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Got Winterburn?

With the unusually cold winter this year, you may have noticed more winter-burn on your broadleaved evergreens and evergreen perennials than you might normally see.

Winter damage appears as drying along the edges of the leaves, the entire leaf, the death of the younger shoots, or even the entire plant.

The damage occurs when the evergreen plant is losing water through its leaves faster than it can replace it from the soil. During the winter, this occurs when the weather is cold and windy, the ground is frozen, and the plant is unable to take up water.

When the weather is warmer, the plant takes up water through the roots so that the leaves are better able to sustain water loss. If the soil is dry and the plant can’t take up water during warmer periods, then the damage is more severe.

How do you prevent winter damage? Water broadleaved evergreens in the fall during dry spells, especially those that are newly-planted.  You may need to water once or twice during the winter when the ground is thawed, more regularly if the plants are in containers. Particularly sensitive plants such as camellias should be planted in sheltered locations, out of the wind.

What to do now?
Give the plants a good soaking—water thoroughly.  Let the damaged leaves drop; they will be replaced by fresh leaves soon. For evergreen perennials such as hellebores or epimedium, remove the old damaged leaves and stems, taking care not to cut off the newly emerging leaves and/or flowers.

If entire shoots looks dead, scratch the stem with your fingernail. If it is green beneath the bark, it is still alive and may send out new leaves. If it looks dry beneath the bark, like a toothpick, then the shoot is probably dead. Regardless, wait a few weeks to see where new growth emerges before you prune out dead shoots, or pull out the plant. Unless you are an experienced gardener, it’s best to wait until mid-or the end of April before pronouncing the patient dead.

Feel free to cut off a couple of shoots about 6 inches long with some damaged leaves and bring it into the store. We will be happy to look at it for you and tell you whether we think your damage is caused by cold or some other factor.

by Larry Hurley

Photo thanks to the Missouri Botanical Garden.

Larry Hurley, perennials specialist for Behnke Nurseries (now retired), started with Behnke’s in1984. Larry enjoys travel, food and photography. He and his wife Carolyn have visited Australia, New Zealand, Thailand, Brazil, South Korea and much of Europe. Their home is on a shady lot where a lot of perennials have met their Maker over the years.

This Post Has 2 Comments

  1. We have young pine tree saplings we are trying to try our hand at Bonsai’s I think they are sun burnt how do I tell whether they are dead? branches and trunks still bending when I broke a branch off it was still green but every needle is brown 🙁 Help lol
    Thanks for any help if you can give it

  2. Denise,

    Conifers like pines that have damaged growth may replace needles more slowly than broadleaf plants because they can’t regrow as many needles along the whole branch the way the broadleafs usually can. That means it may take more than a year or two for a lot of needles to be completely replaced (which is more likely in a young plant such as yours than in older plants). Wait for the damaged foliage to drop naturally, then see what new growth emerges; like Larry says, this should be evident by the end of April. Poor new growth may mean there was too much cold damage for complete recovery. Normally I’d say to fertilize to encourage vigorous new growth, but bonsai are fertilized sparingly and vigorous growth is usually not the intended result. If these plants were kept in pots, as most bonsai are, keep in mind that the smaller the container, the more vulnerable the root mass will be to temperature extremes and dessication, especially causing winter burn and summer drought stress.

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