Washington · zones 6b–9a
When to plant basil in Washington.
Sow or transplant between May 5 to Jul 21 in a typical year, keyed to Washington's median last frost around Apr 14. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Basil dates for a typical Washington season.
1 · Start indoors
Mar 24 to Jun 9
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
May 5 to Jul 21
Keyed to the ~Apr 14 last frost. Sow 0.25" deep, 8" apart.
Harvest
~40 days later
~0.5 lb per plant over ~12 weeks.
Washington spans more than one climate: Zone 8 is the most common zone, but the state runs 6b 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.
In Washington: watch for
The pests that find basil here.
A middle-length season, about 187 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: Washington gives basil about 187 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 Washington: questions
When should I plant basil in Washington?+
In a typical Washington year, sow basil or set out transplants between May 5 to Jul 21, keyed to the state's median last frost around Apr 14. Your exact dates shift with your ZIP code and microclimate.
When do I start basil seeds indoors in Washington?+
Start seeds inside about 6 weeks before set-out: roughly Mar 24 to Jun 9 for a typical Washington season.
What USDA zone is Washington?+
Washington spans zones 6b–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.