What height should I mow Kentucky Bluegrass during NB summer heat?

Mow Kentucky Bluegrass at 3 to 3.5 inches during New Brunswick summer heat, and raise the deck to 4 inches during extended hot, dry spells in July and August. Taller grass blades shade the soil surface, retain moisture, and support deeper root systems — all critical advantages during the warmest months of NB's short growing season.

The most common mowing mistake in New Brunswick is cutting too short. Many homeowners set their mower at 2 inches thinking it looks neater, but this "scalping" exposes the soil to direct sunlight, increases evaporation dramatically, and stresses the crown of the grass plant. During summer heat, short-cut Bluegrass quickly turns brown and goes dormant, while grass maintained at 3-3.5 inches stays green with significantly less supplemental watering.

Follow the one-third rule religiously: never remove more than one-third of the blade length in a single mowing. For a 3-inch mowing height, this means cutting when the grass reaches about 4.5 inches. During the peak growing season in June, this typically means mowing every 5-7 days. In the hotter, drier weeks of July and August, growth slows and you may only need to mow every 7-10 days. In Fredericton's Zone 4b climate, the growing season runs roughly 120-150 days, so your total mowing season typically spans late May through mid-October.

Leave the grass clippings on the lawn. This practice, called grasscycling, returns nitrogen and moisture to the soil and can reduce your fertilizer needs by 20-25% over the season. Clippings from properly timed mowing (following the one-third rule) decompose within days and do not contribute to thatch buildup despite the common myth.

Keep your mower blade sharp — this matters more than most homeowners realize. A dull blade tears grass rather than cutting it cleanly, leaving ragged edges that turn brown and create entry points for fungal diseases. New Brunswick's high Maritime humidity (which promotes diseases like red thread and dollar spot) makes clean cuts even more important. Sharpen your blade at least twice per season, or more frequently if you're mowing a larger property.

As fall approaches and temperatures cool in September, you can gradually lower your mowing height back to 2.5-3 inches. For the final mow of the season — usually late October in most of New Brunswick — cut to 2.5 inches to reduce the risk of snow mould, which thrives under long grass trapped beneath snowpack. Professional weekly mowing service in New Brunswick costs $35-65 per visit, and most services will adjust cutting height seasonally if you ask.

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