You have likely lost a few plants to low temperatures. Here are some symptoms of cold-damage and some strategies for helping plants survive the cold.
DIEBACK – Dieback is caused by severe cold and rapid changes in temperature. Woody plants, like privet, survive, but only the bottom part of the plant will leaf out in spring. The roots are hardy and the lower portion of the plant was likely protected by snow cover or leaf litter. Bud blast is similar to dieback, but the cold kills the flower buds of early spring-blooming plants. This is common in our area with forsythia, hydrangea and rhododendron. For plants that are susceptible to dieback or bud blast, try insulating them from the cold by making a circle of fencing around the plant and filling it with straw or dried leaves. Or choose new plant varieties that can withstand cold temperatures without suffering damage.
FROST HEAVE – Tap-rooted perennials, such as coral bells, are most susceptible to frost heaving. Other affected plants are Shasta daisies, blanket flower, garden mums and coreopsis. Alternating freezing and thawing near the soil surface pushes plant roots out of the soil. Tamp the soil back down or the roots will dry out and the plant will die. For plants that are susceptible to heaving, place an extra layer of mulch on top just after the ground freezes. You can also weigh them down with a brick.
CRACKED BARK – If you have newly-planted trees, their thin bark is susceptible to freezing and thawing cracks. This occurs when the bark expands as it warms during the day. Usually the southwest side of the bark warms the fastest and damage is most commonly seen on that side. When the sun sets and the temperature drops, the outer layer cools and contracts faster than other portions, resulting in vertical cracking. These cracks can later be colonized by decay fungi, or serve as an entry point for various borer insects.
Often the tree is able to heal the crack. The tree should begin to form a callus or thickened area around the split. You will want to watch that area closely for signs of insect damage or disease. If the wound stays wet and starts leaking (especially if the leakage is black), that's a sign of infection. Then is the time to call a tree expert to have a look. Do not paint or cover the area.
Avoid fertilizing trees in the late fall, as that encourages new growth and new growth is more susceptible to splitting. Thin barked trees such as maple and cherry are more prone to frost cracking. To prevent split bark, wrap the trunk with a light-colored material, such as pellon or purchase a white tree guard. Be sure to remove it in the spring so it won’t harbor insects or fungus.
If you have other questions about your garden or landscape, feel free to contact a master gardener at the University of Illinois Extension office in Charleston at 217-345-7034. You can also check out the many horticulture webpages at the U of I Extension’s website by visiting http://web.extension.illinois.edu/ccdms/ . And be sure to like the Master Gardeners’ Facebook page, at www.facebook.com/ColesCountyMasterGardeners.
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If you have other questions about your garden or landscape, feel free to contact a Master Gardener volunteer at the University of Illinois Extension office in Charleston at 217-345-7034. You can also check out the many horticulture webpages at the U of I Extension’s website by visiting http://web.extension.illinois.edu/ccdms/ . And be sure to like the Master Gardeners’ Facebook page, at www.facebook.com/ColesCountyMasterGardeners.