Cold hardiness & minimum temperature

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

Also called great bougainvillea, paper flower.

More about bougainvillea spectabilis

About Bougainvillea spectabilis

Bougainvillea spectabilis · also called great bougainvillea, paper flower · tropical

Great bougainvillea is a thorny, evergreen tropical climber from South America whose vivid magenta, papery bracts surround tiny white true flowers. It blooms hardest in full sun with sparse water — drought stress triggers flowering. Frost-tender, it is grown outdoors in warm climates or under glass in cool ones. Thorns and irritant sap make it best kept away from pets.

Cold limit: USDA 9b-11 outdoors; grown under glass or as a conservatory plant in cooler zones · RHS H2 (tolerant of low temperatures but not surviving below 1-5°C; needs frost-free protection) (10-30°C)

Watch for — Sudden leaf drop: Cold draughts, sharp temperature swings or letting it dry out completely, common when moving plants indoors for winter.

What bougainvillea spectabilis's hardiness rating actually means

Bougainvillea spectabilis 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 9b-11 outdoors; grown under glass or as a conservatory plant 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 1 to 5 °C — tolerates cold but no real frost. Bougainvillea spectabilis shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for bougainvillea spectabilis 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 bougainvillea spectabilis go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b-11 outdoors; grown under glass or as a conservatory plant in cooler zones 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 bougainvillea spectabilis 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 bougainvillea spectabilis

Bougainvillea spectabilis 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.

Bougainvillea spectabilis hardiness — frequently asked questions

Is bougainvillea spectabilis cold hardy?

Bougainvillea spectabilis 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 9b-11 outdoors; grown under glass or as a conservatory plant in cooler zones (and sheltered UK gardens) bougainvillea spectabilis can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature bougainvillea spectabilis can survive?

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

What hardiness zone is bougainvillea spectabilis?

Bougainvillea spectabilis is rated USDA 9b-11 outdoors; grown under glass or as a conservatory plant in cooler zones and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can bougainvillea spectabilis survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b-11 outdoors; grown under glass or as a conservatory plant in cooler zones 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 bougainvillea spectabilis 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.