Cold hardiness & minimum temperature

Is Round-leaf Cape Primrose (Streptocarpus rotundifolius)cold hardy? Hardiness zone & min temp

Also called Round-leaf Cape Primrose, Cape Primrose.

More about round-leaf cape primrose

About Round-leaf Cape Primrose

Streptocarpus rotundifolius · also called Round-leaf Cape Primrose, Cape Primrose · houseplant

Streptocarpus rotundifolius is a unifoliate (single-leaf) species native to shaded, rocky habitats in southern Africa, in the family Gesneriaceae. Its common name reflects its distinctively rounded leaf, which is a continuous-growing macrocotyledon typical of unifoliate Streptocarpus. It thrives in bright, indirect light with moderate moisture and good drainage, and dislikes direct sun or waterlogged compost. The most critical care rule is to keep the soil barely moist and never let water pool in the crown of the leaf. According to the ASPCA, the Streptocarpus genus (Cape Primrose) is non-toxic to cats, dogs, and horses.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1c (15–24°C)

What round-leaf cape primrose's hardiness rating actually means

Round-leaf Cape Primrose 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 (indoor in most climates) — 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). Round-leaf Cape Primrose has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for round-leaf cape primrose 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 round-leaf cape primrose 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 round-leaf cape primrose can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Round-leaf Cape Primrose hardiness — frequently asked questions

Is round-leaf cape primrose cold hardy?

Round-leaf Cape Primrose 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-leaf Cape Primrose can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature round-leaf cape primrose can survive?

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

What hardiness zone is round-leaf cape primrose?

Round-leaf Cape Primrose is rated USDA 10-12 (indoor in most climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can round-leaf cape primrose 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 round-leaf cape primrose 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.