Cold hardiness & minimum temperature

Is Roxburgh's Begonia (Begonia roxburghii)cold hardy? Hardiness zone & min temp

Also called Roxburgh's begonia, Red-dotted begonia, Himalayan begonia.

More about roxburgh's begonia

About Roxburgh's Begonia

Begonia roxburghii · also called Roxburgh's begonia, Red-dotted begonia · flowering

Begonia roxburghii is a caulescent (stemmed), erect species native to the Eastern Himalayas — northeast India, Nepal, Sikkim, Bangladesh, and Myanmar — growing at elevations between 300 and 1,850 m in forest margins and rocky slopes. Its stout stems reach 60-120 cm and are distinctively marked with red elongated dots or spots; it bears light pinkish-white flowers with yellow stamens. Being from a montane subtropical habitat, it tolerates cooler temperatures than most tropical begonias but still requires protection from frost; the key care point is providing bright indirect light combined with good drainage to replicate its rocky, well-drained native hillside habitat. Begonia roxburghii is toxic to cats, dogs, and horses.

Cold limit: USDA 9-11 (borderline outdoors in mild frost-free regions) · RHS H2 (12-24°C)

Watch for — Stem rot in waterlogged compost: The stout, slightly woody stems rot at the base when compost stays too wet, particularly in winter during the plant's natural cool, drier rest period. Ensure excellent drainage, reduce watering frequency in cool months, and use a free-draining mix.

What roxburgh's begonia's hardiness rating actually means

Roxburgh's 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 outdoors in mild frost-free regions) — 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. Roxburgh's Begonia shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for roxburgh's 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 roxburgh's 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 outdoors in mild frost-free regions) 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 roxburgh's 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 roxburgh's begonia

Roxburgh's 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.

Roxburgh's Begonia hardiness — frequently asked questions

Is roxburgh's begonia cold hardy?

Roxburgh's 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 outdoors in mild frost-free regions) (and sheltered UK gardens) roxburgh's 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 roxburgh's begonia can survive?

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

What hardiness zone is roxburgh's begonia?

Roxburgh's Begonia is rated USDA 9-11 (borderline outdoors in mild frost-free regions) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can roxburgh's begonia survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (borderline outdoors in mild frost-free regions) 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 roxburgh's 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.