the ground. Luckily, these plants all flower and fruit on new growth. Cut off the dead branches from Japanese maples, too. They'll all grow back quickly to regain their former glory—just in time for the next winter's big freeze.

When To Prune Frost-Damaged Plants

First, wait until the spring to prune. For plants that will remain outdoors throughout the winter or cold season, do not remove the leaves or branches, as these protect the plant's interior.

When pruning plants in the spring, remove dead branches or stems entirely. (Be sure to leave healthy components). If severely frost-damaged, pruning to stimulate new growth might require cutting a plant back to the ground. Leave a few inches of the plant as the base is less susceptible to injury.

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