Cold hardiness & minimum temperature

Is Begonia 'Sachsen' (Begonia rex-cultorum 'Sachsen')cold hardy? Hardiness zone & min temp

Also called sachsen rex begonia.

More about begonia 'sachsen'

About Begonia 'Sachsen'

Begonia rex-cultorum 'Sachsen' · also called sachsen rex begonia · houseplant

A rex begonia grown purely for its dramatic foliage, with large spiralled leaves zoned in silver, deep green and rosy-pink to purple. Flowers are insignificant and best removed. It wants bright indirect light, high humidity and a careful watering routine; rex begonias are thirsty for moisture yet quick to rot if overwatered.

Cold limit: USDA 10-11 (indoor in most US and UK homes) · RHS H1b (16-24°C)

Watch for — Rhizome and crown rot: From overwatering, burying the rhizome or cold wet soil in winter. Plant the rhizome on the surface and cut watering back in winter.

What begonia 'sachsen''s hardiness rating actually means

Begonia 'Sachsen' 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 10-11 (indoor in most US and UK homes) — 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). Begonia 'Sachsen' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for begonia 'sachsen' 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 begonia 'sachsen' 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 begonia 'sachsen' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Begonia 'Sachsen' hardiness — frequently asked questions

Is begonia 'sachsen' cold hardy?

Begonia 'Sachsen' 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. Begonia 'Sachsen' can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor in most US and UK homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature begonia 'sachsen' can survive?

What hardiness zone is begonia 'sachsen'?

Begonia 'Sachsen' is rated USDA 10-11 (indoor in most US and UK homes) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can begonia 'sachsen' 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 begonia 'sachsen' 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.