Cold hardiness & minimum temperature

Is Twisted Aichryson (Aichryson tortuosum)cold hardy? Hardiness zone & min temp

Also called Twisted Aichryson, Twisted House Leek.

More about twisted aichryson

About Twisted Aichryson

Aichryson tortuosum · also called Twisted Aichryson, Twisted House Leek · houseplant

Aichryson tortuosum is a charming small succulent shrublet from the Canary Islands with distinctively twisted, hairy stems and spoon-shaped fleshy leaves. It produces cheerful yellow star-shaped flowers in spring. Easy to grow on a bright windowsill, it needs excellent drainage and a cool winter rest to perform well as a compact, long-lived houseplant.

Cold limit: USDA 10-11 · RHS H2 (8–24°C)

What twisted aichryson's hardiness rating actually means

Twisted Aichryson is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 10-11 — 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 1 to 5 °C — tolerates cold but no real frost. Twisted Aichryson shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for twisted aichryson as it gets too cold:

Down to roughly about 1 to 5 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can twisted aichryson go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 10-11 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 twisted aichryson can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline twisted aichryson

Twisted Aichryson is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Twisted Aichryson hardiness — frequently asked questions

Is twisted aichryson cold hardy?

Twisted Aichryson is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 10-11 (and sheltered UK gardens) twisted aichryson can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature twisted aichryson can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Twisted Aichryson shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is twisted aichryson?

Twisted Aichryson is rated USDA 10-11 and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can twisted aichryson survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 10-11 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect twisted aichryson from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.