Cold hardiness & minimum temperature

Is Glaskins Perpetual Rhubarb (Rheum × hybridum 'Glaskin's Perpetual')cold hardy? Hardiness zone & min temp

Also called Glaskin's Perpetual rhubarb, seed-grown rhubarb.

More about glaskins perpetual rhubarb

About Glaskins Perpetual Rhubarb

Rheum × hybridum 'Glaskin's Perpetual' · also called Glaskin's Perpetual rhubarb, seed-grown rhubarb · edible

Glaskin's Perpetual is the rhubarb most reliably raised from seed, with a long picking season and low oxalic acid that lets you harvest into late summer. Its green-to-red stalks are pleasantly tart. Grow in full sun and rich, moist soil; a vigorous, fully hardy perennial ideal for impatient gardeners who want a crop fast.

Cold limit: USDA 3-8 · RHS H6 (-20 to 24°C)

Watch for — Crown rot: Waterlogged winter ground rots the crown. Plant on free-draining soil or a mound and keep the crown's centre clear of heavy wet mulch.

What glaskins perpetual rhubarb's hardiness rating actually means

Yes — glaskins perpetual rhubarb is genuinely cold hardy. Rated RHS H6 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. 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 about −20 to −15 °C. Glaskins Perpetual Rhubarb is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for glaskins perpetual rhubarb as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 glaskins perpetual 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 glaskins perpetual rhubarb can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Glaskins Perpetual Rhubarb hardiness — frequently asked questions

Is glaskins perpetual rhubarb cold hardy?

Yes — glaskins perpetual rhubarb is genuinely cold hardy. Rated RHS H6 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Glaskins Perpetual 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 glaskins perpetual rhubarb can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Glaskins Perpetual Rhubarb is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is glaskins perpetual rhubarb?

Glaskins Perpetual Rhubarb is rated USDA 3-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can glaskins perpetual 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 glaskins perpetual rhubarb below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.