Cold hardiness & minimum temperature

Is Echeveria harmsii (Echeveria harmsii)cold hardy? Hardiness zone & min temp

Also called Ruby slippers, plush plant.

More about echeveria harmsii

About Echeveria harmsii

Echeveria harmsii · also called Ruby slippers, plush plant · houseplant

Echeveria harmsii, the plush plant or 'Ruby slippers', is a shrubby succulent with branching stems and loose rosettes of velvety, hairy green leaves edged in red. Unlike flat echeverias it grows upright to around 30 cm and produces unusually large red-and-yellow lantern flowers in spring. The soft hairs mean it needs careful base-watering.

Cold limit: USDA 9b-11 (indoor in most US homes) · RHS H2 (18-27°C)

Watch for — Leaf drop: Velvety leaves drop after stress from overwatering, cold draughts or being moved. Stabilise conditions and let the soil dry between waterings.

What echeveria harmsii's hardiness rating actually means

Echeveria harmsii 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 (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. Echeveria harmsii shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for echeveria harmsii 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 echeveria harmsii go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b-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 echeveria harmsii 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 echeveria harmsii

Echeveria harmsii 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.

Echeveria harmsii hardiness — frequently asked questions

Is echeveria harmsii cold hardy?

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

What is the minimum temperature echeveria harmsii can survive?

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

What hardiness zone is echeveria harmsii?

Echeveria harmsii is rated USDA 9b-11 (indoor in most US homes) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can echeveria harmsii survive winter outside?

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