Cold hardiness & minimum temperature

Is African Violet 'Optimara' (Streptocarpus sect. Saintpaulia 'Optimara')cold hardy? Hardiness zone & min temp

Also called Optimara African violet, miniature African violet.

More about african violet 'optimara'

About African Violet 'Optimara'

Streptocarpus sect. Saintpaulia 'Optimara' · also called Optimara African violet, miniature African violet · flowering

'Optimara' African violets are a popular bred series of Saintpaulia (now placed in Streptocarpus), compact rosettes of fuzzy leaves that bloom nearly year-round in soft light. They reward steady warmth, bright indirect light and careful bottom-watering with clusters of violet, pink or white flowers, and they are reassuringly safe around cats and dogs.

Cold limit: USDA 11-12 (indoor in most US homes) · RHS H1b (18-24°C)

Watch for — Leaf ring spot: Pale rings appear where cold water touched the leaves. Always use tepid water and water from below.

What african violet 'optimara''s hardiness rating actually means

African Violet 'Optimara' 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 (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 10 °C (sustained cold below this is damaging). African Violet 'Optimara' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for african violet 'optimara' 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 'optimara' 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 'optimara' 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 'Optimara' hardiness — frequently asked questions

Is african violet 'optimara' cold hardy?

African Violet 'Optimara' 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 'Optimara' can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature african violet 'optimara' can survive?

What hardiness zone is african violet 'optimara'?

African Violet 'Optimara' is rated USDA 11-12 (indoor in most US homes) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can african violet 'optimara' 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 'optimara' 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.