If your cedar hedge came out of last winter with brown, brittle patches on one side, the cause was almost certainly not the cold. It was thirst. Winter burn, the browning that shows up on cedars, yews and boxwood every March and April, happens when winter sun and wind pull moisture out of evergreen foliage faster than the roots can replace it, because the soil those roots sit in is frozen solid. The University of Minnesota Extension, whose guidance on the problem was last reviewed in 2026, describes it as desiccation rather than cold injury, and notes that the damage normally appears on the south, southwest and windward sides of a plant, exactly where the low winter sun hits hardest. A second mechanism compounds it: bright, cold days destroy chlorophyll in the foliage, and the plant cannot rebuild it while temperatures sit below about minus two degrees Celsius, which is why burned cedars often look bleached rather than simply dead.
The window to do something about it is now. Nearly every protective step that works has to happen before the ground freezes, and by the time the foliage turns brown in spring the injury is months old. Arborvitae, which is what most Canadians call cedar, sits near the top of the susceptible list along with yew and hemlock, and anything planted within the past year is more vulnerable still. Emerald cedar, the Thuja occidentalis cultivar sold as Smaragd or Brandon and planted by the thousands in Ontario hedges, is particularly demanding, according to the Toronto Master Gardeners, partly because most of the stock is grown in British Columbia and trucked east. The steps below are all ground-level work. If a tree is tall enough that protecting it would mean climbing a ladder, hire an arborist rather than attempting it yourself.
Step 1: Stop pruning
Do not prune evergreens after August. The University of Minnesota Extension is explicit that late pruning induces a flush of new foliage, and soft, unhardened growth heading into November is the tissue most likely to be killed. The same logic applies to late fertilizing and heavy late-season watering, all of which keep a plant growing when it should be shutting down.
Step 2: Ease off water in September, then soak in October
The Extension recommends decreasing watering slightly in September to encourage hardening off, then watering thoroughly through October right up until freeze-up. The timing matters: watering only in late fall, after a dry autumn, does not reduce injury. For emerald cedars specifically, the Toronto Master Gardeners advise a deep, slow watering twice a week until the weather cools and once a week after that, and say plainly not to put the hose away until late November.
Step 3: Soak the ground hard before it freezes
If the fall has been dry, water heavily in the days before freeze-up. Moist soil holds more heat than dry soil, so a well-watered bed freezes less deeply, and roots that go into winter hydrated have something to draw on during a January thaw.
Step 4: Mulch the root zone
Lay 8 to 10 centimetres of shredded bark mulch over the roots of newly planted evergreens, pulling it back about 15 centimetres from the trunk so it forms a donut rather than a volcano. Piling mulch against the stem encourages girdling roots. A deeper layer, 10 to 15 centimetres, guards against frost heaving, the repeated freeze and thaw cycle that can push a new shrub bodily out of the ground. Landscape Ontario suggests applying it ideally after the soil has frozen, and recommends straw about 20 centimetres deep as an alternative where appearance does not matter. Avoid hay, which is full of weed seed.
Step 5: Drive your stakes while the soil is still soft
This is the step people miss. Landscape Ontario advises pounding pointed one-by-two stakes into the ground in fall, while it is still workable, and coming back later to attach the burlap. For a full wrap around an upright cedar, use at least three tall bamboo stakes tied together at the top to form a rough teepee. The stakes exist so the fabric never touches the foliage, which matters: burlap laid directly on wet needles through a mild winter invites mould.
Step 6: Decide between a screen and a full wrap
A screen on the exposed sides is often enough. The Extension recommends a burlap barrier on the south, southwest and windward sides, and says that if a plant showed injury on all sides last year, surround it but leave the top open for air and light. A full wrap makes more sense for a plant that also needs branch support, or one standing alone in open wind. Wrapping is also the accepted defence for anything planted within the past year, broadleaf evergreens such as rhododendron and boxwood, and any shrub close enough to a salted road or sidewalk to catch spray.
Step 7: Wrap once the cold has actually arrived
Sources differ on timing, and the difference is regional rather than contradictory. Prairie growers commonly wrap before the first hard frost, with the day after Halloween cited as a practical marker. Landscape Ontario advises waiting until the cold has genuinely set in, usually November or even early December, and until the ground has frozen. The safe reading is that the stakes go in early and the burlap goes on late, once growth has hardened off, somewhere between late October and early December depending on where you live. Wrap starting at the bottom and spiral upward, using clothes pegs to hold the fabric while you work, then run twine around the top of the frame and spiral back down, tying off at a stake.
Step 8: Use burlap, not plastic
Burlap breathes. Plastic sheeting and solid tarps trap moisture and let the interior overheat on sunny days, which recreates the freeze and thaw stress you are trying to prevent.
Step 9: Tie up globe cedars and multi-stemmed uprights against snow load
Upright arborvitae and juniper are among the plants most likely to bend or split under snow and ice. Tie twine to the base of the trunk and spiral it up the plant, gently drawing the branches in toward the centre. Landscape Ontario stresses that you are not cinching the plant tight, only reducing the surface available to collect snow and supporting the branches if it does. Globe cedars, which split open readily, benefit most. Pay particular attention to any evergreen sitting under a roof drip edge or beside a path you will be shovelling onto.
Step 10: Screen out rabbits and voles at the same time
While the fabric is going up, deal with browsing. The Extension recommends cylinders of six-millimetre hardware cloth set about 15 centimetres out from the trunk, extending 45 to 60 centimetres above the expected snow line for rabbits and two to three centimetres below ground level for mice and voles. Cut long grass within about 60 centimetres of young trees in late fall to remove the cover voles rely on.
Step 11: Skip the anti-desiccant spray
Anti-desiccant and anti-transpirant sprays are widely sold for this exact purpose, and some landscape contractors apply them. The University of Minnesota Extension states flatly that they are not effective for protecting evergreen foliage. The disagreement is worth knowing about before you spend money on one. Watering, siting and a wind barrier are the measures the Extension actually endorses.
Step 12: If burn appears in spring, wait before cutting
Brown foliage is dead and will not green up. The buds, however, are hardier than the leaves and often push new growth that fills the gap. Wait until mid-spring before pruning anything out, then cut back only to living tissue where the buds did not survive. Water the plant well through the following season and protect it again next winter.
None of this is difficult work, and most of it takes an afternoon for a typical hedge. The hard part is the calendar. A cedar that gets watered into late fall, mulched, staked before freeze-up and screened from the southwest wind will usually come through a Canadian winter green. One that gets attention in March will not.
Sources: University of Minnesota Extension, “Protecting trees and shrubs in winter” (reviewed 2026); Landscape Ontario, “Winter protection for delicate plants”; Toronto Master Gardeners, “Winter protection for cedars.”
