The shift from active growth to winter survival requires a series of deliberate actions to ensure outdoor plants endure freezing temperatures and harsh conditions. The goal of winterizing is to prepare the plant’s physiology for a necessary period of dormancy and to insulate its most vulnerable parts, not to encourage new development. Different types of plants, from established landscape shrubs to container specimens, require distinct methods of intervention. Planning ahead and executing these steps weeks before the first hard frost increases the chance of a vibrant, healthy return in the spring.
Preparing Plants for Dormancy
Successful winter survival begins with a physiological shutdown initiated during the late summer and early fall. Stop all nitrogen-heavy fertilization by late summer, as continued feeding promotes tender new growth highly susceptible to frost damage, signaling the plant to redirect energy toward hardening off existing tissues. Water management also needs adjustment; reduce late-season watering to encourage the plant to “harden off.” Ensure the soil is thoroughly watered just before the ground freezes, especially for evergreens, since well-hydrated plant cells are less prone to freeze injury. Pruning should be limited to removing only dead, diseased, or damaged wood, as heavy trimming can stimulate new growth that will be killed by the cold.
Protecting In-Ground Plants from Frost and Wind
Plants rooted in the landscape require insulation around their root zone and protection from desiccation caused by winter wind and sun. After the ground has frozen, apply a deep layer of organic mulch, such as straw or shredded bark, two to four inches deep around the base. This layer stabilizes the soil temperature, preventing the damaging cycle of repeated freezing and thawing that can heave shallow-rooted plants out of the ground. Keep the mulch several inches away from the plant’s crown or trunk to prevent moisture buildup or cover for rodents. For broadleaf evergreens, construct a simple screen using wooden stakes and breathable burlap to filter the drying winter wind and intense sun, which cause the leaves to lose more water than the frozen roots can replace.
Strategies for Container and Potted Plants
Container plants face a unique challenge because their roots lack the insulating mass of the surrounding earth, making them more vulnerable to air temperatures. The roots may experience temperatures two USDA hardiness zones colder than an in-ground plant of the same species. The most effective method for smaller containers is to move them to an unheated but sheltered space, such as a garage or cold frame, where temperatures remain consistently between 20°F and 45°F. If a plant is too large to move, the container must be insulated to buffer the root ball from freezing air. This can be achieved by grouping pots tightly against a protected wall and surrounding them with straw bales, or by wrapping the pot in multiple layers of bubble wrap, foam insulation, or burlap.
Winter Damage Assessment and Recovery
After the worst of the cold has passed, patience is necessary before taking recovery action, as the full extent of cold damage may not be immediately apparent. Wait until the danger of hard frost is over and new growth begins before removing protective covers. Resist the urge to immediately prune away seemingly dead branches, as the plant may still push out new growth from tissue that appears brown or damaged. To check for viability, perform a simple scratch test on woody stems: green tissue underneath the scraped bark signifies the branch is alive, while brown tissue indicates death. If a deep freeze has occurred, avoid heavy watering until the soil has completely thawed to prevent root rot.