Cold hardiness & minimum temperature

Is Round-leafed Stephania (Stephania rotunda)cold hardy? Hardiness zone & min temp

Also called Round-leafed Stephania.

More about round-leafed stephania

About Round-leafed Stephania

Stephania rotunda · also called Round-leafed Stephania · houseplant

Stephania rotunda is a large-caudex vine from Southeast Asian forests, prized in cultivation for its prominent peltate, rounded leaves and impressive tuberous base. A collector's specimen requiring warmth, moderate humidity during growth, and a completely dry winter dormancy. Not for beginners, but rewarding for patient growers.

Cold limit: USDA 11-12 · RHS H1a (18–35°C)

Watch for — Caudex rot during dormancy: Keeping the soil moist while the plant is leafless is the primary cause of loss. Rot begins at the base and spreads rapidly. Enforce a strict dry rest from autumn leaf drop until spring bud break, and store in a frost-free, dry location.

What round-leafed stephania's hardiness rating actually means

Round-leafed Stephania 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 H1a means: Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever. On the US scale that maps to USDA 11-12 — 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 above about 15 °C (warm, never cold). Round-leafed Stephania has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for round-leafed stephania as it gets too cold:

Below about above about 15 °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 round-leafed stephania go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above above 15 °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 round-leafed stephania can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Round-leafed Stephania hardiness — frequently asked questions

Is round-leafed stephania cold hardy?

Round-leafed Stephania 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. Round-leafed Stephania can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature round-leafed stephania can survive?

Minimum survivable temperature is roughly above about 15 °C (warm, never cold). Round-leafed Stephania has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is round-leafed stephania?

Round-leafed Stephania is rated USDA 11-12 and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can round-leafed stephania survive winter outside?

It can holiday outdoors in summer once nights are reliably above above 15 °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 round-leafed stephania below its minimum temperature?

Below about above about 15 °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.