Oregon · zones 6a–9a
When to plant basil in Oregon.
Sow or transplant between May 6 to Jul 22 in a typical year, keyed to Oregon's median last frost around Apr 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Basil dates for a typical Oregon season.
1 · Start indoors
Mar 25 to Jun 10
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
May 6 to Jul 22
Keyed to the ~Apr 15 last frost. Sow 0.25" deep, 8" apart.
Harvest
~40 days later
~0.5 lb per plant over ~12 weeks.
Oregon spans more than one climate: Zone 8 is the most common zone, but the state runs 6a to 9a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Oregon growing notes
Basil is transplanted here rather than seeded straight into the garden, and that single choice says most about how little patience this herb has for cold, damp spring soil.
Why this herb skips direct seeding when beans and corn do not
Cold, damp spring soil is exactly what rots a seed this small before it ever pushes through, which is why basil goes into the garden here only as a transplant, never direct-seeded the way beans or corn are. Started indoors instead and moved out once spring frost risk has passed, the plant gets a head start it would not get germinating straight in the ground.
Seed started indoors wants barely a quarter inch of soil over it; any deeper in a cool tray and a seed this small can run out of stored energy before it reaches daylight. Transplants then go in 8 inches apart, closer than nearly any other transplanted crop here, which suits a plant grown to be cut back hard and often rather than left to grow tall and single-stemmed. Left alone, a basil plant eventually sends up a flower spike, and the leaves nearest that spike turn smaller and more bitter as the plant redirects its energy toward seed instead of leaf; pinching that spike off as soon as it appears keeps a plant productive across its 40 days instead of past its best within weeks.
Telling a chilly night from a fungus that looks similar at first
A run of cool nights leaves its own mark on this plant, worth learning to recognize since it is not a disease and no product in the shed treats it. Watch the lowest, oldest leaves first: a grayish-black, water-soaked patch spreading across one of them after a cold night is chill damage, not infection, and the only real fix is warmth and time, not a spray.
Downy mildew can look confusing next to that at first glance, since it also starts with a subtle change on the leaf, yellow patches boxed in by the leaf veins on top, easy to mistake for a nutrient problem before you know to look further. The test that separates the two is flipping the leaf over: downy mildew leaves a grayish to purplish fuzz on the underside directly beneath each yellow patch, visible most clearly in the early morning, while chill damage shows nothing on the underside. Powdery mildew is the easier call, a dusty white coating sitting on top of leaves and stems that looks like flour rather than fuzz.
Mites you can shake onto a sheet of paper, beetles that call in company, and half a pound that comes back in flushes
Spider mites are close to invisible until the damage is well underway, a fine stippling or bronze cast across leaves that have lost their deep green shine, with faint webbing between stems in a heavy infestation. The test that confirms them without a hand lens is simple: hold a sheet of white paper under a suspect branch and tap it hard once. Ordinary dust does not move on its own; mites do, a scatter of tiny specks crawling across the page. Aphids cluster on the newest growth at the tip of each stem, and on a plant this small and this often pinched back, running a thumb and finger up the stem to squeeze them off is usually faster than reaching for a hose.
Japanese beetles rarely arrive one at a time. A leaf that has been chewed gives off a scent that draws more beetles to the plant, so a couple of chewed leaves in the morning can turn into a crowded one by afternoon if the first arrivals are not knocked into a cup of soapy water early. A plant that gets past mites, aphids, beetles, and both fungal problems only needs to hold on for 40 days, and because basil is cut rather than pulled, its half pound of yield does not arrive all at once; it comes back in flushes every time the plant is harvested and pinched back.
In Oregon: watch for
The pests that find basil here.
A middle-length season, about 193 frost-free days, means basil overlaps aphids for a stretch each summer. Check plants every week or two and treat early.
Fine webbing and pale stippling in hot, dry spells.
Organic fix: Spray the undersides with water, then insecticidal soap or neem.
Yellowing with gray fuzz underneath, or white powder on top.
Organic fix: Space for airflow, water at the base, spray neem.
Metallic beetles chewing basil and mint leaves to lace.
Organic fix: Handpick into soapy water in the morning; neem.
Your season math: Oregon gives basil about 193 frost-free days, and it needs roughly 40 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting basil in Oregon: questions
When should I plant basil in Oregon?+
In a typical Oregon year, sow basil or set out transplants between May 6 to Jul 22, keyed to the state's median last frost around Apr 15. Your exact dates shift with your ZIP code and microclimate.
When do I start basil seeds indoors in Oregon?+
Start seeds inside about 6 weeks before set-out: roughly Mar 25 to Jun 10 for a typical Oregon season.
What USDA zone is Oregon?+
Oregon spans zones 6a–9a, mostly zone 8. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many basil plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.