Fruit · Polygonaceae
When to plant rhubarb
Needs a cold winter to break dormancy properly, which makes it one of the few crops that is easier in a harsh climate than a mild one. The leaves are toxic; only the stalks are eaten.
First worthwhile crop
Year 2
After planting, not after sowing.
Hardy in USDA zones
3a to 8a
Winter cold sets the limit here, not the calendar.
Frost tolerance
Very hardy
How much cold the plant itself will take.
Those weeks become real dates once you name a place.
Timing, in frost-relative terms
Nothing about a standing crop is sown to a calendar. Once planted, rhubarb stay in the ground for years, so the question is not when to sow but whether your winter is survivable and your planting window is open. Both answers come from your frost dates.
- Expect a first worthwhile crop in year 2 after planting.
- Needs roughly 500 chill hours below 7.2°C (45°F)45°F (7.2°C) over winter to set fruit, which rules out the warmest climates.
- Hardy in USDA zones 3a–8a.
Getting the timing right
Plant dormant crowns with the buds just at soil level. Take nothing at all in the first year and only lightly in the second - the plant is building a root system, and stripping it early stunts it permanently. After that, pull rather than cut, and stop by midsummer.
Frost tolerance
The crown is entirely hardy and actively wants the cold. Early stalks caught by a hard frost turn limp and should be discarded rather than eaten.
Classified as very-hardy.