Evergreens, with their year-round foliage, offer structure and color to the landscape, making them desirable additions even during the coldest months. While it may seem counterintuitive, planting these trees in winter is often possible, particularly in climates with mild temperatures and periods of thaw. Successfully transplanting an evergreen in this season depends entirely on meeting specific environmental requirements and employing specialized techniques. The key is ensuring the tree can establish initial root contact with the soil before a deep, prolonged freeze locks the ground solid.
Defining the Planting Window
The most successful winter planting of evergreens occurs during late fall or early winter, before the soil undergoes a hard, sustained freeze. This timing allows the tree to take advantage of its semi-dormant state, minimizing the shock of transplanting. Unlike deciduous trees that enter complete dormancy, evergreens retain their foliage, meaning they still lose some water through transpiration. This reduced activity is beneficial because the tree is not actively supporting new top growth while establishing a root system. Mid-winter planting is only advisable in warmer regions or during temporary thaws in colder zones, provided the ground is fully workable.
Essential Soil and Climate Requirements
The physical state of the soil is the single most important factor determining if a winter planting can proceed safely. The ground must be completely unfrozen and easily workable. Attempting to dig into frozen soil is impossible and can severely damage the root ball, while planting into a hole with frozen walls prevents new roots from expanding outward.
For active root growth to occur, the soil temperature needs to be above a minimum threshold, ideally remaining above 40°F (4°C). In regions with consistently harsh winters, the ground may freeze solid for months, making mid-winter planting impossible. Conversely, in southern climates that rarely experience a deep freeze, the planting window extends well into and through the winter.
The soil must also have adequate moisture content before the onset of freezing conditions. If the soil is dry when it freezes, evergreens are highly susceptible to winter desiccation. A well-drained, moist soil is necessary to act as a thermal buffer, holding more residual heat and insulating the root zone from rapid temperature fluctuations.
Step-by-Step Cold Weather Planting
Successful cold weather planting requires careful preparation to mitigate the risks associated with low temperatures. It is beneficial to prepare the planting hole ahead of time if a hard freeze is anticipated, keeping the excavated soil covered in a garage or shed to prevent it from freezing. The planting hole should be dug two to three times wider than the root ball but no deeper, ensuring the top of the root ball sits slightly above the surrounding grade.
When placing the evergreen, the root ball must be handled gently and kept moist, shielded from drying winter winds and cold shock. Backfilling the hole should be done with unfrozen, native soil, potentially mixed with a small amount of compost, but without heavy organic amendments that could lead to poor drainage. Avoid fertilizer applications, as stimulating new top growth is counterproductive during this time of year.
The soil around the root ball must be tamped lightly to remove any large air pockets, which can expose the roots to damaging cold. A final, thorough watering is necessary immediately after planting to settle the soil and eliminate any remaining air gaps before the ground freezes solid. The use of unfrozen soil is paramount, as frozen clumps restrict root-to-soil contact.
Protecting Evergreens After Winter Planting
Immediate and sustained care following a cold-weather planting is vital for the evergreen’s survival through its first winter. A thick layer of organic mulch, approximately three to four inches deep, should be applied over the entire root zone, extending out beyond the dripline. This heavy mulching insulates the soil, helping to moderate temperature swings and prevent frost heaving, but it must be kept several inches away from the tree’s trunk to prevent rot.
Evergreens are highly susceptible to winter burn, a form of desiccation caused by moisture loss from the needles when frozen ground prevents water uptake. Applying an antitranspirant spray can help by forming a thin, waxy coating on the foliage to reduce the rate of water vapor transmission. This protective film lasts for several months, helping the tree retain internal moisture.
Physical barriers, such as burlap screens or temporary fencing, should be erected on the south and prevailing wind sides of the new planting. These screens shield the foliage from the harsh, drying effects of direct winter sun and strong winds, which contribute to desiccation damage. Winter watering is a necessary practice during dry periods when the air temperature is above freezing and the ground is not frozen, replenishing lost moisture.