Cold hardiness & minimum temperature

Is Common Ice Plant (Mesembryanthemum crystallinum)cold hardy? Hardiness zone & min temp

Also called Common ice plant, Crystalline ice plant, Iceplant.

More about common ice plant

About Common Ice Plant

Mesembryanthemum crystallinum · also called Common ice plant, Crystalline ice plant · edible

Mesembryanthemum crystallinum is an annual or biennial native to the Mediterranean, Middle East, and southern Africa, naturalised along coastal areas worldwide. Its leaves and stems are covered with large glistening vesicles that resemble ice crystals and have a pleasantly salty, succulent taste, making the plant a valued edible green in coastal cuisines. It demands full sun, very free-draining soil, and tolerates salt, drought, and coastal spray, but will rot quickly in waterlogged conditions. The ASPCA does not list it as toxic to cats or dogs; it is considered non-toxic, though very high consumption of the foliage could cause mild digestive upset due to oxalate content.

Cold limit: USDA 9-11 · RHS H2 (5–35°C)

What common ice plant's hardiness rating actually means

Hardiness works differently for common ice plant: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". 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 9-11 — 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

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for common ice plant as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can common ice plant go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

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 common ice plant 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 common ice plant

Common Ice Plant is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Common Ice Plant hardiness — frequently asked questions

Is common ice plant cold hardy?

Hardiness works differently for common ice plant: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Common Ice Plant is grown as an annual in USDA 9-11; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature common ice plant can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is common ice plant?

Common Ice Plant is rated USDA 9-11 and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can common ice plant survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect common ice plant from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.