Over the Garden Fence | Protect your outdoor plants from Old Man Winter

For the CDTNovember 9, 2013 

We are still enjoying the relatively mild fall weather in most parts of the state, unlike some other parts of the country, but my calendar continues to march toward more harsh winter weather.

While the days are still relatively pleasant, take a look at the parts of your landscape that might need some winter protection before the weather turns bitter cold.

It’s much easier to build a section of snow fence now, before the soil freezes and the winds blow.

Extremely low temperatures can kill some plants. Similar injury can occur to marginally hardy plants that are able to survive mild winters until their limits are exceeded in one very cold period.

Warmer weather may have serious implications for some plants that are tricked into thinking winter has come and gone. A good example of this is forsythia, viburnum, spirea and flowering cherry, which will sometimes have a few flowers open and other flower buds beginning to open. These buds are the flowers that should be opening next spring. If this occurs, we can enjoy the limited flower color now, but I suspect these plants will flower weakly next spring.

Plants that have retained their seasonal dormancy into the winter can have other problems. Winter drying can be a serious factor in extended periods of very low temperatures and blowing winds. Even the best of plants may be dried to the point of permanent injury under these conditions. Plants set in windy locations, especially newly planted materials, should be protected. Wind barriers placed in front of these materials will help prevent wind burn and dehydration.

A common wind barrier is the snow fence, used alone or covered with burlap or plastic to increase its effectiveness. Stakes and burlap also will afford a good degree of protection from the wind.

Under no circumstances should you put plants in an airtight enclosure. For example, do not cover plants with a large plastic trash bag that will indeed keep the wind out but on a sunny day allow temperatures inside the bag to be high enough to literally cook the plant.

Most available forms of winter protection reduce water loss from the plant. Snow fences, tree wraps and anti-desiccant spray slow the movement of water from trunks and leaves. Craft paper and burlap protect thin-barked or newly set trees from excess water loss in the trunk. Wraps also reduce damaging temperature fluctuations in the bark.

Many gardeners fail to realize that roots also can dry out over the winter. Shallow-rooted plants like rhododendron and azalea frequently survive the cold only to die the next spring because of a dry root system. When roots dry completely, they don’t supply water to the stems and leaves. This is often the case when a plant leafs out in the spring only to collapse and die in a few days from a dead root system.

To reduce injury to the root system, use about a 2-inch layer of mulch under your plants, but don’t put it on until the ground freezes hard. Mulch also will prevent the alternate freezing and thawing of the soil, which injures many roots in the spring. Be sure to keep the mulch material away from the plant’s stem to eliminate a hiding place for mice that might feed on the plant’s bark and create a whole new set of problems.

Large spreading plants may need support against heavy snow loads later this winter. Now is an excellent time to get materials on hand and even put them in place before any damage occurs.

Winter protection completed in the fall is well-worth the effort because it prevents the work and cost required to replace plants in the spring.

Bill Lamont is a professor and extension vegetable specialist in the Department of Plant Science at Penn State University and can be reached by email at wlamont@psu.edu.

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