Cold hardiness & minimum temperature

Is Wide Eye Plant (Ophthalmophyllum latum)cold hardy? Hardiness zone & min temp

Also called Wide Eye Plant, Broad Ophthalmophyllum.

More about wide eye plant

About Wide Eye Plant

Ophthalmophyllum latum · also called Wide Eye Plant, Broad Ophthalmophyllum · houseplant

Ophthalmophyllum latum is a miniature South African mesemb with notably broad, flat-topped fused leaf pairs whose large translucent windows give the plant its 'wide eye' name. White to pale pink flowers emerge in autumn. Like all ophthalmophyllums, it demands maximum sun, desert-dry summers, and barely-there winter watering — a true specialist plant.

Cold limit: USDA 10-12 · RHS H1c (5–28°C)

What wide eye plant's hardiness rating actually means

Wide Eye Plant 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 10-12 — 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). Wide Eye Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for wide eye plant 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 wide eye plant 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 wide eye plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Wide Eye Plant hardiness — frequently asked questions

Is wide eye plant cold hardy?

Wide Eye Plant 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. Wide Eye Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature wide eye plant can survive?

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

What hardiness zone is wide eye plant?

Wide Eye Plant is rated USDA 10-12 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can wide eye plant 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 wide eye plant 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.