Cold hardiness & minimum temperature

Is Wulfen's Alyssum (Alyssum wulfenianum)cold hardy? Hardiness zone & min temp

Also called Wulfen's Alyssum, Wulfenia Alyssum.

More about wulfen's alyssum

About Wulfen's Alyssum

Alyssum wulfenianum · also called Wulfen's Alyssum, Wulfenia Alyssum · flowering

Wulfen's Alyssum is a rare, tufted alpine perennial from the eastern Alps and Dinaric mountains, forming a tight silver-grey cushion. It bears dense clusters of golden-yellow flowers in late spring, releasing a light honey fragrance. A choice plant for specialist rock gardens, alpine troughs, and scree beds, it demands exceptional drainage and full sun.

Cold limit: USDA 4–8 · RHS H7 (-20 to 25°C)

Watch for — Winter wet rot: The most serious risk. Excess moisture in winter will rot the crown and roots rapidly. Grow in an alpine house or under a glass pane from autumn to spring, or site in a raised scree bed with perfect drainage.

What wulfen's alyssum's hardiness rating actually means

Yes — wulfen's alyssum 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. Wulfen's Alyssum is built for winter — once established it takes hard frost and snow in its stride.

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

Wulfen's Alyssum hardiness — frequently asked questions

Is wulfen's alyssum cold hardy?

Yes — wulfen's alyssum 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. Wulfen's Alyssum 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 wulfen's alyssum can survive?

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

What hardiness zone is wulfen's alyssum?

Wulfen's Alyssum is rated USDA 4–8 and RHS H7 — Hardy in the severest European continental winters.

Can wulfen's alyssum 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 wulfen's alyssum 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.