How to grow bougainvillea

A familiar sight in the Mediterranean, where it clads villas in falls of vivid cerise purple and fuchsia pink, bougainvillea is pure joy. In the UK, it can be grown on a smaller scale under cover and wheeled out to grace the terrace during the warm summer months.

In its native South America, this liana (climbing shrub) pulls itself up trees and other structures using the thorns on its stems as crampons. The colourful papery 'flowers' it is covered in during summer are in fact bracts; the true tiny flowers are nestled amongst the bracts and are often visible as white dots. At their best, bougainvilleas bulge in masses of these weird and wonderful confetti bracts, like plants made of tissue paper.

In warm climes, the more vigorous vines are capable of scaling 10 metres or more and remain evergreen. Whereas, here in the UK, they won't be as rampant and usually lose some or all of their leaves in winter.

There are 17 species, with the most cultivated being Bougainvillea glabra and B. spectabilis, which both hail from Brazil; the hybrid B. x buttiana is also widely grown. All three have fabulously gaudy bracts in shades of neon magenta, but the 300 or so garden varieties include white, yellow, orange, lilac, red, and two-tone forms.

The more compact cultivars can be grown as houseplants, but the bigger bougainvilleas will coat the sunny wall of a conservatory in a curtain of colour. In good conditions, they should perform throughout summer and into autumn, cheering you with paper clouds of electric hot pink.

Which bougainvillea to grow

• 'Alexandra' is a good variety with pink-purple bracts and reaches a decent size. Red-magenta 'Barbara Karst' is also excellent and a vigorous grower.
• If you are racy enough to try one of the unusual colours, 'California Gold' is rich yellow and 'Tomato Red' is scarlet.
• To enjoy bougainvillea as a houseplant, opt for a compact form, such as 'Helen Johnson' or 'Vera Deep Purple'. Bougainvilleas can also be bought and trained as beautiful bonsai.

How to plant a bougainvillea

In a greenhouse or conservatory, bougainvillea can be planted in beds, unless you want to enjoy it outside in summer, in which case a pot is better. The root run is deep, but some containment will enhance flowering, so beds or pots don't need to be huge. You can add a bit of soil to greenhouse beds, if it isn't very alkaline (bougainvilleas like slightly acid soil), but compost should make up half the mix or more to prevent waterlogging. Ensure the container has more than one drainage hole (bougainvillea hates its feet soggy), use a loam-based compost, sit on a plant caddy to make it easy to wheel outdoors, and provide support, such as an obelisk.

How to grow bougainvillea

In the Mediterranean, bougainvilleas are a doddle to grow, but, here, they are divas that demand some TLC.

• Under cover: in the UK, bougainvilleas must be grown under cover for most of the year, unless you have a sheltered garden in south Cornwall. Compact varieties can be kept as houseplants. A heated greenhouse or a conservatory is ideal for the large forms; during the warm summer months, they can be placed outside in full sun.
• Temperature: in winter, keep the plant above 7°C. 10°C is a better minimum temperature, if possible.
• Light: bougainvillaea demands a glasshouse with lots of light or, when outdoors, a site in sheltered south or west-facing sun. As a houseplant, sit it on a bright, light windowsill. If keeping your bougainvillea indoors in a sun-baked south-facing conservatory or greenhouse during very hot summer weather, you may need to provide some shading and/or good ventilation.
• Moisture: the main mistake people make with bougainvillea is overwatering. It is drought tolerant and prefers a slightly parched growing medium to excess water. The compost can be kept moist (but never waterlogged) during the growing season; water when the top layer feels dry. Watering with rainwater is preferable, if you collect it. Keep the plant almost dry in winter. Bougainvilleas prefer low to average humidity.
• Food: feed during the growing season. In early spring, give a balanced liquid feed every fortnight. In late spring, swap it for a high-potash feed. Then, during summer, switch back to the balanced feed. Replace the top layer of compost in spring.
• Support: provide a climbing structure or frame, such as canes or an obelisk for a small plant and wall wires or strong trellis for larger plants.
• Pruning: tidy big plants with a trim in autumn, if need be, but do the main prune in February or March. Bougainvilleas flower on new wood, so the yearly haircut is important. The pruning routine is not dissimilar to that inflicted upon climbing roses: to begin with, focus on establishing a fan-shaped framework of a few strong stems – cut these back by three-quarters or more and discard the weaker stems. Then, over the next few years, prune your main stems back by two-thirds to three-quarters and trim side shoots to one or two buds. Eventually, mature plants need only have their main stems cut by a quarter or less (in a confined space or container, obviously remove more); take out dead, diseased, and congested growth; and trim side shoots to two buds or leaves.
• Repotting: a slight root restriction encourages flowering. If necessary, repot in spring, taking care not to damage the fragile roots.

Safety

• Pets: bougainvilleas are toxic to dogs and cats.
• Thorns: the woody stems are thorny, so wear gloves when handling bougainvillea.

Outside Interests: Sign up to our weekly garden newsletter from Clare Foster