Cold hardiness & minimum temperature

Is African violet streptocarpus (Streptocarpus ionanthus)cold hardy? Hardiness zone & min temp

Also called African violet, Kenya violet, Usambara violet.

More about african violet streptocarpus

About African violet streptocarpus

Streptocarpus ionanthus · also called African violet, Kenya violet · houseplant

A compact, evergreen rosette perennial bearing velvety, dark-green leaves and year-round clusters of violet, pink, or white flowers. Thrives on bright indirect light and consistent moderate moisture without wet leaves. One of the easiest flowering houseplants for indoor growing and confirmed pet-safe by ASPCA.

Cold limit: USDA 11–12 · RHS H1b (15–24°C)

What african violet streptocarpus's hardiness rating actually means

African violet streptocarpus 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. 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 about 10 °C (sustained cold below this is damaging). African violet streptocarpus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for african violet streptocarpus as it gets too cold:

Below about about 10 °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 african violet streptocarpus go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 african violet streptocarpus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

African violet streptocarpus hardiness — frequently asked questions

Is african violet streptocarpus cold hardy?

African violet streptocarpus 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. African violet streptocarpus 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 african violet streptocarpus can survive?

What hardiness zone is african violet streptocarpus?

African violet streptocarpus is rated USDA 11–12 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can african violet streptocarpus survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 african violet streptocarpus below its minimum temperature?

Below about about 10 °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.