Cold hardiness & minimum temperature

Is African Violet 'Blue Nile' (Saintpaulia ionantha 'Blue Nile')cold hardy? Hardiness zone & min temp

Also called blue African violet.

More about african violet 'blue nile'

About African Violet 'Blue Nile'

Saintpaulia ionantha 'Blue Nile' · also called blue African violet · flowering

A standard African violet cultivar grown for its full clusters of blue-violet blooms set against a classic rosette of fuzzy green leaves. Reliable and free-flowering, 'Blue Nile' brings cool-toned colour to windowsills almost year-round when given bright indirect light, steady warmth and careful soil-line watering typical of all Saintpaulia.

Cold limit: USDA 11-12 (indoor houseplant) · RHS H1b (18-24°C)

Watch for — Ring spots on leaves: Cold water or droplets on the fuzzy foliage cause pale marks. Water from below with tepid water and keep leaves dry.

What african violet 'blue nile''s hardiness rating actually means

African Violet 'Blue Nile' 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 houseplant) — 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 'Blue Nile' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for african violet 'blue nile' 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 'blue nile' 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 'blue nile' 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 'Blue Nile' hardiness — frequently asked questions

Is african violet 'blue nile' cold hardy?

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

What is the minimum temperature african violet 'blue nile' can survive?

What hardiness zone is african violet 'blue nile'?

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

Can african violet 'blue nile' 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 'blue nile' 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.