Cold hardiness & minimum temperature

Is Bougainvillea 'Barbara Karst' (Bougainvillea 'Barbara Karst')cold hardy? Hardiness zone & min temp

Also called Red Bougainvillea, Paper Flower.

More about bougainvillea 'barbara karst'

About Bougainvillea 'Barbara Karst'

Bougainvillea 'Barbara Karst' · also called Red Bougainvillea, Paper Flower · flowering

Bougainvillea 'Barbara Karst' is a vigorous evergreen climber famous for masses of vivid magenta-red bracts almost year-round in warm climates. It thrives on heat, full sun, and lean, fast-draining soil, and actually flowers harder when kept slightly dry. Thorny and fast, it covers walls and fences quickly but resents soggy roots and frost.

Cold limit: USDA 9-11 (frost-tender; container or conservatory in cooler zones) · RHS H1c (18-30°C)

Watch for — Bract and leaf drop: Sudden environmental change, cold draughts, or moving the plant causes shedding; keep conditions stable and above 10°C.

What bougainvillea 'barbara karst''s hardiness rating actually means

Bougainvillea 'Barbara Karst' 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 9-11 (frost-tender; container or conservatory in cooler zones) — 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 5 °C (and never frost). Bougainvillea 'Barbara Karst' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for bougainvillea 'barbara karst' as it gets too cold:

Below about about 5 °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 bougainvillea 'barbara karst' go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 bougainvillea 'barbara karst' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Bougainvillea 'Barbara Karst' hardiness — frequently asked questions

Is bougainvillea 'barbara karst' cold hardy?

Bougainvillea 'Barbara Karst' 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. Bougainvillea 'Barbara Karst' can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (frost-tender; container or conservatory in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature bougainvillea 'barbara karst' can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Bougainvillea 'Barbara Karst' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is bougainvillea 'barbara karst'?

Bougainvillea 'Barbara Karst' is rated USDA 9-11 (frost-tender; container or conservatory in cooler zones) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can bougainvillea 'barbara karst' survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 bougainvillea 'barbara karst' below its minimum temperature?

Below about about 5 °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.