A fresh coat of winter snow over the sleeping flower beds, or ice twinkling on the tree branches in the morning sun, can rival the beauty of a summer garden in full bloom. But those frosty scenes, as stunning as they may be, can also inflict serious damage on your trees, shrubs and other perennials. Below are some of the worst effects plants can expect from winter snow, ice, wind and frost, and some tips for preventing damage in the future.
1. Extremely Cold Temperatures
What it is:
Most trees and shrubs that are hardy for your region and well established before winter will stay dormant through the coldest months. The problem comes when the temperature bounces up and back down–a midwinter thaw followed by a return to winter cold or a cold snap in spring after new growth has begun.
Extended periods of sub-zero temperatures may cause evergreen foliage to yellow or brown, a condition known as leaf burn. Twigs on trees and shrubs that lose their leaves during winter can also be damaged or killed.
If a cold spell arrives after plants have begun to bud, new growth can be killed resulting in plants with fewer leaves, flowers and fruit. The damage may be unattractive, but plants typically recover through the growing season.
Sunscald and frost cracks can appear on even the healthiest trees. They occur when extreme temperature fluctuations cause water in the tree to expand and then contract. This damage usually happens on the south-facing side of a tree or in the weakened wood of existing wounds in the bark. Warmth during the day heats up the plant cells and they expand, but then a sharp cold shift at sunset doesn’t allow time for the bark to cool slowly. Instead, the cells contract quickly and snap causing a split in the bark.
Heaving results when water freezes and unfreezes in the ground causing the soil to shift and buckle. This movement caused by temperature extremes can sometimes uproot plants in the process. Perennial plants and newly planted trees or shrubs are particularly susceptible. Larger trees or shrubs can become loose, unstable and may start to tip out of the ground during strong winds.
Winds can also cause damage to broad-leaf evergreens and conifers in a process called desiccation. This is a condition caused when moisture is drawn out of the leaves. It occurs when the soil freezes and water is unavailable to replenish the moisture in the leaves. The result is yellow, brown or purple-tinged leaves that unfortunately don’t recover. New growth will eventually return, but the discolored foliage will remain.
New plantings may benefit from a wind break. Sensitive plants, like broadleaf evergreens, are best planted in a location protected from north or west winds. Locations along a fence or building provide added protection.
- The first winter after planting a tree or shrub, you can make a wind break using two or three stakes and burlap. Place the wall on the windward side of the plants. By the second winter you shouldn’t need to provide protection any longer.
- A regular schedule of fertilization helps keep plants strong and resilient to weather, pests and diseases. Stop fertilizing around the first of August so your plants can let their summer growth harden off before the cold begins.
- Frost cracks that develop on old bark wounds, can often be prevented by careful pruning and avoiding the wounds in the first place. Protect the base of trees from cracks or sunscald by applying whitewash (to reflect light away from the bark), or wrapping with burlap, paper tree wrap or cardboard. Remove wraps in the spring.
- Amend your soil each fall with a high-quality compost. This will help keep it draining well and reduce the threat of heaving.
- Make sure plants are well-watered through the growing season so they establish strong, deep root systems.
- Mulch perennials and newly planted trees in the fall to help reduce extreme changes in temperature around the roots.
2. Ice or Heavy Snow
What it is:
Heavy snow or ice can bend and snap tree limbs. Branches coated in ice can become brittle and break if they are subject to high winds, such as in an ice storm.
In extreme cases, when a smaller tree is bending under the weight of ice, you might be able to temporarily support it with a ladder or boards to keep it from breaking.
There’s nothing you can do about how much it snows or often the icy winds blow. You can, however, use a broom to gently knock snow accumulation off bushes and lower tree branches. Do not try to knock ice off, as you are likely to break the brittle branch rather than save it.
What it is:
Heavy snow cover makes it difficult for rabbits, mice, squirrels and other rodents to forage for food on the ground. They’ll chew through the bark of trunks and branches looking for the tasty green cambium layer underneath.
When a rodent chews his way around a trunk or branch, it’s called girdling and can kill everything above the damage.
You can fashion a tree guard with chicken wire to keep rodents away. Also clean up brush piles near susceptible trees to reduce habitat and consider creating a perch to attract birds of prey, who will be glad to help with rodent control.
4. Salt Damage
What it is:
Trucks applying deicing salt to the roads can spread salts up to 150 feet (45 m) onto lawns and into garden beds. Uninformed homeowners may add to the problem by using chemical deicers on their paths, driveways and sidewalks.
Salt can burn lawn grass and lead to leaf scorch on evergreens similar to that caused by extreme temperatures. Plant growth can become stunted if soil remains high in salts.
Add a gypsum conditioner to your lawn in spring to counteract the salts in the soil.
In spring rinse off plants that may have been exposed to salt. Once active growth starts, water heavily a couple of times to leach out salt accumulated in the soil. For every 6 inches (15 cm) of water applied it will leach approximately one-half of the salt down into the soil area below the root zone. Twenty inches (50 cm) or more of heavy spring rains will usually do the job naturally.
Use sand or kitty litter as an alternative to salt or chemicals to deice your paths and sidewalks. Deicing products are available that are safe for use around plants and pets. Salt, although inexpensive, is the worst possible choice since it can do the most damage to plants. When using deicers, start off using the least amount needed to get the job done. You can always apply more as needed. This approach saves money and reduces the amount of salts flowing into the soil.
What it is:
Just when you think your icy winter woes are over, spring can bring an unwelcome reminder of winter in the form of hail. Hail results from strong storms that push water droplets high up into the freezing temperatures of the upper atmosphere. The droplets grow larger layer by layer as water accumulates and freezes. A storm’s strong updraft will continue to keep the developing ice spheres suspended until they become too heavy. At that point the hail stones start to cascade to the ground.
Hail is most common from spring through fall, when the weather patterns are most favorable for creating hail stones. Spring hail storms can be the most damaging because many plants are emerging at that time. Young plants and tender new growth are easily crushed or broken. Hail can also break delicate stems and leave foliage torn and tattered looking.
It’s impossible to protect plants from hail because the appearance of a hail storm is so unpredictable. Following a storm, you will simply have to inspect your plants and decide if they can be salvaged, outgrow the damage, or need to be replaced. As always, broken branches on trees or shrubs should be trimmed or removed promptly.
There’s no denying it, the winter garden can be beautiful. But while you are enjoying a winter wonderland, under all that snow your landscape plants may be struggling with the blues. Help your plants stand up to winter. Make the right plant choices for your growing region and keep your trees, shrubs and perennials in good health.