The best time to plant grass seed in Oregon begins in late summer. The hot summer temperatures have lowered, but plenty of warm days remain. Though you can start grass seed in other seasons, it does not grow as well and will require extra care.
The Best Time to Plant
Start your grass seed from August 15 to September 15. The weather conditions are ideal, allowing seeds to germinate and grow quickly. Planting well in advance of first frost lets the grass mature before winter, ensuring its return as an established lawn come spring.
Planting in Summer
Temperatures in the summer are generally higher than the 65- to 80-degree range recommended for starting grass. Seeds will be competing with other plants, with the elements working against them. Water the lawn carefully to prevent drowning or dehydrating the seeds. Use a fertilizer applied with the water hose to minimize burn caused from hot sun and direct fertilizing.
Planting in the Fall and Spring
Seed planted in weather cooler than 65 degrees F will lay dormant on the ground until the soil warms. This makes the seed vulnerable to being blown or washed away. Increase the density of the seed applied and follow with fertilizer. If your lawn is weedy, the Oregon Grass Seed information website recommends treating weeds in the fall and laying your seed the following spring.