WINTER GARDEN GUIDE
Winter Protection for Shrubs and Trees in Canada
Updated August 2026 · Woody plants, not vegetables · Timing by city
Winter protection for shrubs and trees in Canada goes on after the ground freezes, not at the first frost — and those are about six weeks apart. The other half of the answer is that what kills a woody plant over winter is rarely the cold itself. It is drying wind, freeze-thaw, low winter sun on a young trunk, mice under the snow, or road salt. Each has a different fix, and the hardiness zone on the label predicts none of them.
Five Threats, Five Different Fixes
| Threat | What you find in spring | What actually fixes it |
|---|---|---|
| Desiccation | Evergreen brown on the windward and south-west sides | Water deeply until freeze-up; burlap screen on the windy side |
| Frost heave | A new plant sitting proud of the soil, roots exposed | Mulch after the ground freezes, to keep it frozen |
| Sunscald | Split or sunken bark on a young trunk, south-west face | White trunk wrap or a light shade board — not insulation |
| Rodent girdling | A chewed ring of bark at old snow level | Trunk guard on before snow, clearing the snow depth |
| Road salt | Browning on the road side only; buds fail to open | A burlap screen between plant and road; flush the soil in spring |
Quick Answer
Put winter protection on after the ground freezes — roughly six weeks after your average first frost, so late October on the Prairies and into December in southern Ontario. Going on early is the common mistake: it traps warmth, delays hardening off, and gives mice a sheltered place to chew bark all winter. Burlap is a wind and salt screen, not insulation, so it belongs on stakes with air between it and the plant, never wrapped tight. Never use plastic. And check whether your plant needs anything at all — Explorer, Parkland and rugosa roses are hardy to Zone 3 unaided, while a grafted hybrid tea in Zone 5 genuinely needs its crown mounded.
What Actually Kills a Shrub Over Winter
The reason a plant rated for your zone still dies is that a hardiness zone answers one question and winter asks five. The zone tells you whether the tissue can survive your average coldest temperature. It says nothing about wind, sun angle, freeze-thaw cycling, snow cover, rodents or salt — and those are what usually do the damage.
Desiccation — the big one for evergreens
Cedar, boxwood, yew and rhododendron keep their leaves, and leaves keep losing water. On a bright or windy February day the foliage transpires normally while the roots sit in frozen ground and cannot replace a drop. The plant dries out in the middle of winter. You see it as brown foliage on the windward and south-west faces while the sheltered side stays green — and that asymmetry is how you know it was drying and not cold. The fix happens in autumn: water deeply until the ground freezes, and screen anything exposed.
Frost heave — the one that gets new plantings
Repeated freezing and thawing makes soil expand and contract, and over a winter that motion walks a shallow-rooted plant upward until its roots are in open air. Anything planted this year is the candidate, because it has not rooted out yet. The counter-intuitive fix is that mulch works by keeping the ground frozen, not by keeping it warm — which is exactly why it goes on after freeze-up rather than before.
Sunscald — a sunny-day injury, not a cold one
Low winter sun striking a young, smooth, thin-barked trunk — maple, fruit tree, linden — warms that strip of bark well above air temperature. The tissue starts to come out of dormancy, then night arrives and kills it. The damage is a sunken or split patch, and it is on the south-west side essentially every time, because that is where the afternoon sun lands. Reflected glare off snow makes it worse, so the coldest bright winters are the damaging ones. A white spiral wrap or a small board on the sunny side is enough; the point is shade, not warmth.
Rodents — invisible until April
Mice and voles tunnel at the snow surface and eat bark, and a complete ring around a trunk kills the tree outright — there is no repair for a fully girdled stem. You will not see any of it happening. Two things prevent it: a guard on the trunk before the snow, tall enough to clear the snow you actually get, and keeping mulch pulled back from the trunk instead of heaped against it.
Road salt — a Canadian problem with a Canadian pattern
Spray thrown from a road or driveway lands on the near side of a plant and damages the buds it touches; salt washed into the soil damages roots. The tell is one-sided injury facing the road, or buds that simply fail to open in spring on that face. A burlap screen between plant and road stops the spray, and a deep watering once the ground thaws helps flush the soil.
When to Put It On, by City
The most common error in the whole subject is doing this too early. First frost feels like the signal, and it is not. A plant that is still hardening off needs to feel the cold coming; wrapping it in October leaves it soft going into January. Worse, an early wrap creates a dry sheltered cavity at exactly the moment mice are looking for winter quarters, with bark to eat once they move in.
