Outdoor plants require specific protective measures to survive the dormant season. The primary threats are desiccation, or “winter burn,” which occurs when evergreen foliage loses moisture faster than roots can absorb it from frozen soil. Another danger is frost heave, where repeated freezing and thawing of soil pushes shallow-rooted plants out of the ground. Freezing temperatures can also damage cell structures, leading to tissue death. Preparing plants for winter involves pre-season transition, physical insulation, and ongoing monitoring.
Preparing Plants for Dormancy
The transition to winter survival begins long before the first frost, requiring plants to be “hardened off” to slow metabolic activity. Gardeners should gradually reduce watering frequency starting in late summer or early fall. This signals to the plant that conditions are less favorable for growth, encouraging it to prepare for cold weather rather than producing tender new tissue.
Cease all nitrogen-heavy fertilization by mid-to-late summer. Nitrogen promotes lush, leafy growth highly susceptible to cold damage. Continuing to feed plants late in the season results in soft growth that lacks the cellular density needed to withstand freezing temperatures.
Only light pruning should be undertaken, focusing solely on removing dead, diseased, or broken branches. Heavy structural pruning should be deferred until late winter or early spring. New cuts can stimulate late-season growth flushes that will be killed by cold, draining stored energy the plant needs for survival.
Marginally hardy container plants benefit from strategic placement. Move these pots close to a south- or west-facing wall for residual heat and a buffer against cold winds. Grouping containers together reduces the surface area exposed to freezing air, offering a collective insulating effect for the root balls.
Protecting Roots and Soil
Protecting the root zone is important because roots lack dormancy mechanisms, making deep freezing particularly damaging. Soil insulation is achieved through applying a deep, loose layer of organic mulch. This layer stabilizes soil temperature and prevents the alternating freeze-thaw cycles that cause frost heave.
Shredded leaves, straw, or wood chips are excellent materials because they trap air, acting as a thermal buffer. Apply four to six inches of mulch over the root zone after the ground has frozen hard. Ensure the mulch does not directly touch the plant’s crown or stem to prevent rot.
For established trees and shrubs, creating a temporary collar around the base before mulching keeps the material in place. This technique concentrates insulation directly above the shallow feeder roots. The mulch layer must be thick enough to impede heat transfer but loose enough to avoid compaction.
Container plants require specific attention since their roots are exposed to air temperature fluctuations. One effective method is to bury the pots directly into the ground in a sheltered area, using the surrounding earth as insulation. Alternatively, wrap the pot in insulating materials like bubble wrap or burlap, and place the vessel on a piece of foam board to prevent cold transfer.
Above-Ground Protection Techniques
Above-ground techniques mitigate environmental damage from wind and sun. Evergreen shrubs are susceptible to desiccation, or “winter burn,” caused by moisture loss through their leaves. Wrapping these plants in burlap or porous horticultural fabric creates a barrier that slows evaporation while allowing air circulation.
This physical barrier is beneficial on windy days, which accelerate water loss. The wrapping should not be excessively tight to allow foliage to breathe and prevent moisture buildup that encourages fungal diseases. For exposed sites, temporary windbreaks using stakes and burlap can reduce the drying effect of winter gusts.
Young or newly planted specimens benefit from constructed shelters. A-frame structures or cages filled loosely with straw provide a pocket of insulating air around the plant. These shelters shield the plant from heavy snow loads and ice, preventing physical breakage.
A specific concern for trees is sun scald, which occurs when bark on the south or west side warms significantly during the day and rapidly freezes at night. This rapid temperature fluctuation causes the bark to split and crack. Protect trunks using commercial tree wrap, applied from the ground up to the lowest scaffold branch.
An alternative for sun scald prevention is painting the trunk with diluted, light-colored latex paint. The light color reflects sunlight, minimizing the temperature differential between day and night. This prevents the cellular damage that leads to cracking.
Winter Maintenance and Monitoring
Ongoing care ensures environmental conditions do not overwhelm preparatory measures. Even when dormant, plants require moisture, and prolonged dry, freezing weather is damaging, especially to evergreens. Occasional watering should be performed during mild spells when the air temperature is above 40 degrees Fahrenheit and the ground is not frozen solid.
When heavy snow falls, the weight can cause structural damage to branches. Gently brush the snow off the branches with a broom, moving upward, but avoid shaking brittle, frozen wood. This replenishes moisture lost through transpiration and prevents desiccation damage.
During sustained warmer weather, inspect plants for signs of pests or fungal activity under protective coverings. Early detection of issues allows for adjustments to ventilation or protective placement. Avoid using road salt or de-icing agents near plant root zones, as salt runoff increases soil salinity and causes chemical desiccation.