Climber: Frost Hardy Bougainvillea spectro-glabra can grow to a very large plant, 6m high by 3m wide; although for this it needs to be exceptionally happy, most specimens remain about 3m tall. Oval slightly pointed green leaves are borne on a multi stemmed plant.
Flowers: small yellow flowers are held in showy purple bracts, in clusters. July – first frost.
Drought tolerance: 2- see our post on drought tolerant plants for an explanation.
Full sun only.
Comment on Frost Hardy Bougainvillea
I was counting the number of Bougainvilleas I have planted over the last 7 years this morning; 15 in total. On the whole my frost hardy Bougainvillea project has been an abject failure for only 2 are growing successfully. If that kind of failure rate applied to my whole garden…just think.
Nevertheless, at least the reader can learn from my experiences which do show that it is possible to cultivate Bougainvillea in a climate where we have brief frosts to -5 C
The typical Bougainvillea spectabilis (purple flowers) can only take a very light frost before the plants dies above the ground. The roots will survive if the frost is not for long and if the plant is heavily protected it can overwinter and sprout from the roots. However the plant has been so damaged it will take ages to recover and it will die next time it gets stressed
All the coloured Bougainvilleas (white, yellow, orange red) are semi-tropical and tropical and will not survive any frost. Even as a garden annual they are a waste if time; don’t be tempted.
The only Bougainvillea for this climate is the species called Bougainvillea spectro-glabra. An established plant can take -8C or so, younger plants perhaps only -5C – make sure that you protect them in their first winter. It can occasionally be seen in garden centres usually misnamed but with a description of it being the type of Bougainvillea that grows along the French Mediterranean coast. Alternatively you will see large plants of it growing and flowering in houses all over the coastal part of the Languedoc. Take cuttings in mid spring, strike rate is lowish, so take plenty.
This Bougainvillea has larger leaves and larger flower bracts then B. spectabilis. this is another way to recognise it.
As for growing it, it is a fussy plant:
- it needs full sun, against a wall for maximum warmth, either south facing or south west facing. It hates wind
- it hates a clay or enriched soil, it will go sulky and stunted - don’t feed it either.
- it loves a gravel soil with very little organic matter. My 2 grow in pure gravel with hard core underneath
- it is highly susceptible to iron deficiency, chlorosis, if it takes hold it is very hard to kick the plant out of it. Water with iron chelates twice a year as a preventative.
- it is sulky when transplanted – it will be at least 2-3 years before there are any flowers and probably 4 before it starts to get its feet down.
Despite this I adore this plant; what else produces such amazing colour in the full heat of the summer? Campsis radicans is another excellent summer flowerer.