Why are my cedar hedges turning brown in New Brunswick?

Cedar hedges turning brown in New Brunswick is extremely common and usually results from winter desiccation — a condition where cold, dry winter winds draw moisture from the foliage faster than frozen roots can replace it. This is the number one cause of cedar browning across the province, particularly on the south and southwest-facing sides of hedges that receive the most wind and winter sun exposure. The damage typically appears in late February through April as brown, dry patches on the outer foliage.

Winter desiccation is especially severe in New Brunswick because of the Maritime province's combination of harsh winter winds, bright sun reflecting off snow, and deeply frozen ground that prevents roots from absorbing replacement moisture. Inland areas like Fredericton and Woodstock (Zone 4a-4b) experience this more intensely than milder coastal areas. To prevent it, water your cedars thoroughly in late October and early November before the ground freezes — fully hydrated cedars are far more resistant. Wrapping hedges in burlap (not plastic) on the windward side provides a physical wind barrier, and anti-desiccant sprays applied in November can reduce moisture loss by up to 30%.

Spider mites are the second most common cause of cedar browning in NB, particularly during hot, dry summers. These tiny pests suck moisture from foliage, causing a stippled yellow-brown discoloration that progresses from the interior outward. To test for them, hold a white piece of paper under a branch and shake it vigorously — tiny moving dots confirm their presence. A strong blast from a garden hose every few days can control minor infestations, while horticultural oil sprays are effective for heavier populations.

Root rot from poor drainage is another frequent issue, especially in NB's clay-heavy river valley soils. Cedars need well-drained soil and will develop brown, dying sections if their roots sit in standing water. This is common in low-lying areas of Moncton subdivisions and along the Saint John River valley. If the browning is concentrated at the base and the wood feels soft or spongy, root rot is likely the cause — improving drainage with French drains or regrading may be necessary.

Other causes include salt spray damage (browning on the road-facing side of hedges, common along NB's salted winter roads), cedar leaf miner insects (tiny tunnels visible in affected foliage), and natural interior needle drop in fall, which is normal and not a concern. If browning is limited to under one-third of the hedge, cedars usually recover with proper watering and fertilization in spring. However, if entire branches are brown and brittle with no green growth remaining, those sections will not recover and should be pruned out. For hedges with extensive damage, consult a certified arborist ($150-400 for an assessment) to determine the underlying cause and best treatment plan.

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