Believe it or not, spring is on the way. Each day is a bit longer than the last, and we’re almost through January, typically one of the toughest winter months to endure.
So far, this winter has been a bit of a weather roller coaster. In much of the country, we were rocked by an unusual event, the polar vortex, an icy arctic blast that produced record-low temperatures. This was followed by a thaw that raised the mercury to the 40s, showing just how unpredictable nature can be.
This seesawing of temperatures is very hard on plants, especially evergreens. Extreme cold temperatures make anything holding moisture brittle, and added weight from snow and ice strains stems, branches and trunks, often causing them to break or crack.
For many evergreen plants the biggest problem during cold weather is access to moisture at their roots. When soil freezes, any water that is above the frost line becomes rock hard and is no longer available to the plant’s roots.
When water is no longer available to the plant, and while it is still transpiring moisture through its leaves, the plant suffers what is called winter burn. Essentially, the outer edges of the leaf or stem die and turn brown. Severe winter burn can cause the entire leaf to turn brown and fall off.
Mild cases cause only cosmetic damage, but extreme cases can kill a plant.
Broad-leaved evergreens such as azaleas, rhododendrons, holly, mountain laurel, boxwood and Southern Magnolias are particularly susceptible to winter burn, as are evergreen groundcovers like ophiopogon and liriope.
One way to help prevent winter burn on evergreens is to plant them where they will be protected from harsh winter winds. Winter wind rapidly removes moisture from leaves. For added protection, wrap the plants in burlap. You needn’t worry about blocking sunlight from the plant since it will be dormant during the winter months.
In fact, keeping the sun off the leaves is another good way to protect Broad-leaved evergreens during the winter months. If at all possible, site your plants in areas that receive winter shade. It will greatly reduce their chances of winter burn.
Contrary to what you might think, the winter sun, rather than having a warming effect on your plants, dries them out instead. This is especially true if their roots are frozen solid with no access to water.
My zone 6 garden is about the northern edge of hardiness for a tree like a southern magnolia. Many years ago, I planted one in a location shaded all winter long by some large western cedars; not only has it thrived, but its beautiful dark green glossy leaves show no signs of winter damage.
Another way to help small broad leaved plants survive the winter with minimal damage is to cover them with evergreen boughs. This is very helpful especially in areas with cold temperatures and minimal snowfall.
Snow cover helps many plants since it buffers them from desiccating winds and keeps temperatures steady. We get sporadic snowfall where I live, so I compensate by placing pine boughs over my dwarf evergreens as well as over my beds of black mondo grass (aka ophiopogon), another plant growing at the far edge of it’s cold tolerance.
The branches create shade and keep wind damage to a minimum. If you don’t have access to pine boughs where you live, salvaged branches from discarded Christmas trees will work nicely too.