Cold hardiness & minimum temperature

Is Cushion Draba (Draba bruniifolia)cold hardy? Hardiness zone & min temp

Also called Cushion Draba, Brunii-leaved Whitlow Grass.

More about cushion draba

About Cushion Draba

Draba bruniifolia · also called Cushion Draba, Brunii-leaved Whitlow Grass · flowering

Cushion Draba is a tight-mounding alpine perennial from the Caucasus and Turkey, forming dense evergreen cushions of minute hairy rosettes studded with bright yellow flowers in early to mid-spring. A classic rock garden and alpine trough plant, it is fully frost-hardy and thrives in open scree conditions with perfect drainage and full sun.

Cold limit: USDA 3–7 · RHS H7 (-20°C to 20°C)

Watch for — Cushion rot in wet winters: Persistently wet conditions cause fungal rot at the centre of the cushion, which collapses and browns. Improve drainage, apply a gravel collar, and consider growing in an alpine house or covered frame through the wettest months.

What cushion draba's hardiness rating actually means

Yes — cushion draba is genuinely cold hardy. Rated RHS H7 and USDA 3–7, 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 3–7 — 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. Cushion Draba is built for winter — once established it takes hard frost and snow in its stride.

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

Plant it out within USDA 3–7 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 cushion draba can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Cushion Draba hardiness — frequently asked questions

Is cushion draba cold hardy?

Yes — cushion draba is genuinely cold hardy. Rated RHS H7 and USDA 3–7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Cushion Draba is hardy across USDA 3–7; 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 cushion draba can survive?

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

What hardiness zone is cushion draba?

Cushion Draba is rated USDA 3–7 and RHS H7 — Hardy in the severest European continental winters.

Can cushion draba survive winter outside?

Plant it out within USDA 3–7 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 cushion 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.