The real signal is the ground freezing. Below are the dates for 15 cities, from Saskatoon earliest to Toronto latest:
| City | Zone | Avg first frost | Protection on |
|---|---|---|---|
| Saskatoon, SK | 3a | Sep 12 | Oct 22 |
| Regina, SK | 3a | Sep 17 | Oct 27 |
| Winnipeg, MB | 3a | Sep 20 | Oct 30 |
| Thunder Bay, ON | 3b | Sep 20 | Oct 30 |
| Calgary, AB | 3b | Sep 21 | Oct 31 |
| Edmonton, AB | 4a | Sep 23 | Nov 2 |
| Fredericton, NB | 5a | Sep 26 | Nov 5 |
| Quebec City, QC | 5a | Sep 28 | Nov 7 |
| Montréal, QC | 5b | Oct 7 | Nov 16 |
| Ottawa, ON | 5a | Oct 12 | Nov 21 |
| St. John's, NL | 5b | Oct 13 | Nov 22 |
| Halifax, NS | 6a | Oct 18 | Nov 27 |
| London, ON | 6a | Oct 18 | Nov 27 |
| Windsor, ON | 7a | Oct 28 | Dec 7 |
| Toronto, ON | 6b | Nov 1 | Dec 11 |
What this table is, and is not. The first-frost column is measured — Environment and Climate Change Canada climate normals for each city. The “protection on” column is not a measurement: it is that date plus six weeks, a rule of thumb for when the ground is normally frozen, and it is the same offset our fall garden countdown uses for mulching perennials, so the tool and this page agree. Treat it as the week to start watching, not a date to act on blind. The ground itself is the real test — if a trowel still goes in, it is too early.
The south coast of BC is deliberately not in that table. Vancouver and Victoria compute to January dates, which is the arithmetic telling you the rule does not apply: on the mild coast the ground often never freezes hard, so there is no freeze-up to wait for and mounding or mulching for insulation is mostly unnecessary. Coastal winter damage is a different list — wet crowns rotting, wind, and salt near the water — and the answer there is drainage and a wind screen, not a warm coat.
Burlap Does One Job, and It Is Not Insulation
Burlap is a screen. It cuts the drying wind that pulls water out of evergreen foliage, and it catches road-salt spray. That is the whole of it. It adds essentially nothing thermally, and once you know that, the right way to use it follows: neither of those jobs requires the fabric to touch the plant.
So the correct form is stakes driven into the ground around the plant with burlap stapled to them, leaving air between fabric and foliage, and left open at the top so the plant still gets light, air and snow. Where the wind or the road comes from one direction, a screen on that side alone is enough — there is no need to enclose anything.
Three ways to wrap badly. Tight against the foliage: every contact point conducts cold, the fabric holds moisture against the stems, and a tight parcel collects snow load until the shrub splits open. Plastic instead of burlap: it does not breathe, so moisture condenses on the bark, and on a sunny winter day a sealed cover heats fast — the exact temperature swing that splits bark. Sealed at the top: a closed bag turns into a warm humid pocket on the first mild day. Screen, do not parcel.
Two things are worth having before the ground freezes, and neither is expensive. A roll of plain burlap on stakes handles the wind and salt screening described above — buy untreated jute rather than anything coated, since the point is that it breathes. Spiral trunk guards handle the other two threats at once: they shade a young trunk from the low winter sun that causes sunscald, and they physically block mice and voles from reaching the bark. Get guards tall enough to clear the snow you actually get, because rodents tunnel at the snow surface, and take them off in spring rather than leaving them on year-round.
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What Each Plant Actually Needs
A good deal of the winter protection that gets done every autumn is not needed, and knowing which is which saves an afternoon and does the plant no harm at all.
| Plant | Needs | Why |
|---|---|---|
| Explorer / Parkland / rugosa roses | Nothing | Bred in Canada, hardy to Zone 3 on their own roots |
| Hybrid tea & grafted roses | Mound the crown 25–30 cm | The graft union is the part that has to survive |
| Cedar hedge, exposed or roadside | Burlap screen + autumn water | Desiccation and salt, not cold |
| Boxwood, young rhododendron | Screen from wind and winter sun | Broadleaf evergreens lose water fastest |
| Young thin-barked trees | Trunk guard | Sunscald and rodents; both stop at the bark |
| Bigleaf hydrangea | Protect the stems, not the roots | Blooms on old wood — the buds are already on the plant |
| Panicle & smooth hydrangea | Nothing | Blooms on new wood; dieback costs nothing |
| Anything planted this year | Mulch after freeze-up | Frost heave, not cold — roots have not spread yet |
| Established hardy shrubs | Nothing | A mature plant in its zone is already equipped |
The rose row is worth dwelling on, because it is the biggest single saving of effort available here. The Explorer and Parkland series were bred by Agriculture Canada precisely so that Canadians would not have to do this, and rugosas are tougher still. If your roses are those, the correct winter protection is none. It is the grafted hybrid teas that need the crown mounded — and bring that soil in from elsewhere in the garden rather than scraping it from around the roots, which just exposes what you are trying to cover. There is more on pruning them the right way round in our guide to pruning roses in Canada, which is a spring job, not a fall one.
Taking It Off Again
Later than instinct suggests, and in stages. The first genuinely warm week of spring is the trap: everything looks finished, and the frosts are not. Wind and salt screens can come off once hard freezes are done, but mounded soil over a rose crown and mulch over a new planting should stay until the ground has thawed and settled. Those were guarding against freeze-thaw and late frost, which are precisely what is still to come.
