Cold hardiness & minimum temperature

Is Bougainvillea (Bougainvillea glabra)cold hardy? Hardiness zone & min temp

Also called Bougainvillea, Paper flower, Lesser bougainvillea.

More about bougainvillea

About Bougainvillea

Bougainvillea glabra · also called Bougainvillea, Paper flower · flowering

Bougainvillea glabra, or paper flower, is a thorny, sun-loving tropical climber prized for vivid papery bracts surrounding tiny true flowers. Give it full sun, fast-draining soil and lean watering to trigger blooms. Not listed by the ASPCA; the main risk is its large thorns, so verify safety with your vet.

Cold limit: USDA 9b-11 (grow in containers and overwinter indoors in cooler zones) (16-30 C ideal; keep above 10 C)

Watch for — Yellowing leaves and leaf drop: Often overwatering or root rot, but also natural seasonal drop or cold/drought stress. Check drainage and let soil dry; seasonal drop in cool weather is normal.

What bougainvillea's hardiness rating actually means

Bougainvillea 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 9b-11 (grow in containers and overwinter indoors 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 10 °C (sustained cold below this is damaging). Bougainvillea has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Bougainvillea hardiness — frequently asked questions

Is bougainvillea cold hardy?

Bougainvillea 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 can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11 (grow in containers and overwinter indoors in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature bougainvillea can survive?

What hardiness zone is bougainvillea?

Bougainvillea is rated USDA 9b-11 (grow in containers and overwinter indoors in cooler zones) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can bougainvillea 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 bougainvillea 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.