Zone 6a covers 28 days of last-frost dates. We measured Omaha, NE at Apr 14 and Flagstaff, AZ at May 12. 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 6a
Zone 6a's last spring frost averages Apr 22 and first fall frost Nov 1 — about 193 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 6a?
Rosemary matures in about 80–100 days from transplanting. In zone 6a that means setting plants out around Apr 22 and first picking around Jul 11.
Will rosemary survive frost in zone 6a?
No — rosemary is frost-sensitive. In zone 6a, wait until after the last frost (around Apr 22) to plant, and harvest before the first fall frost (around Nov 1).
For soil, spacing, pests and companion planting, see the full rosemary growing guide →