Cold hardiness & minimum temperature

Is Single-Leaf Begonia (Begonia unifolia)cold hardy? Hardiness zone & min temp

Also called Single-leaf begonia.

More about single-leaf begonia

About Single-Leaf Begonia

Begonia unifolia · also called Single-leaf begonia · houseplant

Begonia unifolia is a small, rarely cultivated species from South America, characterised by its solitary or few leaves arising from a compact stem. Like most begonias in cultivation, it requires warm, humid conditions with bright indirect light and consistently moist but well-drained compost. Because of its compact habit, it is best grown in a terrarium or humid case where moisture levels can be maintained. Toxic to cats and dogs.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (16–26 °C)

What single-leaf begonia's hardiness rating actually means

Single-Leaf 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). Single-Leaf Begonia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Single-Leaf Begonia hardiness — frequently asked questions

Is single-leaf begonia cold hardy?

Single-Leaf 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. Single-Leaf 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 single-leaf begonia can survive?

What hardiness zone is single-leaf begonia?

Single-Leaf 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 single-leaf 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 single-leaf 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.