Cold hardiness & minimum temperature

Is Prostrate Raphionacme (Raphionacme procumbens)cold hardy? Hardiness zone & min temp

Also called Prostrate Raphionacme, Raphionacme.

More about prostrate raphionacme

About Prostrate Raphionacme

Raphionacme procumbens · also called Prostrate Raphionacme, Raphionacme · houseplant

A rare South African caudiciform succulent grown for its striking swollen underground caudex, up to 15 cm across. Procumbent annual stems emerge in the growing season and die back in winter. Best kept in bright indirect light with a very free-draining mix; water generously when in growth, then keep almost dry through dormancy.

Cold limit: USDA 9b–11 · RHS H2 (12–30°C)

What prostrate raphionacme's hardiness rating actually means

Prostrate Raphionacme 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 9b–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. Prostrate Raphionacme shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for prostrate raphionacme 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 prostrate raphionacme go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b–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 prostrate raphionacme 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 prostrate raphionacme

Prostrate Raphionacme 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.

Prostrate Raphionacme hardiness — frequently asked questions

Is prostrate raphionacme cold hardy?

Prostrate Raphionacme 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 9b–11 (and sheltered UK gardens) prostrate raphionacme can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature prostrate raphionacme can survive?

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

What hardiness zone is prostrate raphionacme?

Prostrate Raphionacme is rated USDA 9b–11 and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can prostrate raphionacme survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b–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 prostrate raphionacme 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.