Nov. 20 2019 06:00 AM

Winter can take a toll on plants and trees, but there are ways you can help lessen its impact.

As the winter season approaches, our thoughts are naturally consumed with the excitement of upcoming holidays, while many of us anxiously watch the weather forecast awaiting the first snow of the season. It’s also the period of time when trees and perennial plants go dormant, storing up energy for the spring, when they will once again burst forth with showy blooms and green leaves.

But just because the plants are sleeping, so to speak, they still need protection from the elements. Your clients may not fully appreciate just how precarious a plant’s life can be during the cold season. Even if its stems and branches avoid injury by snow, ice and wind, they may still feel the teeth of rodents biting into them. And even though precipitation in the form of snow may cover the ground, the moisture level in that soil can be depleted to critical levels, just as it can during the heat of summer.

In the absence of shading leaf canopies, sun scald becomes a real possibility for deciduous trees. And then there’s man-made injury caused by snow plows and the application of road salt.

Although your clients may not see you as much as they would during the growing season, if you’re a landscape professional who does more than simply “mow and blow,” you will want to put a plan in motion to see your clients’ trees, shrubs and ground covers through to the spring.

Winter plant protection isn’t something most landscape companies choose to promote in their menus of services. It will often be categorized under another heading, such as “fall cleanup.”

Picking the right plants

Winter care starts in the spring, before planting holes are dug and while pictures of plants in magazines and catalogs tantalize homeowners. How those plants will fare during December, January and February isn’t likely to cross your customers’ minds.

Just because a particular plant looks nice in a magazine or catalog doesn’t mean it’s hardy enough to stand up to the kind of winter you typically have in your region. Early in the planning and planting stages, you can guide your clients to more enlightened decisions, saving them much grief and expense come March.

“Plant selection is important,” says Jeff Gerety, owner of Gerety’s Professional Landscape Service Inc., Redding, California. Regions such as his, in northern California, host a full spectrum of microclimates and soil conditions — and not every plant will work in every one of them.

“It’s all about selecting the right plants, in the right variety, for the right situations. Successful wintering stems from a good spring plant layout for the climate.”

This is where Gerety’s experience — and yours — counts. He points out that winter is a good time to educate your customer base. Calling on your professional knowledge of plants and their requirements, he suggests using this less-busy time of year to educate them as to what will work best in their landscapes.

Your experience and expertise can also help guide customer decisions regarding the appropriate timing for cultural practices such as pruning and applying weed control and fertilizer, particularly if you are not the one delivering those services. For instance, fertilizing too late in summer or fall will stimulate new growth, which is more easily injured by the cold. Late-summer pruning can have the same effect.

Having such a discussion with your client is a good opportunity to suggest that your company take those chores over.

If a customer insists on a plant installation beyond the optimal planting season, stress the need for maintenance fail-safes that will help ensure survival. “If you’re installing plant materials close to when weather will be turning cold, especially evergreen plant material, make sure you mulch them properly and water them in well,” stresses Todd Vena, maintenance operations director for Mariani Landscape, Lake Bluff, Illinois.

A dry season

Just as humans can suffer from dry skin in the wintertime, the same sort of thing can happen to plants. Winter desiccation, or loss of moisture, is common, especially in conifers and broadleaved evergreens.

A good layer of compost or bark mulch covering the root zone of plants or trees will help ensure successful overwintering.
Photo: Native Edge Landscapes

As Brian Schroeder, owner of Elm Creek Landscape and Design LLC, Tulsa, Oklahoma, explains, “In winter, dry conditions can be more damaging than the cold itself. Cold winter air is usually quite dry, and winter winds can remove water from plants faster than the roots can absorb it. This is especially true of evergreens, as water evaporates quickly from their foliage.” When water is lost through evapotranspiration faster than it can be replaced because of dry or frozen soil, leaves and needles can become as scorched as they might from a 100-degree summer day.

If the winter (or fall) has been particularly dry, the irrigation schedule may need adjusting in order to ensure adequate soil moisture until spring. But in many cases, this could be achieved through proper mulching.

According to Steve Stewart, president of Landscape East and West, Clackamas, Oregon, “In the Portland area, the winters are usually pretty temperate, so unless you are working with plants outside of our climate zone, we recommend having a good layer of compost or bark mulch covering the root zone of the plants. That is usually enough to ensure a successful overwintering.”

The layer of mulch serves as an insulating blanket. Supplemental watering can also provide an insulating effect along with extra moisture. “Plant cells that are plump with water will be stronger against cold damage,” explains Schroeder. “Likewise, moist soil will tend to stay warmer than dry soil. A regular watering schedule in dry, cold weather can help protect plants from freezing temperatures.”

Despite your greatest efforts to encourage your clients to choose the right plants for the right site conditions, they’ll sometimes insist on choices that make desiccation inevitable.

“If plant materials are requested regardless,” says Vena, “we propose anti-desiccant applications or that actual winter protection — such as two-by-four framing clad with burlap or similar — be constructed.”

He emphasizes, too, that inconsistency with anti-
desiccants throughout the winter months is a common mistake in the effective use of these products. “When temperatures rise above freezing, additional anti-desiccant applications should be completed.”

