Cold hardiness & minimum temperature

Is Reunion Island Begonia (Begonia salaziensis)cold hardy? Hardiness zone & min temp

Also called Reunion Island begonia, Salazie begonia.

More about reunion island begonia

About Reunion Island Begonia

Begonia salaziensis · also called Reunion Island begonia, Salazie begonia · tropical

Begonia salaziensis is a rare fibrous-rooted species endemic to the cloud-forest habitats of Réunion Island in the Indian Ocean, where it grows as an understorey plant in cool, misty conditions. It produces attractive foliage and small pink to white flowers, preferring consistently cool temperatures that distinguish it from most tropical begonias. The single most critical care point is to keep temperatures below 25 °C, as prolonged heat causes rapid decline in this naturally cool-adapted species. This plant is toxic to cats and dogs.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (12–22 °C)

Watch for — Heat stress and leaf scorch: Temperatures above 25 °C cause wilting, yellowing, and leaf edge scorch; move to a cooler, well-ventilated position — ideally below 22 °C — and shade from any direct sun.

What reunion island begonia's hardiness rating actually means

Reunion Island Begonia 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 10-12 (indoor in most climates) — 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). Reunion Island Begonia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for reunion island begonia 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 reunion island begonia 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 reunion island begonia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Reunion Island Begonia hardiness — frequently asked questions

Is reunion island begonia cold hardy?

Reunion Island Begonia 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. Reunion Island Begonia can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature reunion island begonia can survive?

What hardiness zone is reunion island begonia?

Reunion Island Begonia is rated USDA 10-12 (indoor in most climates) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can reunion island begonia 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 reunion island begonia 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.