Bougainvillea Care: How to Get Masses of Colour

Few plants can bury themselves in colour the way a bougainvillea can. On a Mediterranean wall it flowers for months; in a pot on a sunny terrace it can do almost the same — provided you understand one counter-intuitive rule: bougainvillea blooms hardest when life is slightly tough. Too much water, too much fertiliser, or too little sun, and you get a healthy green climber with no colour at all. Here's how to get the balance right.

Bracts, not flowers

The papery magenta, orange, white or purple 'petals' are not petals at all. They are bracts — modified leaves that surround the true flowers, which are the tiny cream tubes at the centre of each cluster. Because bracts are leaves, they hold their colour for weeks, far longer than a normal petal would. That's the secret behind bougainvillea's marathon flowering window: in good conditions a plant produces flushes of bracts from spring right through to autumn.

Light: the non-negotiable

Bougainvillea is a full-sun plant, full stop. It needs at least six hours of direct sun a day to set buds; with less, it survives but sulks. Give it the hottest, brightest spot you have — a south-facing wall, an unshaded balcony, the sunniest corner of the greenhouse. Indoors, only a large south-facing window or a conservatory will do. If your plant is leafy but colourless, insufficient light is the first suspect.

Watering: lean and deep

Water thoroughly, then let the top few centimetres of soil dry out before you water again. In high summer a potted bougainvillea may need water every day or two; in cooler spells, far less. What it cannot stand is constantly wet feet — soggy compost rots the fine roots and triggers leaf drop. Mild drought stress, on the other hand, actually encourages a flush of bracts, which is why plants in lean, free-draining soil often outbloom pampered ones.

Soil, pots and repotting

Use a free-draining, loam-based compost with some added grit or perlite, in a pot with generous drainage holes. Bougainvillea flowers better slightly root-bound, so resist the urge to upsize every year — repot only when roots circle the pot densely, and then only one size up. The roots are famously brittle: handle the root ball gently and never bare-root the plant.

Feeding for colour

From spring to late summer, feed every one to two weeks. Early in the season a balanced feed supports growth; once buds and bracts start to show, switch to a high-potassium fertiliser (a tomato feed works well) to keep the colour coming. Avoid high-nitrogen feeds in summer — they push soft green shoots at the expense of bracts. Stop feeding entirely in autumn and winter.

Pruning and training

Prune in late winter or early spring, just before new growth begins. Bougainvillea flowers on new wood, so cutting back hard at this point costs you nothing and gives you a dense, floriferous framework. After a flush fades in summer, you can shorten long, whippy shoots by up to half to encourage a second flush. As a vigorous scrambler, it needs a trellis, wires or a frame to climb; tie in new growth while it is young and flexible.

Overwintering

Bougainvillea is frost-tender. Below about 10°C it starts dropping leaves; a real frost can kill it. In cold-winter climates, bring pots into a bright, cool, frost-free place — an unheated conservatory, porch or greenhouse at 5–12°C is ideal. Water only occasionally, just enough to stop the root ball drying out completely. Losing some or even most leaves in winter is normal, especially in cooler storage; the plant regrows in spring.

Why is my bougainvillea not flowering?

• Not enough sun — fewer than six hours of direct light is the most common cause.
• Too much water — constantly moist compost keeps the plant in leafy growth mode.
• Too much nitrogen — switch to a high-potassium feed.
• Pot too big — a recently over-potted plant puts energy into roots and leaves first.
• Pruned at the wrong time — cutting in late spring or summer removes the new wood that carries the show.

Common problems and pests

• Sudden leaf drop: usually cold draughts, a cold night below 10°C, or waterlogged compost.
• Yellowing leaves: overwatering first, then nutrient deficiency in tired compost.
• Aphids, mealybugs and whitefly: check shoot tips and leaf undersides; treat early with insecticidal soap.
• Spider mites: fine speckling and webbing in hot, dry, indoor conditions — raise humidity and rinse the foliage.

Tip: if a mature, sun-baked bougainvillea still refuses to colour up, try withholding water until the leaves just begin to wilt, then water deeply. Repeated once or twice, this controlled drought is an old grower's trick for triggering bud set.

Warning: bougainvillea stems carry serious thorns, and the sap can irritate skin. Wear proper gloves and long sleeves when pruning — a scratch from a thorn is often more irritating than a rose's.

Not sure whether that unlabelled magenta climber at the garden centre is a bougainvillea — or which of the 300-odd cultivated varieties you've inherited? Snap a photo in PlantMe: the app recognises over 35,000 plant classes with 93% top-3 accuracy, and its care reminders will nudge you when it's time to feed, prune or bring the pot indoors.