By Kimberly Toscano
Winter weather is unpredictable. In Southern states especially, unexpected cold snaps and constantly shifting temperatures can take their toll on plants in the landscape. A few easy tasks can help you protect plants and minimize winter damage.
1. Add a Layer of Mulch
Mulch is a garden miracle-worker any time of year and an important part of winter care. Think of mulch like a blanket protecting the garden during the winter months. A common winter problem is heaving or uplift of soils caused by freeze-thaw cycles. Soil heaving can literally push shallow-rooted plants like heucherella and gaillardia out of the ground, exposing the tender crowns and roots to freezing temperatures. Mulch helps keep soils consistently cold, preventing the disruptive freeze-thaw cycles. Mulch also helps maintain soil moisture and provides insulation for marginally hardy plants.
Apply a thick 3- to 5-inch layer of mulch after the first hard freeze. It is not necessary to purchase wood mulch for winter applications. Light-weight materials such as chopped leaves and pine straw are ideal because they won’t compact.
2. Winter Watering
It may seem pointless to water gardens in winter when many plants are dormant, but there are good reasons to provide irrigation during the winter months. Evergreen trees and shrubs loose a great amount of water during cold, dry weather, particularly on windy days. Unless rainfall is sufficient, these plants need supplemental irrigation at least once per month during the winter months to keep soils moist. Even dormant plants benefit from winter watering. Many plants continue to actively grow roots even when the canopy is dormant.
Soil moisture also protects both dormant and evergreen plants during cold snaps. Moist soils hold more heat than dry soils, so the potential damage to plants’ roots during the cold weather increases if the soil is dry. Watch the weather forecast and be sure to irrigate all plantings at least 24 hours before hard-freezing weather arrives. Also keep an eye on plants under eaves and in containers, which tend to dry out faster than other areas of the landscape.
3. Protect Sensitive Trees
Trees with thin or smooth bark may benefit from a trunk wrap in late fall to protect the trunk against a condition called southwest injury or sunscald. This type of damage is caused by alternate freezing and thawing of water in the trunk and occurs on the southwest portion of the trunk which is exposed to warm afternoon sun. Wrap young, thin-barked trees with a commercial protective material to prevent winter sunscald. It is important to remove trunk wraps in spring to avoid damage.
Newly planted trees may also require stabilization, but not all trees require staking. To determine if staking is necessary, shake the tree gently from side to side. The base of the tree should remain steady within the ground. If you can see the rootball move, stake the tree for winter.
When it comes to staking, less is more. Stake the tree only during the winter months and be sure to remove staking materials in spring. Strings and ties left around the trunk as the tree develops can eventually become tight and potentially kill the tree.
4. Container Plants in Winter
Some plants can winter over in containers with no problem while others require protection. When we select plants for the garden, we use USDA winter hardiness ratings to choose plants that can tolerate our winter temperatures. Those cold-hardiness ratings assume plants spend the winter tucked safely in the ground, where temperatures remain between 35 to 45 degrees F. Without the extra insulation garden soil provides, many container plants can’t survive outdoor winters.
A good rule of thumb is to consider the climate of a container to be two hardiness zones colder than your local climate. If you live in zone 7, for example, then the container plant must be hardy to zone 5 to survive winter in a container. Consider bringing container plants indoors or wintering them in a sheltered location if they cannot tolerate the cold. Often, simply covering plants on the coldest of nights is enough to get them through the winter.
5. Remember to Protect Water Features
Most small water features require some winter preparation to protect your investment over the winter. The number one rule is do not allow the pump to freeze. In areas where freezing may occur, remove the pump and store indoors over winter. Ceramic water features such as vases can crack with freezing temperatures. In cold areas, it is best to drain water from ceramic features and move them indoors over the winter.
For water gardens, remember to bring any tropical plant materials such as colocasias and tropical water lilies indoors over the winter. Check with your local garden pond experts about how to determine if your pump will move water all winter or if it should be removed and stored until winter.
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