Zone 9b covers 17 days of last-frost dates. We measured Las Vegas, NV at Feb 6 and Sacramento, CA at Feb 23. 10 of the 15 places we checked in this zone don'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 9b
Zone 9b's last spring frost averages Feb 9 and first fall frost Dec 8 — about 302 frost-free days. Sweet Potato is frost-sensitive, so the 3w after frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost.
Common questions
How long does sweet potato take to grow in zone 9b?
Sweet Potato matures in about 90–120 days from transplanting. In zone 9b that means setting plants out around Mar 2 and first picking around May 31.
Will sweet potato survive frost in zone 9b?
No — sweet potato is frost-sensitive. In zone 9b, wait until after the last frost (around Feb 9) to plant, and harvest before the first fall frost (around Dec 8).
For soil, spacing, pests and companion planting, see the full sweet potato growing guide →