Work backwards from your own last frost date rather than from how the week feels — the frost calculator gives yours. And take trunk guards off in spring rather than leaving them: kept on year-round they hold moisture against the bark and can girdle the tree themselves as it thickens, which is a sad way to lose one to a device meant to save it.
When does your ground actually freeze?
The fall garden countdown works every autumn job back from your own city's first frost date, including the one this page turns on — mulching after freeze-up.
Check your city's autumn scheduleFrequently Asked Questions
When should I wrap shrubs for winter in Canada?
After the ground freezes, not at the first frost — and the gap between those two is about six weeks. Wrapping early is the common mistake and it does real harm: it traps warmth against the plant, keeps it from hardening off properly, and creates a sheltered dry space that mice and voles move into and spend the winter chewing bark in. As a working rule, protection goes on roughly six weeks after your average first frost date, which lands in late October on the Prairies, mid-to-late November in Montreal and Ottawa, and into December in Toronto and Windsor. On the south coast of BC the ground often never freezes hard and this whole schedule does not apply.
What actually kills shrubs over winter?
Rarely the cold number itself, which is why a plant rated for your zone can still die. The five real killers are: desiccation, where evergreen foliage keeps losing water on a bright windy February day while the roots sit in frozen ground and cannot replace it; frost heave, where repeated freeze-thaw lifts a newly planted perennial or shrub bodily out of the soil and tears its roots; sunscald, where low winter sun warms a young thin-barked trunk on the south-west side until the tissue breaks dormancy and is then killed by nightfall; rodent girdling, where mice and voles chew a complete ring of bark under the snow; and salt spray from a road or driveway. Each of those has a different fix, and choosing the right one matters more than buying more burlap.
Does burlap actually insulate a plant?
No, and treating it as insulation is why so much burlap gets used badly. Burlap is a wind and salt screen. It cuts the drying wind that pulls moisture out of evergreen foliage and it intercepts road-salt spray, and neither of those jobs requires it to touch the plant. In fact wrapping it tight against the foliage makes things worse: contact points conduct cold, the fabric holds moisture against the stems, and a tight wrap collects snow load that can split a shrub open. The correct form is a screen — stakes driven around the plant with burlap stapled to them, leaving air between fabric and foliage, and open at the top.
Should I use plastic to cover shrubs in winter?
No. Plastic is the one material to keep away from a woody plant over winter. It does not breathe, so moisture condenses inside it and sits on the bark; and on a sunny winter day a sealed plastic cover heats up quickly, which is exactly the temperature swing that causes bark splitting and breaks dormancy at the worst possible moment. If you want a wind screen use burlap or landscape fabric on stakes. If you want to hold snow over a low planting, use evergreen boughs. Plastic sheeting belongs on a cold frame, not on a shrub.
Do I need to protect roses in a Canadian winter?
It depends entirely on which rose, and this is the single most useful thing to know before spending an afternoon on it. The Canadian-bred Explorer and Parkland series and the rugosas are hardy to Zone 3 on their own roots and need nothing at all — protecting them is wasted work. Hybrid teas, floribundas and grandifloras are the ones that need help in Zone 5 and colder: mound 25–30 cm of soil or compost over the crown after the ground freezes, brought in from elsewhere in the garden rather than scraped from around the roots. Grafted roses are the vulnerable case because the graft union is the part that must survive.
How do I stop mice and voles from girdling my trees?
A physical barrier, put on before the snow arrives, because once there is snow cover the animals are working where you cannot see them and the damage is usually found in April. Use a spiral plastic trunk guard or a cylinder of hardware cloth around the trunk of any young or thin-barked tree, pushed slightly into the soil and tall enough to clear the expected snow depth — mice tunnel at the snow surface, so a guard that is buried by February protects nothing. Keep mulch pulled back a few centimetres from the trunk itself: a mulch volcano piled against bark is a mouse habitat with a food source built in.
Why do my cedars turn brown in winter?
That is almost always winter desiccation rather than cold damage, and the distinction changes what you should do. On a sunny or windy winter day the foliage keeps transpiring, but the roots are in frozen ground and cannot draw replacement water, so the needles dry out — worst on the windward and south-west sides, which is the giveaway. The fixes are all preventive and happen in autumn: water deeply until the ground freezes, put a burlap screen on the windward side of anything exposed or near a road, and site new cedars out of the worst wind. Do not shear brown foliage off in January; wait until spring, since much of it recovers.
When should I take winter protection off?
In stages, and later than instinct suggests. Wind and salt screens can come off once the hard freezes are done, but mounded soil over a rose crown and mulch over perennials should stay until the ground has thawed and settled — pulling it in the first warm week exposes new growth to the frosts that are still coming, and those late frosts are what the protection was really for. Work backwards from your last frost date rather than from the weather that week. Take trunk guards off in spring too: left on year-round they trap moisture against the bark and can girdle the tree themselves as it thickens.