What causes winter burn on arborvitae in NB?

Winter burn on arborvitae is caused by desiccation — the foliage loses moisture through transpiration on sunny, windy winter days while the frozen ground prevents the roots from replacing that lost water. It's one of the most common complaints from New Brunswick homeowners, and the good news is it's largely preventable once you understand what's happening.

Arborvitae (Thuja occidentalis) are evergreens, meaning their foliage stays active year-round — even in winter. On a bright February day in Fredericton or Moncton, the sun warms the foliage and triggers moisture loss, while the wind accelerates it. The roots, locked in frozen ground (often 1.2–1.5 metres deep in NB), simply can't draw up replacement water. The result is that characteristic brown, crispy foliage — usually worst on the south and west-facing sides of the plant, and on the windward side in coastal areas like Saint John or Shediac.

The timing in New Brunswick makes this particularly damaging. Our late-season freeze-up (November) combined with intense late-winter sun (February–March) creates a long window of vulnerability. Ice storms — a regular feature of NB winters — compound the problem by coating foliage and adding physical weight stress on top of the desiccation damage. The brown you see in April isn't always from the coldest nights; it's often from those deceptively sunny March days when the ground is still locked solid.

Why Some Properties Are Worse Than Others

Exposed sites, southwest-facing hedges, and properties near roads (where salt spray is a factor) consistently show more winter burn. Arborvitae planted in sandy, fast-draining soils — common in the Miramichi and coastal areas — are also more vulnerable because those soils dry out faster in fall, meaning the plant goes into winter already slightly moisture-stressed.

What You Can Do

Before winter sets in (October): Water deeply and thoroughly before the ground freezes — this is the single most effective prevention step. A well-hydrated plant going into freeze-up handles winter stress dramatically better.

Apply an anti-desiccant spray (sold as Wilt-Pruf or similar) in late November, before hard frost. It forms a waxy coating on the foliage that reduces moisture loss. Reapply in late February if you get a mild day above 5°C.

Burlap wrapping is effective but must be done correctly — wrap loosely around a frame so air still circulates, rather than tight against the foliage. Remove it by mid-April at the latest, before new growth pushes.

Don't prune the brown foliage until late May. What looks dead in April sometimes recovers once roots rehydrate in spring. Wait and see before cutting.

If your arborvitae hedge is in a particularly exposed location and suffering every year, a professional landscaper can assess whether a windbreak planting, relocated burlap screening, or even a species change (White Cedar is more resilient than some cultivars) makes more sense long-term. New Brunswick Landscaping can match you with a local landscaper who knows your specific area's conditions — the fix in Campbellton looks different than in Sussex.