Beating branch breakage

Snow and ice loads on the branches of trees and shrubs often leads to breakage. Maintenance decisions made well in advance of the first frost can lessen the impact. For instance, when pruning, it’s best to leave U-shaped branch crotches in place as they support heavy ice, snow and wind weight much better than V-shaped ones.

“Because we end up at times with ice storms,” explains Stewart, “we focus on good winter pruning to ensure we don’t have branches that will end up with too much excess weight. We will also wrap some upright conifers like Italian cypress, arborvitae or Taxus (yews) to keep their branches from spreading out too far from the main trunk.”

Damage from intense winter sunlight can impact the trunks of tender young trees missing the shade provided by their own leaves or the canopies of the other deciduous trees in the yard. David Ellis of Native Edge Landscapes, Boulder, Colorado, advises, “Make sure you are wrapping the trunks of trees with crepe paper to prevent sunscald, especially ones that are on the south or west sides of buildings.”

Critter control

When the herbaceous plants typically foraged by wildlife like rabbits and mice are hidden beneath the snow, they’ll turn to nibbling the tender cambium within plant stems. Periodic inspection of stems during the cold season is advisable to see if rodents are active.

If mulch was applied improperly during the fall, particularly in “volcano” fashion, piled against a tree’s trunk, it provides good winter shelter and a hiding place for mice and other rodents. Take the time to pull it back. Mulch should never touch tree trunks, as it can lead to rot and insect infestations.

However, damage by small mammals isn’t always confined to the lower portions of trunks. Scott McIntyre, president of West Hartford Landscaping Inc., West Hartford, Connecticut, says that in his region, heavy snowpacks allow rabbits to go higher, gnawing on limbs several feet above the ground.

“Depending on the plants and how particular the clients are, we’ll put forms or cages around shrubs and tree trunks and then wrap burlap, chicken wire or metal screening around them. That prevents the rabbits from damaging those trunks and plantings.”

Humane traps or poisons are sometimes considered, but these can be troublesome options. Animals that have been trapped will need to be transported somewhere and released. All mammals have the potential to carry rabies, and you don’t want to expose your workers to possible bites or scratches from diseased wild creatures. Poisons that kill rats and rabbits can also kill your client’s dogs and cats or those in the neighborhood.

Some treatments or products could require a commercial pesticide license in your state, and these may be different certifications than those that allow you to treat for insect damage.

Winter watering guidelines

If your soil stays frozen all winter, then fall is your prime time to make sure everything is well watered before the ground freezes.

If you experience freezing weather only occasionally, and you have had insufficient rain or snowfall, water deeply a day or so before a freeze is forecast, taking care to water a plant’s entire root system. A good rule of thumb is to water an area the same size as a plant’s dripline.

Be extra attentive to newly planted trees and shrubs. Not only are their roots less established, but the churned-up soil can allow cold air to penetrate deeper to the roots.

Water when the air temperature is above 40 degrees Fahrenheit. Don’t water if snow or ice is already on the ground.

Water early in the day so the plants have time to absorb it before the temperature drops at night.

List provided by Brian Schroeder, owner of Elm Creek Landscape and Design LLC, Tulsa, Oklahoma.


Stopping snow and snowplow damage

When a parking lot is blanketed in two feet of snow, the primary goal of the property owner becomes clearing the travel lanes and parking spots; the protection of the trees and shrubs in it can be outranked and overlooked. In such a scenario, damage from snowplows or shovels is a high probability. This can be mitigated by placing some sort of protective structure around tree trunks.

Wrapping the trunks of trees with crepe paper in the winter helps prevent sunscald, especially on ones that are on the south or west sides of buildings.
Photo: Native Edge Landscapes

McIntyre says a snow fence can be constructed out of a wood frame covered with chicken wire and burlap, similar to the rabbit protection structures his company utilizes. “A snow fence can protect valuable specimen plants from not only human error such as equipment damage, but also from snow sliding down on them from a roof,” he explains.

Protecting trees and plants from injury during snow and ice removal could be a good winter service offering for your company, particularly to commercial customers.

Correcting winter damage

Despite your best efforts, some plants may still emerge from the off-season with noticeable injuries.

Drooping, rolled or discolored leaves or needles that your client might interpret as cold damage could simply be signs of a plant’s natural defense mechanisms at work. In that case, the plant will recover on its own. You may need to convey this information to your clients and put their minds at ease.

However, scorched leaves, dead twigs and broken limbs are cause for corrective actions such as end-of-winter pruning.

Fertilizing and watering winter-damaged plants can help them compensate for their January and February losses once spring arrives. Plants that have been pushed out of the ground by frost heave will need to be replanted as soon as the ground thaws.

Plants that have been weakened during the winter will be less equipped to survive a droughty summer. These plants should receive supplemental summer irrigation.

Winter plant care involves thinking ahead, selecting the appropriate plants for a given site and then taking steps to keep those plants hydrated and minimize injury to them above and below ground. What your clients see in their landscapes come spring should confirm that they’ve chosen the right company.

Philip Meeks is an educator in the areas of natural resources, agriculture and horticulture. He resides in the mountains of southwest Virginia and can be reached at pmeeks@vt.edu.