Treasure Valley lawn guide
Best grass seed for Treasure Valley lawns
The Treasure Valley is a cool-season grass region. University of Idaho Extension lists Kentucky bluegrass, perennial ryegrass, tall fescue and fine fescues as common lawn choices. The best seed depends on sun, traffic and how much water you want to use.
Kentucky bluegrass
The classic Idaho lawn. It spreads by rhizomes and repairs itself, and it can go dormant through drought if it hardens off first. It needs medium-to-high water and 2 to 5 lb of nitrogen per 1,000 sq ft per season (University of Idaho Extension).
Tall fescue
Deep roots make turf-type tall fescue a good pick for lower-water lawns and hot, sunny exposures. It's clump-forming, so it needs overseeding to fill bare spots.
Perennial ryegrass
Germinates fast (often within about a week, estimate) and is commonly blended with bluegrass for quick cover and wear tolerance.
Fine fescues
Best for shade and low-input areas, but they don't handle heavy traffic well.
When to seed
- Late August through mid-September is the prime window in the valley (estimate): warm soil, cooling air, fewer weeds.
- Spring seeding works but competes with crabgrass and summer heat.
- Aerate first and keep the seedbed consistently moist until seedlings are established.
Common questions
What grass grows best in alkaline Treasure Valley soil?
Kentucky bluegrass and tall fescue both perform well. Yellowing on high-pH soil is often iron chlorosis, which iron chelates help correct (University of Idaho Extension CIS 846).
Can I overseed bluegrass with tall fescue?
You can, but the textures look different. A bluegrass and perennial ryegrass blend keeps a more uniform look.
Related LawnWise guides
Sources
- University of Idaho Extension — Lawn and turf
- University of Idaho Extension CIS 846 — Southern Idaho Fertilizer Guide: Southern Idaho Lawns
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.