Cold hardiness & minimum temperature

Is Rhubarb (Rheum rhabarbarum)cold hardy? Hardiness zone & min temp

Also called garden rhubarb, pieplant.

About Rhubarb

Rheum rhabarbarum · also called garden rhubarb, pieplant · edible

Rhubarb is a hardy perennial grown for tart edible stalks used in pies and crumbles. Leaves are toxic — never eaten by people or pets. Plant crowns in rich soil; established clumps crop for 10-15 years. Toxic to pets.

Rhubarb, Rheum rhabarbarum, is a hardy perennial in the buckwheat family native to southern Siberia and long used medicinally in ancient China; grown for its tart leaf stalks.

Wait until the second season to harvest stalks (third if grown from seed) so the crown establishes; promptly cut flower stalks to keep energy in the leaf stalks. Critical safety point: rhubarb LEAF BLADES contain toxic levels of oxalic acid and must never be eaten, only the stalks.

Cold limit: USDA 3-8 · RHS H7 (10-24°C)

Sources: extension.umn.edu, hort.extension.wisc.edu

What rhubarb's hardiness rating actually means

Yes — rhubarb is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-8 — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly below about −20 °C. Rhubarb is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rhubarb as it gets too cold:

It tolerates winter lows to about −20 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can rhubarb go outside or overwinter — and where?

Plant it out within USDA 3-8 and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when rhubarb can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Rhubarb hardiness — frequently asked questions

Is rhubarb cold hardy?

Yes — rhubarb is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rhubarb is hardy across USDA 3-8; it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature rhubarb can survive?

Minimum survivable temperature is roughly below about −20 °C. Rhubarb is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is rhubarb?

Rhubarb is rated USDA 3-8 and RHS H7 — Hardy in the severest European continental winters.

Can rhubarb survive winter outside?

Plant it out within USDA 3-8 and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to rhubarb below its minimum temperature?

It tolerates winter lows to about −20 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.