Cold hardiness & minimum temperature

Is Rigid Draba (Draba rigida)cold hardy? Hardiness zone & min temp

Also called Rigid Draba, Stiff Whitlowgrass.

More about rigid draba

About Rigid Draba

Draba rigida · also called Rigid Draba, Stiff Whitlowgrass · flowering

Rigid Draba is a minute cushion alpine from volcanic and rocky habitats in Turkey and the Caucasus, producing remarkably tight, hard domes of tiny, rigid leaves. Cheerful bright yellow flowers appear in early spring on very short stems. It is among the most compact of all alpine drabas and a favourite for specialist alpine troughs and exhibition work.

Cold limit: USDA 4–8 · RHS H7 (-20–20°C)

Watch for — Winter wet rot: The tight, impermeable cushion is extremely prone to rotting from above when exposed to prolonged rainfall. Cultivation under glass in an alpine house or with overhead protection during winter is strongly recommended.

What rigid draba's hardiness rating actually means

Yes — rigid draba is genuinely cold hardy. Rated RHS H7 and USDA 4–8, 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 4–8 — 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. Rigid Draba is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rigid draba 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 rigid draba go outside or overwinter — and where?

Plant it out within USDA 4–8 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 rigid draba can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Rigid Draba hardiness — frequently asked questions

Is rigid draba cold hardy?

Yes — rigid draba is genuinely cold hardy. Rated RHS H7 and USDA 4–8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rigid Draba is hardy across USDA 4–8; 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 rigid draba can survive?

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

What hardiness zone is rigid draba?

Rigid Draba is rated USDA 4–8 and RHS H7 — Hardy in the severest European continental winters.

Can rigid draba survive winter outside?

Plant it out within USDA 4–8 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 rigid draba 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.