Cold hardiness & minimum temperature

Is Argyroderma delaetii (Argyroderma delaetii)cold hardy? Hardiness zone & min temp

Also called silver skin plant, bum plant.

More about argyroderma delaetii

About Argyroderma delaetii

Argyroderma delaetii · also called silver skin plant, bum plant · houseplant

Argyroderma delaetii, nicknamed the bum plant for its smooth, paired silver-green leaves cleft down the middle, is a winter-growing mesemb from the Knersvlakte quartz fields of South Africa. It opens magenta, yellow or white daisy-like flowers from late autumn into winter. It needs very bright light, a pure mineral mix and water timed to its cool-season growth.

Cold limit: USDA 10-11 (indoor in most US homes) · RHS H2 (10-27°C)

Watch for — Summer rot from wrong-season watering: As a winter grower it rots if watered during hot summer dormancy. Keep it dry in summer and water mainly autumn through spring.

What argyroderma delaetii's hardiness rating actually means

Argyroderma delaetii 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 (indoor in most US homes) — 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. Argyroderma delaetii shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for argyroderma delaetii 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 argyroderma delaetii go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 10-11 (indoor in most US homes) 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 argyroderma delaetii 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 argyroderma delaetii

Argyroderma delaetii 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.

Argyroderma delaetii hardiness — frequently asked questions

Is argyroderma delaetii cold hardy?

Argyroderma delaetii 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 (indoor in most US homes) (and sheltered UK gardens) argyroderma delaetii can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature argyroderma delaetii can survive?

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

What hardiness zone is argyroderma delaetii?

Argyroderma delaetii is rated USDA 10-11 (indoor in most US homes) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can argyroderma delaetii survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 10-11 (indoor in most US homes) 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 argyroderma delaetii 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.