Preventing Winter Damage to Trees, Shrubs and Roses
Protect your landscape this autumn
for healthy growth next spring
IF last winter's extreme weather took its toll on your landscape plants, you aren't alone. Last spring, gardeners nationwide discovered what a harsh winter can do to roses, trees and shrubs. The Old Farmer's Almanac predicts another hard winter ahead. Fortunately, you can take steps in autumn to prepare plants for what's coming.
Winter damage on an evergreen shrub
ShrubJackets protect against drying winds, as well as sunscald, salt spray and animal browsing.
Extreme cold isn't the only challenge faced by woody plants; in fact, plants hardy to your region should endure normal winter temperatures just fine. However, winter can wreak havoc in other ways.
- Early cold spells can damage plant tissues that haven't had a chance to harden off for the winter.
- Dry winds and winter sun can dry out or "burn" conifer needles and broadleaf evergreen foliage, which continue to transpire (give off water vapor) during winter.
- Frozen soil means plants can't take up water to replace the moisture lost from evaporation and transpiration.
- Midwinter thaws can "fool" plants into breaking dormancy too early, and the tender new growth may be killed by the next cold snap.
- Alternating freeze/thaw cycles can heave new plants out of the ground, leaving roots exposed to drying wind and sun.
- Bright winter sun heats up dark tree bark, which can freeze and crack when temperatures drop quickly at sunset.
- Deer, mice, rabbits and other animals gnaw bark and browse leaves and twigs when other food becomes scarce during long, cold winters.
Although wet, heavy snow can damage branches, snow cover is usually good for plants. A layer of snow provides moisture and helps insulate the soil and roots from fluctuating temperatures.
Preparing for the Big Chill
Healthy plants are more likely to get through winter unscathed. A plant that has struggled during the growing season, whether due to insufficient sunlight, water or nutrients, or heavy damage from insects or disease, will enter winter in a vulnerable state. Start your winter-protection strategy with careful care during the growing season and into autumn.
- Don't prune after midsummer. Pruning stimulates tender, new growth and delays dormancy.
- Stop fertilizing plants six weeks before the first fall frost, to help plants harden off properly.
- Water plants thoroughly throughout fall until the ground freezes; make sure the water penetrates 12" to 18" deep to reach the root zone.
Here are tips for specific types of plants:
Deciduous Trees and Shrubs
Deciduous shrubs and trees — those that lose their leaves in autumn — have adapted to life in cold-winter climates by going dormant. Many of these techniques are designed to ensure that plants enter dormancy before the coldest weather arrives, and remain dormant until spring.
Mature trees and shrubs that are hardy in your region need no extra protection. However, young and newly planted trees and shrubs benefit from some extra TLC:
- Because plant roots may not have ventured very far into the native soil, it's especially important to water newly planted trees and shrubs thoroughly into fall, until the ground freezes.
- Once the ground is frozen, apply a 3" to 4" layer of insulating mulch, such as bark mulch or pine straw, around the base of the plant. This helps insulate the soil so it stays frozen and helps prevent heaving. Keep the mulch several inches away from the trunk to prevent rot and discourage rodent chewing.
- Tender young bark is easily damaged by gnawing mice and rabbits. Protect the trunks of young trees — especially fruit trees — with tree guards made of plastic or wire.
- The bark of young trees is also susceptible to sunscald. Paint the south side of the trunk with a solution of diluted white interior latex paint or wrap the trunk with paper tree wrap. This also helps prevent frost cracks, which occur when dark-colored bark heats up on a sunny winter day and then rapidly cools at night.
You can find tree wrap and guards at garden centers and hardware stores.
Conifers and Broadleaf Evergreens
Trees and shrubs that remain green — conifers and broadleaf evergreens, such as rhododendrons — slow their growth but never go fully dormant. It's especially important that they have a ready supply of water whenever the ground isn't frozen.
- Drying winter winds are especially damaging to evergreens. In exposed, windy areas, erecting a windbreak helps prevent damage, as can wrapping shrubs with burlap or easy-to-use shrub wraps.
- If branches are bending under the weight of a heavy snowfall, gently remove some of the snow. However, don't try to remove ice after an ice storm; you're likely to cause more harm than good.
- Some evergreens, notably white pines, are susceptible to damage by road salt sprayed onto branches by passing snowplows. In spring, you'll see brown needles on the road-facing side of the tree. Protect hedges and shrubs with burlap or shrub wraps. On taller trees, there is little you can do; consider replanting with more salt-tolerant species.
- Keep deer from browsing on hedges and shrubs by wrapping them with burlap or shrub wraps.
Our innovative Rosy Cozy™ protects roses from extreme cold and temperature fluctuations.
Key features of the Rosy Cozy
Many shrub roses and rugusa roses are hardy and need no winter protection, but hybrid teas are another story. These tender, grafted roses need extra protection in regions where temperatures may drop below 10 degrees F.
- When the ground has begun to freeze and plants have dropped most of their leaves, prune canes back to 10" to 12" high, leaving at least three healthy buds on each. Choose the strongest, most vigorous canes and remove the weakest, thinnest canes right to the ground. Strong canes should be at least the diameter of a pencil.
- Pick any remaining leaves off the canes, and rake up and remove fallen leaves, because they can harbor disease organisms.
- We recommend covering your rose with our innovative Rosy Cozy™ Rose Cone to protect it from extreme cold and temperature fluctuations. Place the wire cage over the pruned-back plant and add insulating material, such as bark mulch, taking care to cover the graft union, which is especially vulnerable to cold temperatures. (The graft union is the swollen area near the base of the plant where the rootstock was joined to the top part of the plant.) Slip on the white tarpaulin cover and place bricks in the stirrups to anchor it. In contrast to styrofoam rose cones that suffocate plants or crumble and blow away, the Rosy Cozy is durable and reusable, with a mesh top that allows excess heat escape.
- If you are not using a Rosy Cozy, then pile bark mulch over the graft union. Be sure to check the plant throughout the winter to be sure the mulching material hasn't blown away.