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Cold weather damage to trees

02/27/03 12:00AM By Charlie Nardozzi
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(Host) Commentator Charlie Nardozzi has some advice for recognizing and dealing with cold weather damage to trees and shrubs.

(Nardozzi) It some areas of Vermont the thermometer has been dipping to below 30 degrees F. If you think it's cold for you and me bundled up in our well insulated coats, hats, and mittens, imagine being a shrub or tree with your bare bark exposed to those extreme temperatures.

While native trees and shrubs are adapted to Vermont winters and can take the cold, there are many non-natives that have been planted over the last few relatively balmy years. Those mild winters have given gardeners a false sense of security. I believe this winter is going to shake us back into reality.

Before you panic and start searching catalogs and the internet for the hardiest replacement plants you can find, let's take a look at the signs of cold weather damage.

The shrubs that are most likely to suffer are those that are marginally hardy in Vermont. Most of Vermont is rated to USDA zone 3 or 4. USDA zone 5 varieties of shrubs such as evergreen holly, rhododendron, boxwood, and even burning bushes are the ones you may see damage on this spring. It's hard to tell in the middle of winter if your shrub will survive, so don't panic. Wait until spring, when the buds swell, to assess the damage. Winter injured shrubs may leaf out later than other shrubs. Also, not all of the shrub may be injured. If part of the shrub was covered in snow, it probably survived just fine. The classic example of the insulating effects of snow is on forsythias. I predict this spring well see many half blooming forsythia shrubs. The branches that were under snow will bloom beautifully, while branches exposed to the frigid air probably have many dead flower buds.

Some shrubs may appear to be killed, but still survive. I remember five or six years ago we had a real cold winter. There was this one burning bush in South Burlington that literally died to the ground. But the roots survived and regrew. Today, it is a majestic six-foot tall and just as wide shrub once again.

Trees have a different concern. The bright sun during those bitterly cold days really can warm up and expand the bark on the south side of a tree. However, once the sun sets and the temperatures plummet, the bark contracts, often splitting. I can remember a few nights lying in bed hearing trees snapping in the woods during one cold spell. The best safeguard is to white wash or wrap the bark so it doesn't heat up so quickly. If it already has cracked, wait until spring to assess the damage and do corrective pruning.

So even though its been a bitterly cold winter, its a good reminder of where we live. Global warming may be happening, but this winter gave us a taste of some real old fashioned, north country weather.

This is Charlie Nardozzi in Hinesburg.
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