Cold hardiness & minimum temperature

Is Holton's Begonia (Begonia holtonis)cold hardy? Hardiness zone & min temp

Also called Holton's begonia.

More about holton's begonia

About Holton's Begonia

Begonia holtonis · also called Holton's begonia · tropical

Begonia holtonis is a compact subshrub native to the Andean forests of Colombia and northwest Venezuela, where it grows at elevations of 1,000–2,300 m in humid montane woodland. First collected by Isaac Farwell Holton in 1857 and formally described by Alphonse de Candolle, it is valued for its attractive small leaves, bushy habit, and white flowers produced from winter through summer. The most important care point is maintaining consistently warm, humid conditions indoors, as the Andean origin means it tolerates slightly cooler temperatures than many tropical begonias but cannot withstand frost. Begonias are toxic to cats, dogs, and horses.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (15–25°C)

What holton's begonia's hardiness rating actually means

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

Concretely, for holton'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 holton'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 holton'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.

Holton's Begonia hardiness — frequently asked questions

Is holton's begonia cold hardy?

Holton'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. Holton'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 holton's begonia can survive?

What hardiness zone is holton's begonia?

Holton'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 holton'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 holton'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.