The Oregon Lawn Care Calendar, Month by Month
A month-by-month look at Oregon lawn care, covering both cool-season and warm-season grasses, Portland’s frost dates, and the trade-offs of each choice.
Gardening in Oregon
Everything we have worked out for Oregon: what to plant and when, which varieties finish in time, the pests that actually turn up here, and the jobs that pay off month by month. We also cover the rest of the property, from lawns and soil to home care and energy, because a garden rarely stops at the vegetable bed.
The numbers first, because everything else follows from them. Measured at the weather station in Portland, the last spring freeze runs March 6 to March 21 and the first fall freeze runs November 11 to November 27, USDA zones 4a-9b, 2,942 growing degree days in the year.
Garlic does well: 17.4 weeks below 40 °F, comfortably past the six it needs to form a proper head.
Elsewhere on the property in Oregon: the pests that turn up here.
Figures from NOAA's 1991-2020 climate normals. A state is not one climate: elevation, a large lake or the coast can move these dates by two weeks either way, so check your own county with the extension service before you spend money.
Imported cabbageworm in Oregon: When It Shows Up and What Stops It
Small white butterflies fluttering over your broccoli patch in May aren’t just pretty garden visitors.
Slugs in Oregon: When It Shows Up and What Stops It
Slugs show up in Oregon almost year-round, but they hit hardest during the wet, mild stretches of fall (September through November) and again in spring…
Aphids in Oregon: When It Shows Up and What Stops It
Aphids show up in Oregon as soon as daytime temperatures hold above 50°F for a stretch, which usually means late March in the Willamette Valley…
Cucumber beetles in Oregon: When It Shows Up and What Stops It
Cucumber beetles typically show up in Oregon gardens from mid-May through June, once soil temperatures climb past 55°F and cucurbit seedlings break ground.
European earwig in Oregon: When It Shows Up and What Stops It
European earwigs turn up in Oregon lawns, patios, and garden beds from late spring through early fall, with populations peaking in July and August when…
Carrot rust fly in Oregon: When It Shows Up and What Stops It
Carrot rust fly shows up in Oregon gardens in two waves each year, roughly April through June and again in August through September, with timing shifting…
Brown marmorated stink bug in Oregon: When It Shows Up and What Stops It
Brown marmorated stink bugs start showing up in Oregon homes every September and October, right when nighttime temperatures drop into the 40s.
Cabbage maggot in Oregon: When It Shows Up and What Stops It
Cabbage maggot (Delia radicum) hits Oregon brassica crops hardest in the cool, damp regions west of the Cascades, with two active flight periods each…
Garden Pests in Oregon: What Shows Up, When, and How to Stop It
A season-by-season look at the ten pests Oregon State University Extension flags for home gardens, with identification, timing, and real control costs.