Cold hardiness & minimum temperature

Is Macdougall's Begonia (Begonia macdougallii)cold hardy? Hardiness zone & min temp

Also called Macdougall's begonia.

More about macdougall's begonia

About Macdougall's Begonia

Begonia macdougallii · also called Macdougall's begonia · tropical

Begonia macdougallii is a shrub-like species first collected in 1948 by Thomas MacDougall from a shaded ravine near a stream in the Sierra Madre of Oaxaca, Mexico, at approximately 1,200 m elevation. It is notable in Begonia history for its role in breeding, contributing to hundreds of cultivars after it reached nurseryman Rudolf Ziesenhenne in Santa Barbara in the late 1940s. It produces branching, fibrous-rooted stems with characteristically asymmetric foliage and bears small flowers on upright growth. The species prefers the cool, moist, shaded conditions of its montane Mexican habitat. Begonia is listed as toxic to cats, dogs, and horses by the ASPCA.

Cold limit: USDA 9-11 (indoor in most climates) · RHS H2 (13–25°C)

Watch for — Overwatering and stem base rot: Stems rot at the base when compost stays saturated, particularly in cooler winter temperatures; reduce watering frequency significantly from late autumn and ensure pots have efficient drainage.

What macdougall's begonia's hardiness rating actually means

Macdougall'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 (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 1 to 5 °C — tolerates cold but no real frost. Macdougall's Begonia shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for macdougall'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 macdougall'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 (indoor in most climates) 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 macdougall'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 macdougall's begonia

Macdougall'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.

Macdougall's Begonia hardiness — frequently asked questions

Is macdougall's begonia cold hardy?

Macdougall'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 (indoor in most climates) (and sheltered UK gardens) macdougall'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 macdougall's begonia can survive?

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

What hardiness zone is macdougall's begonia?

Macdougall's Begonia is rated USDA 9-11 (indoor in most climates) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can macdougall's begonia survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (indoor in most climates) 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 macdougall'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.