Why does my lawn develop brown patches every spring in New Brunswick?

Spring brown patches in New Brunswick lawns are most commonly caused by snow mould, a fungal disease that develops under prolonged snow cover during the province's long winters. With 250-300cm of average annual snowfall and snow sitting on lawns from December through March or April, conditions are perfect for two types of snow mould: grey snow mould (Typhula blight) and pink snow mould (Microdochium patch). Both thrive in the dark, moist environment beneath snowpack.

Grey snow mould appears as circular patches 6-24 inches in diameter with a greyish-white web of fungal mycelium visible as the snow recedes. Pink snow mould produces similar-sized patches but with a pinkish or salmon-colored tinge to the matted grass. The good news is that grey snow mould typically only kills the leaf blades, not the crown, so most affected areas recover on their own within 3-4 weeks of snowmelt as new growth emerges. Pink snow mould can be more destructive, sometimes killing the crown and requiring reseeding.

Other common causes of spring brown patches in New Brunswick include ice encasement and salt damage. Ice encasement occurs when mid-winter thaws followed by refreezing create a solid ice layer over the grass, suffocating it over weeks or months. This is particularly common in low-lying areas of Fredericton and Moncton yards where water collects during thaws. Salt damage from winter road salt and sidewalk de-icers creates brown, dead strips along driveways and walkways — a familiar sight across every NB city by April.

Vole damage is another frequent culprit that homeowners often mistake for disease. Voles create winding surface tunnels under snow cover, chewing grass down to the crown level. These appear as narrow, serpentine trails of dead grass once snow melts. Heavily affected lawns in rural and suburban Fredericton and Saint John areas may look devastated in April but often recover substantially by mid-June with proper care.

To help your lawn recover from spring brown patches, begin by gently raking affected areas once the soil is dry enough to walk on without leaving footprints. This removes matted dead grass, improves air circulation, and breaks up fungal mycelium. Do not rake aggressively on wet spring soil — you'll damage recovering crowns and compact the soil further. Wait until late May when soil temperatures reach 10°C, then assess which patches are recovering and which need reseeding.

To prevent brown patches next spring, mow your lawn to 2.5 inches for the final fall cut (long grass traps moisture under snow), avoid piling snow on lawn areas when shoveling, apply a fall fungicide in November if snow mould is a recurring problem, and improve drainage in low-lying areas. If brown patches persist year after year in the same spots, the underlying issue may be poor drainage or heavy clay compaction — problems worth addressing with core aeration and soil amendment.

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