September can be a little confusing in the Portland garden. The calendar says fall, but the garden may still feel like summer. After months of dry weather, it is tempting to keep the irrigation running on the same schedule. Don't. 

Portland's rainy season will eventually take over, but there is no magic date when every plant should get its last drink. Watch the weather, check the soil, and adjust as conditions change.

As temperatures cool and fall rains return, gradually reduce both the frequency and amount of irrigation.

Established trees and shrubs generally need much less water as fall progresses. Don't keep automatic irrigation on its summer schedule just because the calendar hasn't caught up yet.

Check the soil before you water. If it is still moist several inches down, wait.

New trees and shrubs need special attention. Their root systems are still developing, so don't assume that the first fall rain means they are established.

Continue watering newly planted trees and shrubs until consistent rainfall arrives. OSU recommends watering new fall plantings about once a week until regular rain begins, with additional water during extended dry periods.

Once we start getting regular Portland rain, turn off the automatic irrigation and let nature take over.

This is particularly important with our heavy clay soils. Constantly wet soil can create drainage problems and contribute to root rot.

For established lawns in the Willamette Valley, OSU recommends stopping irrigation after Labor Day.

Your lawn may start looking a little tired. That's okay. It will recover when the fall rains arrive.

Don't water by the calendar—water by the soil. Stick a finger or small trowel into the soil before turning on the hose. If it's still moist, give the garden a break.

September is the time to start weaning your garden off summer irrigation. By the time the steady rains arrive, your watering schedule should already be winding down.