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. Rosemary is frost-sensitive, so the around last 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 10 weeks ahead gives strong transplants ready the moment the soil warms.
Common questions
How long does rosemary take to grow in zone 9a?
Rosemary matures in about 80–100 days from transplanting. In zone 9a that means setting plants out around Feb 12 and first picking around May 3.
Will rosemary survive frost in zone 9a?
No — rosemary 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 rosemary growing guide →