The Hampton Gardener: Winter protection

Come early spring, all of the horticultural newsletters, magazines and gardening columns review what inevitably comes out as “the ravages of last winter” and my forecaster is still insisting that this winter will be one like we haven’t had in nearly a decade.

It seems that if one winter problem won’t kill your rhody, boxwood, hydrangea, yew, prized rose or 30-year-old pine then another one will. Most of the damage, though, is not an act of nature as much as the lack of action by man. Put simply, most winter losses are avoidable.

On one hand, we are most fortunate in that our winters tend to be mild with gradual fluctuations in temperatures rather than wild swings above and below freezing that can destroy woody plant material (trees) and heave shallow rooted ground plantings. Unfortunately, our maritime climate also results in erratic snowfalls that tend to be light and quickly melted though we are also subject to storm systems that straddle the East End between cold and warm boundaries, which can translate to heavy wet snow that is hell on many evergreens.

Now, I hate snow, but there are times in January and February when I can be seen running around the yard, arms stretched skyward while in a pleading voice I beg, “Snow, please snow.” As it turns out, the white stuff is the best insulator that Ma Nature can provide. It protects the ground and the plants in it from freezing and thawing thus maintaining a relatively uniform temperature while the plants remain calmly dormant. The snow even stimulates many wildflower and perennial seeds toward germination and protects several species of lawn grasses from disease. But since we rarely get enough of the stuff, we have to provide the best substitutes in the form of winter mulches.

Unwisely, many gardeners apply this mulch too early in the fall. This early application does not allow the ground to freeze and encourages soft green growth that is soon destroyed when the first super cold spell sets in. Early mulch application also results in the phenomenal buildup of rodents such as mice and voles. These rodents then feed on the roots and low level bark (voles) and shoots (mice) since the ground won’t freeze and soft green shoots become culinary delicacies. To further compound the problem, the mulch becomes a nesting area for voles whose reproductive urges have been stimulated by the protection.

Unlike mice, the voles will continue to produce young right through the winter, but only if they have nesting and food, which you may be inadvertently providing. The solution is simple. Don’t apply winter mulches until the ground is frozen hard and the freeze that we usually have around Thanksgiving, even though it can leave ice on ponds and lawns crunchy, does not constitute a hard freeze from a horticultural point of view, only a meteorological one.

If applied to solidly frozen ground, the mulch will keep it frozen in spite of much higher air temperatures on mild days and it also keeps the warming sun’s rays off the ground around the plant further stalling any thaw. Since the ground is frozen, the rodent problem is somewhat reduced, though voles and mice may still gnaw on the bark of some ornamentals such as trees and shrubs.

Voles seem to be particularly fond of apple and quince, as I learned several years ago when gardeners mulched the quince bed too early and too close to the plant crowns and in the spring when we pulled back the mulch each and every plant was gnawed at ground level. These types of plants can be protected with something as simple as an aluminum foil wrapper or a commercial plastic product such as Tree Guard. But having learned, we now only mulch up to 6 inches from the trunks and stems and never around the crown.

A number of materials are used for mulching, such as hay, straw, pine needles and bark chips, but the best is salt hay. Three to 5 inches of well fluffed salt hay protects as well as 6 to 8 inches of snow, it contains few if any weed seeds and it can be recycled in the summer as a summer mulch to retain soil moisture and reduce weeds in unplanted areas or between plantings. A bale of salt hay goes a long way, but it is always in short supply when you need it. If you buy it now or already have some on hand, protect it from any rain or come the day you decide to put it down you’ll need an ice pick and blow torch to break it up.

The other winter problem that we have is wind. Next to hating the snow, the wind gets my second vote. It comes out of the north to northwest and unlike our humid summer winds the winter wind is fast, dry and destructive. The problem is called desiccation and it occurs as the dry wind passes over the foliage of broad and narrow leaved evergreens causing the moisture in the foliage to evaporate very quickly. Rhododendrons and their relatives react by curling their leaves to reduce the surfaced area exposed to the wind. Needled trees such as pines are not as fortunate and they react with needle drop, loss of color and in the severest of winters, possible death. Boxwoods on the other hand may not show the damage until the spring when we expect them to green up even more but instead they brown as an expression of the damage done to both roots and shoots.

The problem is particularly bad when the ground is dry or frozen hard and the tree or shrub can’t draw moisture from the ground to replace that which has evaporated. Other than constructing windbreaks (which are popular on ocean and bayfront properties) there are two choices.

Each winter for the past dozen or so years we’ve made a burlap shelter around the boxwoods on the north side of the house. This protects them from the wind and from snow cascading off the roof. It’s a day-long chore and I suspect that many times we’ve done more damage driving stakes into the low voltage power lines that go to the landscape lighting and the irrigation lines than we’ve done to benefit the boxwoods. But last winter the boss complained bitterly about these sarcophagus encapsulations (“Andrew, they’re just plain ugly!”), so we went to plan B. Using heavy garden twine, the groups of bushes were encircled with the twine that was then pulled tight causing the shrubs to essentially huddle and insulate themselves. And since the mass was reduced and supported by the surrounding twine the snow loading wasn’t an issue. It worked. Nonetheless I’m still skeptical, so stay tuned.

There is another solution and it comes in spray cans (for small properties) or in quarts and gallons. The products are called anti-desiccants and they essentially coat the foliage with a long lasting film of a latex, wax or plastic-like material that allows the plant to breathe (transpire), but gives protection from over evaporation in the wind. The products are sold under the trade name such as Wilt-Pruff and Vapor Guard and it may be wise to apply the material several times from January through early March. In some cases the products are mixed with the fungicide Thiram and the combination offers a long-term (8-10 weeks) deer repellency as well.

The down side (there always is one isn’t there?) is that some of these products can leave a white cast on the foliage and if the winter is a dry one it can be mid to late spring until the white fades. There is also some question regarding the effectiveness of these products, but between the three choices noted above I’d pick one as opposed to none for valued plants in this category.

Remember also that burlap baffles also work to protect evergreens from salt spray from the ocean and bay as well as a degree of protection from road salters.

Keep growing.

Andrew Messinger has been a professional horticulturist for more than 30 years. He divides his time between homes and gardens in Southampton, Westchester and the Catskills. E-mail him at: Andrew@hamptongardener.com. The Hampton Gardener is a registered trademark.