Treasure Valley lawn guide
Boise lawn care schedule, month by month
Most Treasure Valley lawns are cool-season grasses (mainly Kentucky bluegrass, often mixed with perennial ryegrass or tall fescue). They grow hardest in spring and fall and slow down in summer heat. This schedule lines up the big jobs with that rhythm.
March – April: wake-up
- Rake out matted leaves and snow-mold patches once the lawn dries.
- Apply crabgrass pre-emergent before soil warms to about 55°F at 2 inches, often early-to-mid April here (estimate).
- First mow when grass actively grows; keep it at 2 to 3½ inches (University of Idaho Extension).
May – June: build strength
- Light feeding in late May if the lawn is pale; quick-release nitrogen works best while grass is growing fast (CIS 846).
- Start irrigation as rain tapers off; spring needs are about 1 to 1½ inches of water per week (University of Idaho Extension).
- Spot-treat broadleaf weeds while they're actively growing.
July – August: survive the heat
- Mow at the high end of the range to shade roots and save water.
- Water deeply and less often, early in the morning. Summer needs run higher than spring (University of Idaho Extension).
- Skip heavy fertilizer in peak heat; brown patches in a dry spell are often dormancy, not death.
September – October: the most important season
- Core aerate and overseed thin areas in early-to-mid September (estimate for best germination window).
- Feed in early fall; fall nitrogen builds roots and stored food for spring.
- Cut back watering as nights cool, and plan the sprinkler blowout before the first hard freeze.
November – February: rest
- Final mow slightly lower (around 2 to 2½ inches, estimate) and keep leaves off the grass.
- In dry, snowless stretches above freezing, a midday hand-watering of south-facing slopes helps prevent winter desiccation (estimate).
- Stay off frozen turf to avoid crown damage.
Common questions
When should I start mowing in Boise?
When the grass is actively growing and reaches about 3 to 4 inches, usually in April. Keep the mowing height at 2 to 3½ inches, per University of Idaho Extension.
What's the single most important lawn job in the Treasure Valley?
Fall care. Aerating, overseeding and feeding in September and October sets up a thicker, greener lawn the following spring.
Related LawnWise guides
Sources
- University of Idaho Extension — Lawn and turf
- University of Idaho Extension CIS 846 — Southern Idaho Fertilizer Guide: Southern Idaho Lawns
- University of Idaho Extension CIS 1098 — Watering Home Lawns and Landscapes
Figures marked "estimate" are LawnWise rules of thumb for the Treasure Valley, not extension data. Updated 2026-10-30. By LawnWise, from Seljaas & Sons LLC, Middleton, Idaho.