Cold hardiness & minimum temperature

Is primrose-leaf cape primrose (Streptocarpus primulifolius)cold hardy? Hardiness zone & min temp

Also called primrose-leaf cape primrose.

More about primrose-leaf cape primrose

About primrose-leaf cape primrose

Streptocarpus primulifolius · also called primrose-leaf cape primrose · houseplant

A fast-growing, shade-tolerant South African perennial with leaves resembling primroses and elegant, deep mauve trumpet flowers streaked with dark purple in summer. Each leaf functions as an individual plant with its own roots and flowering stems. Ideal for shaded windowsills, forest-style terrariums, or sheltered shaded garden spots in mild climates.

Cold limit: USDA 10–11 · RHS H1c (15–24°C)

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

primrose-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 10–11 — 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). primrose-leaf cape primrose has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for primrose-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 primrose-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 primrose-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.

primrose-leaf cape primrose hardiness — frequently asked questions

Is primrose-leaf cape primrose cold hardy?

primrose-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. primrose-leaf cape primrose can only live outside year-round in genuinely frost-free climates (roughly USDA 10–11); everywhere else it is a houseplant that summers out at most.

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

Minimum survivable temperature is roughly about 5 °C (and never frost). primrose-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 primrose-leaf cape primrose?

primrose-leaf cape primrose is rated USDA 10–11 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can primrose-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 primrose-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.