When to Plant Grass Seed in Oregon

Cool-season lawns dominate Oregon, and for cool-season seed fall is the better window, with spring the second choice. The dates below are typical crossings from in-state monitoring stations; your city page tracks the live reading.

Best Time to Plant Grass Seed in Oregon

Cool-season · fall window

September 12

September 3 (coolest parts) to September 21 (warmest)

For cool-season lawns (fescue, bluegrass, ryegrass), fall is the best time to plant grass seed in Oregon, with spring the second choice: fall seedlings face less weed competition and mature before summer heat. The window opens as 2-inch soil falls back through 70°F, and germination slows sharply once soil drops below 50°F, typically around November 9. Fall seeding and fall pre-emergent are an either/or on the same turf; see pre-emergent timing in Oregon.

Cool-season · spring window

April 23

March 19 (warmest parts) to April 28 (coolest)

Spring is the second choice: the window opens when soil first holds 50°F and narrows as soil passes 65°F, typically by May 23.

Region	Typical spring window opens	Typical fall window opens	Stations
Eastern Oregon	April 28	September 21	2
Central Oregon	April 23	—	2

Fall seeding also needs a stop date: new seedlings want about six weeks of growth before frost arrives. Your city page estimates the last safe seeding date from its nearest station: see when to plant in Portland, when to plant in Salem or when to plant in Beaverton. Today's statewide reading is on the Oregon soil temperature page.

Typical dates are computed from historical 2-inch soil temperature averages at 4 monitoring stations in Oregon; your own window depends on your nearest station's readings.

Best Time to Plant Grass Seed in Oregon: Month by Month

Typical 2-inch soil temperature by month across Oregon, the median of 4 in-state stations with multi-year records, with the seeding verdict for each grass family. Confirm against the current reading on your city page before you put seed down.

Month	Typical 2" soil temp	Cool-season seeding	Warm-season seeding
January	43°F	Too cold	Too cold
February	43°F	Too cold	Too cold
March	46°F	Too cold	Too cold
April	53°F	Good; fall is better	Too cold
May	63°F	Good; fall is better	Approaching
June	71°F	Risky; heat ahead	Prime window
July	79°F	Too hot	Prime window
August	80°F	Too hot	Prime window
September	70°F	Soon; still cooling	Too late this year
October	58°F	Prime window	Too cold
November	49°F	Too cold	Too cold
December	45°F	Too cold	Too cold