Cold hardiness & minimum temperature

Is Moonstones (Pachyphytum oviferum)cold hardy? Hardiness zone & min temp

Also called Moonstones, Moonstone succulent, Pink moonstone, Sugaralmond plant, Sugared-almond plant.

More about moonstones

About Moonstones

Pachyphytum oviferum · also called Moonstones, Moonstone succulent · houseplant

Moonstones (Pachyphytum oviferum) is a compact Mexican succulent prized for plump, pastel, egg-shaped leaves dusted in a powdery wax called farina. Give it bright light, gritty fast-draining soil, and soak-and-dry watering. It is not individually ASPCA-listed, so treat it as mildly toxic and check with your vet.

Cold limit: USDA 10a-11b (18-27C ideal; keep above 7C (RHS H2: 1-5C minimum))

Watch for — Rubbed-off farina: The chalky white bloom on the leaves is a protective wax (sun and water barrier) that does not grow back. Avoid touching, wiping, or misting the leaves, and water at the soil line to keep the frosted look intact.

What moonstones's hardiness rating actually means

Moonstones is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 10a-11b — 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 10 °C (sustained cold below this is damaging). Moonstones has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for moonstones as it gets too cold:

Below about about 10 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can moonstones go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 moonstones can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Moonstones hardiness — frequently asked questions

Is moonstones cold hardy?

Moonstones is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Moonstones can only live outside year-round in genuinely frost-free climates (roughly USDA 10a-11b); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature moonstones can survive?

Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Moonstones has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is moonstones?

Moonstones is rated USDA 10a-11b and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can moonstones survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to moonstones below its minimum temperature?

Below about about 10 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.