While thinking about topics to share this week, the obvious hit me in the face – literally. Wind tore my hat off; branches smacked me as I hiked with the dog; a fallen old Scots pine blocked the path to the pond. Wind made many of our lives miserable this week and caused some landscape damage.
It was a warning: Wind will cause more problems this winter. Wind is a major cause of plant stress and death, whether quickly or gradually. Now is a fine time to protect the most vulnerable plants in your landscape, to prepare trees so they will incur the least damage, and to anticipate what havoc the wind may incur. If you can’t prevent all the damage, you can understand it and make different choices next time.
At risk of embarrassing someone, let me ask you, just between us: From what direction does the wind blow at your house? Which way is east, south, west and north anyway? You’d be surprised how many people are directionally challenged, but this is important to know: The wind usually comes from the west (or southwest or northwest), with some turnabouts during storms. Your garage or nearby buildings or fences can also influence the wind’s direction, so observe carefully.
Now consider the ways that wind does its dirty work, and calculate the choices you have.
If you drive around treed neighborhoods or walk in a forest after a serious windstorm, what trees do you notice that are toppled with their roots exposed to the air? Colorado blue spruces (often with green-colored needles), and some other tall evergreens, are likely candidates. Look at the whole root system, lying before you. Even for trees that were 40 feet tall, the root systems are very shallow and not very wide. If you were an engineer you wouldn’t design a vertical object with such a flimsy anchor – but most of the time the fault is not in nature’s design. Landscape and urban trees rarely get the soil, site conditions and care that they need. Ideally, to give trees the best odds of flourishing, we all would select species meticulously, care for them properly for all their years and site them where gale winds don’t threaten.
While some kinds of trees (willows, sugar maples, pin oaks) have extremely shallow root systems, it’s important to understand that almost all trees (especially in our region) grow most of their roots in the top few inches of soil and do not have tap roots. The image of a tree with a deep tap root was imprinted in our brains in elementary school if we are over 40 years old, for sure. (This may be true of younger people, too, as I am not sure how soon all the science teachers and texts caught up with modern arboriculture science).
However, every plant science department today will tell you firmly that most tree roots are in the top few inches of soil, and naturally grow outward about three times as wide as the canopy. Those few trees that are capable of growing a tap root, such as some pines and oaks, only do that in sandy, well-drained soil. In Western New York and other places with clay or otherwise impenetrable soil, that does not happen.
So – if they don’t have deep tap roots, why do some trees (London plane trees, sycamores, beeches, sour gum) rarely blow over? Two answers: If they have good wide-spreading root systems, and nothing is allowed to damage the roots (nearby construction, traffic, trenches, heavy weights compacting them) they are anchored. Or, they have airy canopies that let the wind blow through (versus solid canopies that act like sails). Or perhaps a professional arborist lightened the canopy and provided that airiness. Valuable old trees should meet a tree professional sometime; they’re likely to live longer.
Windburn and desiccation
Windburn resembles a burn, typically on the windward side of an evergreen, whether it has needles or fleshy leaves such as a rhododendron. Wind speeds up “transpiration” (moisture loss) and kills the leaves when the roots cannot replace it because the soil is frozen. This happens less quickly if the plant was well watered before the ground froze. The damage will also be less if you provide water to the roots any time the temperature warms and the soil dries out. Dry, windy winters are the most dangerous for plants: Snow is excellent mulch. Other mulches, put over the root systems when the soil is wet, also help retain moisture.
In the case of the most vulnerable plants (rhododendrons, Japanese pieris, some hollies, azaleas and boxwoods), how can you avoid wind damage? With hindsight, those plants would have been better sited on the east side of a building or sheltered by a windbreak or fence. You might put up a snow fence to buffer the wind. I use and believe in the Shrub Coat line of products that includes individual sacks or tee-pees of all sizes to cover single plants, and flat shrub screens that act as fences. Made in the United States, designed by a local landscaper, they are green, deer-proof, have 10-year warranties, and they let your rhododendron emerge in spring intact and green. Burlap is an old stand-by, but deer and wind can pull it to shreds, and it’s ugly. Do not wrap or cover any plants with plastic.
Anti-transpirant products such as Wilt-Pruf and CloudCover work to slow moisture loss by coating plant leaves or needles. You need not rush – some professionals wait until January when the ground tends to remain frozen. Spray on a day when the temperature is above freezing. It does no environmental harm, although it may temporarily discolor blue-toned plants. It can last up to four months in the winter.
Ultimately, wind is stressful to live with, for us and our landscape plants. But thoughtful plant selection, siting and protective products improve the health and survival rate of trees and shrubs even in spots that feel like wind tunnels.
Sally Cunningham is a garden writer, lecturer and consultant.