Last spring frostMay 7
Transplant outApr 23
First harvestOct 23
Last harvestOct 13
First fall frostOct 13
Why these dates work in zone 4a
Zone 4a's last spring frost averages May 7 and first fall frost Oct 13 — about 159 frost-free days. Rhubarb tolerates light frost, so you can set plants out ahead of the last-frost date and keep harvesting into the cooler fall.
Common questions
How long does rhubarb take to grow in zone 4a?
Rhubarb matures in about 548–730 days from transplanting. In zone 4a that means setting plants out around Apr 23 and first picking around Oct 23.
Will rhubarb survive frost in zone 4a?
Yes — rhubarb tolerates light frost. In zone 4a you can set plants out a little before the last frost (around May 7) and keep harvesting past the first fall frost (around Oct 13).
For soil, spacing, pests and companion planting, see the full rhubarb growing guide →