Cold hardiness & minimum temperature

Is Window Plant (Fenestaria rhopalophylla)cold hardy? Hardiness zone & min temp

Also called Window Plant, Baby Toes, White Baby Toes.

More about window plant

About Window Plant

Fenestaria rhopalophylla · also called Window Plant, Baby Toes · houseplant

Fenestaria rhopalophylla is the white-flowered counterpart to orange Baby Toes, producing dense clumps of club-shaped leaves with translucent, flat-topped windows. Native to Namibian desert sands, it photosynthesises below ground via internal light channels. White daisy flowers appear in autumn. It needs maximum sun and very infrequent water.

Cold limit: USDA 10-12 · RHS H1c (7–32°C)

What window plant's hardiness rating actually means

Window 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). Window Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Window Plant hardiness — frequently asked questions

Is window plant cold hardy?

Window 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. Window 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 window plant can survive?

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

What hardiness zone is window plant?

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

Can window 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 window 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.