Cold hardiness & minimum temperature

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

Also called Yellow Whitlow Grass, Alpine Whitlow Grass, Yellow Whitlowwort.

More about yellow whitlow grass

About Yellow Whitlow Grass

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

Draba aizoides is a compact, cushion-forming semi-evergreen perennial native to limestone rocks and scree in the mountains of central and southern Europe, from Wales to the Balkans. It thrives in full sun with sharply drained, gritty soil and is among the earliest rock garden plants to bloom, producing bright yellow flowers in February through April. The single most important care point is excellent drainage year-round — waterlogged soil, especially in winter, will kill the plant. Neither Draba aizoides nor the genus Draba appears on the ASPCA toxic or non-toxic plant list; as a Brassicaceae member it is not considered a significant toxicological risk, but classify as mildly-toxic out of caution since ASPCA data is absent.

Cold limit: USDA 4-8 · RHS H5 (-25 to 20°C)

Watch for — Crown rot (Pythium / Fusarium): The most common problem; caused by water sitting in the rosette or waterlogged soil in winter. Plant in vertical crevices or raise on gravel to improve drainage and air circulation around the crown.

What yellow whitlow grass's hardiness rating actually means

Yes — yellow whitlow grass is genuinely cold hardy. Rated RHS H5 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold 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 about −15 to −10 °C. Yellow Whitlow Grass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for yellow whitlow grass as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 whitlow grass 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 whitlow grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Yellow Whitlow Grass hardiness — frequently asked questions

Is yellow whitlow grass cold hardy?

Yes — yellow whitlow grass is genuinely cold hardy. Rated RHS H5 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Yellow Whitlow Grass 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 whitlow grass can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Yellow Whitlow Grass is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is yellow whitlow grass?

Yellow Whitlow Grass is rated USDA 4-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can yellow whitlow grass 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 whitlow grass below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.