The arrival of cold weather introduces several threats to plants, including desiccation, root damage, and the risk of branch breakage from ice or heavy snow. Successful winter protection combines long-term preventative care with immediate, active intervention before severe cold events. Preparing plants weeks in advance and using temporary shelters significantly increases the likelihood of survival during the dormant season. Protection focuses on stabilizing the plant’s environment and minimizing the loss of internal moisture when the ground is frozen.
Essential Pre-Season Preparation
A foundational step in plant winterizing involves deep watering the soil just before the first sustained freeze to prevent “winter drought.” Evergreens, in particular, lose moisture through transpiration even when temperatures are low. If the soil is frozen, their roots cannot absorb replacement water. Providing up to an inch of water per week until the ground freezes ensures the root zone is saturated, offering a reservoir of moisture that mitigates desiccation.
Applying a thick layer of organic mulch around the base of plants stabilizes soil temperatures and protects the root system. A two to four-inch layer of shredded leaves, straw, or wood chips reduces the number of freeze-thaw cycles. This prevents frost heaving, which pushes shallow-rooted plants out of the ground. The mulch should not touch the plant’s trunk or stems, as this can trap moisture and encourage disease or rodent damage.
Gardeners should stop applying nitrogen-heavy fertilizers by mid-to-late summer to allow plants to “harden off.” Nitrogen encourages the growth of tender, new shoots highly susceptible to frost damage. Stopping fertilization signals the plant to focus energy on carbohydrate storage and strengthening cell walls, which increases cold hardiness.
Pruning should be avoided late in the season because fresh cuts can stimulate new, vulnerable growth damaged by the first frost. While minor deadheading may be acceptable, major structural pruning should be postponed until the plant is fully dormant or until late winter. This ensures the plant enters the cold period with maximum stored energy and minimal exposed tissue.
Implementing Active Cold Protection
When severe temperatures or strong winds are expected, physical barriers offer immediate protection for above-ground plant parts. Covering vulnerable shrubs and small trees with breathable materials like burlap or specialized fabric deflects drying winds and filters harsh sunlight, preventing winter burn. These covers should be tented over the plant and secured to stakes. This prevents the material from lying directly on the foliage, which can transfer cold and cause damage.
For smaller plants or vegetable beds, simple temporary structures such as cloches or cold frames provide a sheltered microclimate. A cloche, often a clear plastic dome or glass jar, traps residual heat from the ground, protecting individual plants. Cold frames are low, box-like structures with a transparent lid. The lid can be propped open for ventilation on sunny days, allowing for short-term growing or hardening off.
Protecting the trunks of young or thin-barked trees prevents sunscald. Sunscald occurs when dark bark rapidly warms on a sunny winter day and then freezes quickly at night, rupturing the cells. Wrapping the trunk from the base up to the first branches with commercial tree wrap or a light-colored material reflects the sun’s rays and stabilizes the bark’s temperature. Upright evergreens, such as arborvitae, can also be loosely tied with twine to prevent heavy snow or ice from splaying the branches outward and causing structural breakage.
Snow acts as a beneficial insulator, especially for low-growing perennials, because the air trapped within the snowpack maintains a stable temperature just above freezing. Heavy, wet snow or ice accumulation on tree and shrub branches should be removed carefully. Instead of shaking brittle, frozen branches, use a broom to gently brush the snow upward from the underside to minimize the risk of snapping the limbs.
Special Care for Container and Tender Plants
Container plants are highly susceptible to cold damage because their root systems are above ground and exposed to freezing air temperatures. A practical strategy is to group pots tightly together against a sheltered wall of a building, such as a south or west-facing side, to utilize residual heat and block wind. This clustering helps insulate the pots from each other, increasing the overall root-zone temperature.
To further insulate the roots, containers can be wrapped in materials like bubble wrap, burlap, or straw, which adds an air layer of thermal protection. Lifting the containers off cold concrete or stone surfaces using small blocks or “pot feet” prevents direct heat transfer from the root ball to the ground.
Tender perennials or tropical plants that cannot tolerate freezing temperatures must be relocated to a protected space, such as an unheated garage, shed, or basement. If the plants are dormant, their need for light is minimal, but the temperature must remain cool yet consistently above freezing to prevent growth while avoiding root death. Non-hardy bulbs and tubers, such as dahlias and cannas, should be dug up, or “lifted,” after the first light frost. The harvested tubers are then stored in a cool, dry, dark place, often in peat moss or sawdust, until spring planting.