Cold hardiness & minimum temperature

Is Lithops (Lithops)cold hardy? Hardiness zone & min temp

Also called living stones, pebble plants, flowering stones.

About Lithops

Lithops · also called living stones, pebble plants · houseplant

Lithops are extreme succulents from southern Africa that look like pebbles, with two fused leaves and one annual flower. They need a very strict watering cycle tied to their growth seasons and are easy to kill by watering at the wrong time. Pet-safe.

Lithops ('living stones') are South African mesemb succulents that mimic surrounding pebbles for camouflage; each plant is a single pair of fused leaves with a central slit housing the meristem, an extreme adaptation to arid quartz and gravel flats.

Very slow-growing and long-lived; it produces just one new leaf pair per year after flowering, and is a tender plant that must be kept dry and frost-free over winter.

Cold limit: USDA 10-11 (indoor-only) · RHS H1c (15-29°C)

Sources: hort.extension.wisc.edu, savvygardening.com

What lithops's hardiness rating actually means

Lithops 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-11 (indoor-only) — 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 5 °C (and never frost). Lithops has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for lithops as it gets too cold:

Below about about 5 °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 lithops go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 lithops can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Lithops hardiness — frequently asked questions

Is lithops cold hardy?

Lithops 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. Lithops can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor-only)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature lithops can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Lithops has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is lithops?

Lithops is rated USDA 10-11 (indoor-only) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can lithops survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 lithops below its minimum temperature?

Below about about 5 °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.