Cold hardiness & minimum temperature

Is Streptocarpus 'Black Panther' (Streptocarpus 'Black Panther')cold hardy? Hardiness zone & min temp

Also called Black Panther Cape primrose, dark Cape primrose.

More about streptocarpus 'black panther'

About Streptocarpus 'Black Panther'

Streptocarpus 'Black Panther' · also called Black Panther Cape primrose, dark Cape primrose · flowering

A striking Cape primrose cultivar grown for its deep, velvety dark-purple to near-black flowers held on slender stalks above a rosette of long textured leaves. 'Black Panther' flowers freely through the warmer months indoors. Like other Streptocarpus, it is an easy-going gesneriad that wants bright indirect light, careful watering and is safe around pets.

Cold limit: USDA 10-11 (indoor in most US homes) · RHS H1c (15-24°C)

Watch for — Overwatering and root rot: Constantly wet soil rots the fleshy roots and collapses the plant. Let the surface dry between waterings and reduce water sharply in winter.

What streptocarpus 'black panther''s hardiness rating actually means

Streptocarpus 'Black Panther' 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 10-11 (indoor in most US homes) — 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). Streptocarpus 'Black Panther' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Streptocarpus 'Black Panther' hardiness — frequently asked questions

Is streptocarpus 'black panther' cold hardy?

Streptocarpus 'Black Panther' 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. Streptocarpus 'Black Panther' can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature streptocarpus 'black panther' can survive?

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

What hardiness zone is streptocarpus 'black panther'?

Streptocarpus 'Black Panther' is rated USDA 10-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can streptocarpus 'black panther' 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 streptocarpus 'black panther' 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.