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The Journal Gazette

Saturday, January 13, 2018 1:00 am

Cold snap can hurt plants in our area

Ricky Kemery

Question: Will this extremely cold weather damage plants growing in our area? Will it reduce the number of insects that will be out and about next year?

Answer: Even though we have experienced some cold weather recently in our area, the trend and predictions for our winter are generally slightly warmer than normal. I have found over the year that several factors come into play when it comes to winter damage to plants.

The first factor is the plant itself, and how cold hardy the plant is. Even though we are listed in USDA Zone 6, it is probably more prudent to still think Zone 5 when it comes to our area. Some plants listed as hardy to Zone 6 can take a real hit when temperatures dive down in the subzero range. There isn't much one can do to protect those plants either. If the plant is only cold hardy to minus 10 degrees, and it dips to minus 15 during the winter, the plant is probably toast.

Another factor that relates to cold damage is the wind. The brutally cold winds we have experienced can draw moisture out of plants, especially evergreen plants. It is always a good idea to wrap exposed boxwood, holly, dwarf spruce, rhododendron and arborvitae to prevent damage to the foliage. Otherwise the plant can exhibit what I refer to as brownchitus – browning or death to the foliage caused by the wind.

It is also a good idea to protect lace cap and mop head hydrangeas from the cold. These plants can dieback to the ground during severe winters if not protected.

One might as well expect the foliage on many shrub roses to suffer from the cold. I have noticed that these roses tend not to harden off well as the winter approaches. This means these plants will most likely once again take a hit with dead foliage appearing in the spring. Wait to see how much of the plant is damaged, and prune away the dead foliage. These plants often recover quite nicely as the spring progresses.

The flower buds of hydrangeas are sensitive to late spring frosts and freezes – another reason to wrap those plants. Cut-leaf Japanese maples are especially sensitive to cold snaps and wind during the spring. Put a wind barrier made of cardboard or burlap to help protect them.

Some fruit plants, especially peaches, can be greatly affected by cold. It is one reason why peaches are not a particularly reliable crop to grow in northern Indiana.

I have generally found that insects are remarkable at withstanding cold temperatures. Insects seem to innately know not to be fooled by warm spells in the spring. So for the most part, insect development can be delayed by the weather, but I have not seen rampant death of insects due to cold weather in our area.

Cold winter weather can cause damage to particular plants. One can only wait for the warmth of spring to find out how much damage occurred.

The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery retired as the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.