Protecting Shrubs Over a Montana Winter

What actually damages shrubs in winter?

The University of Minnesota Extension, writing about Minnesota winters, lists the usual culprits: winter sun, wind and cold can bleach and dry out evergreen foliage, damage bark, and injure or kill branches, flower buds and roots; snow and ice can break branches; deicing salt harms plants; and food shortages push rodents and deer to feed on bark, twigs, buds and leaves. Dry conditions going into winter make plant tissue more susceptible to cold damage, especially on evergreens.

Montana State University Extension makes the same point about water. It notes that many trees and shrubs, especially evergreens, are susceptible to winter desiccation, particularly on warm, sunny winter days when they keep losing moisture faster than it can be replaced. Our guide to winter burn on evergreens explains the process in depth. For planning purposes, the job is to send plants into winter well watered, then cut the exposure to wind and sun, and keep the animals and the plow off them.

Which shrubs need protection in Montana?

Not most of them. A well-chosen native or proven hardy shrub in a suitable spot needs little beyond fall water. Protection is for the plants at risk: broadleaf and needled evergreens in exposed spots, new plantings in their first winters, upright evergreens that split under snow, and anything marginally hardy for your site. Minnesota Extension names yew, arborvitae and hemlock as the most susceptible to winter burn, and says damage usually shows on the south, southwest and windward sides.

Before wrapping anything, ask whether the plant is in the right place. Minnesota Extension suggests siting sensitive evergreens on the north or northeast side of a building, out of the wind and winter sun. A shrub that needs a burlap fort every year may be better moved or replaced. Our guide to shrubs for western Montana and our hardiness zone guide can help you choose plants that will not need it.

Does wrapping shrubs in burlap work?

As a windbreak and sun screen, yes. Minnesota Extension's advice is to construct a barrier of burlap or a similar material on the south, southwest and windward sides of evergreens. If a plant has been injured on all sides, it says to enclose it but leave the top open for air and light. In other words, this is a screen around the plant, not a tight wrap against the foliage.

The usual way to build one is to drive three or four stakes around the shrub in fall before the ground freezes and staple burlap to them, leaving some air space around the foliage. Avoid plastic, which traps heat and moisture and offers none of the breathability that makes burlap useful. Screens also need to handle snow and wind, so set stakes firmly and keep them low enough to be stable. Take the screen down in spring as it warms, so the plant is not sitting in a damp, shaded box.

Are anti-desiccant sprays worth using?

Minnesota Extension says anti-desiccants are not effective for protecting evergreen foliage. Those are the waxy sprays often sold in garden centers for this purpose. If you are choosing where to put your effort, put it into watering and screening instead.

The same goes for late-season pruning and feeding. Minnesota Extension says not to prune evergreens after August, because pruning can trigger new foliage growth that will not harden off in time, and to avoid late-summer pruning, fertilizing and overwatering on deciduous plants, since vigorous growth late in the fall is most likely to die back. Save structural work for dormancy; our dormant pruning service does that in the right window.

How should I water shrubs before winter?

Thoroughly, until the ground freezes. MSU Extension's checklist says to water trees and shrubs into the fall, as long as temperatures are above freezing and snow cover is limited. MSU's north central Montana blog adds that conifers in particular should be watered through the fall until the soil freezes, while deciduous plants can be cut back somewhat earlier to help them harden off. Minnesota Extension says that if the fall has been dry, watering heavily before the ground freezes also reduces frost penetration.

In a dry, open winter, keep going. Colorado State University Extension says to water only when air and soil are above 40 degrees with no snow cover, at midday, about once or twice a month in extended dry periods. For shrubs that are mulched, it suggests 5 gallons twice a month for a newly planted shrub, 5 gallons monthly for small established shrubs, and 18 gallons monthly for shrubs over 6 feet, cutting back for precipitation. Our guide to winter watering covers how to do that once the sprinklers are blown out.

Does mulch help shrubs through winter?

Yes, mainly by protecting roots, which Minnesota Extension says are less hardy than stems and do not go fully dormant as quickly. It explains that snow cover and mulch act as insulators, and that moist soil holds more heat than dry soil. It recommends 3 to 4 inches of shredded wood mulch over the roots of new plants, kept about 6 inches from the trunk, and says a 4 to 6 inch layer can prevent frost heaving by keeping soil temperatures more constant.

Mulch matters most when snow is scarce. MSU's checklist recommends leaf litter or straw over perennial beds in parts of Montana with limited snow cover, and our guide to a low-snow winter explains why a thin snowpack is harder on plants. Near the house in fire country, consider the material carefully; our guide to mulch and wildfire covers what to use in the first few feet.

How do I keep snow from breaking shrubs?

Tie up the ones that split. Minnesota Extension says upright evergreens such as arborvitae and juniper are especially vulnerable, and recommends wrapping small ones together or tying the leaders with strips of carpet, strong cloth or nylon stockings about two-thirds of the way up, above the weak crotches. Take the ties off in spring to prevent girdling and to let stems move. Large or multi-stemmed plants may need an arborist to cable main branches together.

After a wet storm, gently brushing snow off with an upward motion helps, but leave ice alone, because bending frozen branches can break them. Keep plants out from under roof slides and clear of the spot where snow gets piled. Our guide to protecting shrubs from snow load and plow spray covers placement in detail, and our guide to winter tree care and snow load covers the larger plants. For the bigger jobs, our ISA Certified Arborist can assess structure.

What about salt and plow spray?

Minnesota Extension explains that salt runoff builds up in the soil and can injure roots, and that spray from traffic and plows can cause severe foliage or stem injury. It suggests not planting where salty runoff collects, clearing snow quickly, using the minimum salt needed, and considering alternatives such as calcium chloride or calcium magnesium acetate. It also says to choose salt-tolerant species near roads and walks, while noting no species is fully tolerant.

A burlap screen on the road or driveway side also blocks some spray. Our guides to how de-icing salt damages plants and salt-tolerant plants for drivesides go further, and our guide to pet-safe ice melt explains what the labels mean. If you have a snow service, tell them which beds matter, and set where snow goes before the season starts.

How do I protect shrubs from deer, rabbits and voles?

Physically, for the most part. Minnesota Extension recommends cylinders of 1/4 inch hardware cloth set about 6 inches from the stem, buried 2 to 3 inches for mice, and reaching 18 to 24 inches above the expected snow line for rabbits. For voles, it says to cut grass and other vegetation short within 2 feet of young plants in late fall. MSU also notes that plant wraps can protect younger plants from hungry herbivores.

Deer are harder. Minnesota Extension says deer fences should be 8 feet high and well built, because deer can clear fences as high as 12 feet with a running start. Where deer are regular visitors, a smaller cage around the plants that matter most and a planting plan built around what deer ignore works best. Our guides to deer browse in winter, vole trails, deer-resistant plants and custom fencing cover the options.

What should I check on shrubs in spring?

Remove screens, ties and wraps as growth resumes, since MSU warns they can restrict growth and collect pests and disease if left. Then wait before pruning. Browned evergreen foliage on the south or windward side is often winter burn, and some affected branches will push new growth from buds that survived. Once new growth shows, prune out what stayed dead, and water if the spring is dry.

We prune, plant, mulch and replace shrubs and handle the fall and spring cleanups around them as part of our landscaping design and fall cleanup work across Missoula and the Bitterroot Valley. Tell us which shrubs you are worried about and we will take a look. This guide is part of our Montana Landscaping, Lawn & Irrigation Guide. Call (406) 215-7319 or request a free estimate.

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