Cold hardiness & minimum temperature

Is Elm-Leaf Begonia (Begonia ulmifolia)cold hardy? Hardiness zone & min temp

Also called Elm-leaf begonia, Elm-leaved begonia.

More about elm-leaf begonia

About Elm-Leaf Begonia

Begonia ulmifolia · also called Elm-leaf begonia, Elm-leaved begonia · houseplant

Begonia ulmifolia is a fibrous-rooted, cane-type begonia native to the Caribbean and northern South America, named for its coarsely textured leaves that resemble those of an elm tree. It is a vigorous grower that tolerates a wider range of indoor conditions than many begonias, including slightly lower humidity. Bright indirect light and moderate, even watering promote healthy growth and small white flowers. Toxic to cats and dogs.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (15–28 °C)

Watch for — Leggy, bare canes: Over time the lower stems shed leaves leaving bare canes; cut canes back by a third to a half in late winter to stimulate bushy regrowth from dormant buds.

What elm-leaf begonia's hardiness rating actually means

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

Concretely, for elm-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 elm-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 elm-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.

Elm-Leaf Begonia hardiness — frequently asked questions

Is elm-leaf begonia cold hardy?

Elm-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. Elm-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 elm-leaf begonia can survive?

What hardiness zone is elm-leaf begonia?

Elm-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 elm-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 elm-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.