Cold damage to ornamental plants can be a problem during the winter months. Plants prepare themselves for winter through a process called cold acclimation. This process is initiated by cooler temperatures and shorter day lengths that naturally occur at this time of year. Homeowners can take steps to help acclimate plants to cold temperatures and to protect plantsfrom temp extremes.
The timing of acclimation is very important. If acclimation occurs too early in the year the growing season of the plant will be shortened and if too late and a quick freeze occurs it can severely injure or even kill the plant. Cold damage can occur on all parts of the plant including fruit, stems, leaves, trunk and roots. Ways homeowners can prevent plants from injury starts with plant selection. Selecting plants that can tolerate average cold temperatures for your area will prevent them from being exposed to temperatures that are unhealthy and can cause damage. Then select the proper site. Site selection is key in protecting your plant with less work and worry on the caretaker. During the winter the coldest spots are often found on the north and northwest partof the property and in low areas where cooler air settles. The warmest areas will be found in the southern portion of the property and near larger plants and structures. Windbreaks such as fences and buildings will also provideprotection from cold winds which can damage plants.
Other practices a homeowner can provide is pruning during the right time of season. Avoid pruning in the late summer and early fall which will alter plant hormones and result in vegetative growth that is more susceptible to cold injury. Providing proper nutrients to the plant will also help during the winter months. Plants given appropriate nutrition are healthier and will tolerate cold temperatures better and recover quicker from injury. Also do not fertilize in the late fall as unseasonably warm temps can create a flush of vegetation that is more susceptible to cold injury.
Protect plants in containers by placing them inside a protective structure such as a house, garage, greenhouse, or shed. Since the roots of container plants are above ground they are especially sensitive to cold temps. Also plants in containers that are left outside should be bunched together and covered with mulch or burlap to reduce heat loss from the sides of the containers. Covering your plants with blankets or boxes will help protect them, but remember to remove the cover and provide ventilation during the day to allow heat to release that was trapped underneath. If the blanket is not removed this heat can cause growth activity to begin in the plant which would be very harmful when the plant is exposed to cold temps. Also continue to water plants regularly during the winter months. Moist soil absorbs more heat and will help maintain a warmer temp around the plants roots. Adding fresh mulch to the base of landscape plants and containers will also help retain moisture.
To determine if your plants have been damaged by cold, wait several days after a freeze and remove a portion of the buds, stems, or leaves and cut a cross section into the tissue and look for any brown or black discoloration.If localized damage is found in the foliage or stems you should prune out the damaged tissue several inches below the injured area. Some plants that are injured will recover on their own depending on the severity of damage,other plants may die and need to be replaced the following year.
Mallory Kelley, Home Grounds REA
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