Cold hardiness & minimum temperature

Is Begonia grandis (Begonia grandis)cold hardy? Hardiness zone & min temp

Also called hardy begonia, Chinese begonia, Evans begonia.

More about begonia grandis

About Begonia grandis

Begonia grandis · also called hardy begonia, Chinese begonia · flowering

Begonia grandis is the only begonia reliably winter-hardy in the open ground, surviving to USDA Zone 6. This tuberous species forms upright, branching stems to 60 cm topped with airy clusters of pink flowers from midsummer to autumn, with red-backed wing-shaped leaves. It dies back each winter and self-sows from leaf-axil bulbils.

Cold limit: USDA 6-9 (root-hardy, dies back to tubers each winter) · RHS H4 (15-25°C)

Watch for — Tuber rot in winter: Soggy, poorly drained soil over winter rots the dormant tubers; ensure sharp drainage or mulch heavily in marginal zones.

What begonia grandis's hardiness rating actually means

Yes — begonia grandis is genuinely cold hardy. Rated RHS H4 and USDA 6-9 (root-hardy, dies back to tubers each winter), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 6-9 (root-hardy, dies back to tubers each winter) — 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 to −5 °C. Begonia grandis is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for begonia grandis as it gets too cold:

It tolerates winter lows to about −10 to −5 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can begonia grandis go outside or overwinter — and where?

Plant it out within USDA 6-9 (root-hardy, dies back to tubers each winter) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 begonia grandis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Begonia grandis hardiness — frequently asked questions

Is begonia grandis cold hardy?

Yes — begonia grandis is genuinely cold hardy. Rated RHS H4 and USDA 6-9 (root-hardy, dies back to tubers each winter), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Begonia grandis is hardy across USDA 6-9 (root-hardy, dies back to tubers each winter); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature begonia grandis can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Begonia grandis is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is begonia grandis?

Begonia grandis is rated USDA 6-9 (root-hardy, dies back to tubers each winter) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can begonia grandis survive winter outside?

Plant it out within USDA 6-9 (root-hardy, dies back to tubers each winter) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to begonia grandis below its minimum temperature?

It tolerates winter lows to about −10 to −5 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.