Cold hardiness & minimum temperature

Is Wallich's Begonia (Begonia wallichiana)cold hardy? Hardiness zone & min temp

Also called Wallich's begonia, Himalayan begonia.

More about wallich's begonia

About Wallich's Begonia

Begonia wallichiana · also called Wallich's begonia, Himalayan begonia · houseplant

Begonia wallichiana is a species native to the Himalayan foothills of northern India, Nepal, and Bhutan, where it grows in shaded, moist forest understories. It produces clusters of pale pink to white flowers on arching stems and performs best in bright indirect light with consistently moist but well-drained soil. The most important care note is to avoid waterlogging, as the fleshy rhizomes rot quickly in standing moisture. Toxic to cats and dogs per the ASPCA.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (13–24 °C)

Watch for — Vine weevil: Larvae attack the rhizome from beneath the soil surface, causing sudden wilting; inspect the root zone in autumn and treat with nematodes (Steinernema kraussei) when soil temperature allows.

What wallich's begonia's hardiness rating actually means

Wallich's 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). Wallich's Begonia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Wallich's Begonia hardiness — frequently asked questions

Is wallich's begonia cold hardy?

Wallich's 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. Wallich's 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 wallich's begonia can survive?

What hardiness zone is wallich's begonia?

Wallich's 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 wallich's 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 wallich's 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.