Cold hardiness & minimum temperature

Is Emei Mountain Begonia (Begonia emeiensis)cold hardy? Hardiness zone & min temp

Also called Emei Mountain begonia, Mount Emei begonia.

More about emei mountain begonia

About Emei Mountain Begonia

Begonia emeiensis · also called Emei Mountain begonia, Mount Emei begonia · tropical

Begonia emeiensis is a tuberous-rooted species endemic to Mount Emei (Emei Shan) in Sichuan Province, China, where it grows in cool, moist, shaded limestone cliff crevices at altitude. It favours cooler temperatures than most begonias and requires excellent drainage combined with consistent moisture during the growing season. Unlike many tropical begonias, it benefits from a distinct winter rest period. All parts are toxic to cats and dogs.

Cold limit: USDA 9-11 (borderline outdoor in sheltered UK microclimates) · RHS H2 (10–22 °C)

Watch for — Tuber rot in winter dormancy: If the dormant tuber is kept too wet during winter, fungal rots quickly destroy it; store dry tubers in barely moist vermiculite at around 10 °C, or keep in a cool, almost-dry pot.

What emei mountain begonia's hardiness rating actually means

Emei Mountain Begonia is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 9-11 (borderline outdoor in sheltered UK microclimates) — 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 1 to 5 °C — tolerates cold but no real frost. Emei Mountain Begonia shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for emei mountain begonia as it gets too cold:

Down to roughly about 1 to 5 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can emei mountain begonia go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (borderline outdoor in sheltered UK microclimates) or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 emei mountain begonia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline emei mountain begonia

Emei Mountain Begonia is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Emei Mountain Begonia hardiness — frequently asked questions

Is emei mountain begonia cold hardy?

Emei Mountain Begonia is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 9-11 (borderline outdoor in sheltered UK microclimates) (and sheltered UK gardens) emei mountain begonia can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature emei mountain begonia can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Emei Mountain Begonia shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is emei mountain begonia?

Emei Mountain Begonia is rated USDA 9-11 (borderline outdoor in sheltered UK microclimates) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can emei mountain begonia survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (borderline outdoor in sheltered UK microclimates) or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect emei mountain begonia from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.