Cold hardiness & minimum temperature

Is River Nile Rex Begonia (Begonia 'River Nile')cold hardy? Hardiness zone & min temp

Also called River Nile rex begonia, River Nile begonia.

More about river nile rex begonia

About River Nile Rex Begonia

Begonia 'River Nile' · also called River Nile rex begonia, River Nile begonia · houseplant

Begonia 'River Nile' is a rhizomatous rex-group begonia grown for its spiralling chartreuse to lime-green leaves edged with crinkled dark red-brown margins, resembling a ram's horn at the leaf base. Native to no specific wild origin, it is a garden hybrid demanding bright indirect light, consistent but moderate moisture, and high humidity — never mist the foliage. The single most important care rule is to water at the soil level and let the rhizome dry slightly between waterings to prevent rot. Toxic to cats and dogs.

Cold limit: USDA 10-12 (indoor-only in most climates) · RHS H1b (16-24°C)

Watch for — Brown leaf edges: Usually indicates low humidity or exposure to draughts and cold windowpane air; move to a more sheltered position and raise ambient humidity.

What river nile rex begonia's hardiness rating actually means

River Nile Rex 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-only 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). River Nile Rex Begonia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

River Nile Rex Begonia hardiness — frequently asked questions

Is river nile rex begonia cold hardy?

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

What is the minimum temperature river nile rex begonia can survive?

What hardiness zone is river nile rex begonia?

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

Can river nile rex 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 river nile rex 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.