Cold hardiness & minimum temperature

Is Yellow Whitlowgrass (Draba aizoides)cold hardy? Hardiness zone & min temp

Also called Yellow Whitlowgrass, Yellow Whitlow Grass, Aizoon Whitlowgrass.

More about yellow whitlowgrass

About Yellow Whitlowgrass

Draba aizoides · also called Yellow Whitlowgrass, Yellow Whitlow Grass · flowering

Yellow Whitlowgrass is a diminutive alpine perennial native to rocky European mountains, forming tight cushions of stiff, bristle-margined leaves. Bright yellow, four-petalled flowers on short stems appear very early in spring, often among the first alpines to bloom. It excels in troughs, rock crevices, and raised beds with excellent drainage.

Cold limit: USDA 4–8 · RHS H7 (-20–22°C)

Watch for — Crown rot in wet winters: Prolonged winter wet is the primary killer. The tight cushion traps moisture at the collar. Grow in well-drained, sloping positions or in an alpine house during wet winters; always use a grit top-dressing.

What yellow whitlowgrass's hardiness rating actually means

Yes — yellow whitlowgrass 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. Yellow Whitlowgrass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for yellow whitlowgrass 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 yellow whitlowgrass 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 yellow whitlowgrass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Yellow Whitlowgrass hardiness — frequently asked questions

Is yellow whitlowgrass cold hardy?

Yes — yellow whitlowgrass 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. Yellow Whitlowgrass 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 yellow whitlowgrass can survive?

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

What hardiness zone is yellow whitlowgrass?

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

Can yellow whitlowgrass 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 yellow whitlowgrass 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.