Zone 9a covers 32 days of last-frost dates. We measured Mobile, AL at Feb 3 and Seattle, WA at Mar 7. 1 of the 10 places we checked in this zone doesn't dependably freeze at all. Give us your town or ZIP and we'll use ten years of daily lows recorded at your own coordinates instead of the middle of that range.
Why these dates work in zone 9a
Zone 9a's last spring frost averages Feb 12 and first fall frost Dec 3 — about 294 frost-free days. Basil is frost-sensitive, so the 2w after frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost. Starting seeds indoors 4 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does basil take to grow in zone 9a?
Basil matures in about 25–35 days from sowing. In zone 9a that means sowing around Feb 26 and first picking around Mar 23.
Will basil survive frost in zone 9a?
No — basil is frost-sensitive. In zone 9a, wait until after the last frost (around Feb 12) to plant, and harvest before the first fall frost (around Dec 3).
For soil, spacing, pests and companion planting, see the full basil growing guide →