Bougainvillea: The October 2023 Houseplant of the Month

Bougainvilleas are one of my favorite plants. How can you resist their colorful, long-lasting blooms? They make quite an impact on our terraces in summer, but here in Canada, it’s unthinkable to leave them outside during winter (they’d freeze to death). With freezing nights just around the corner, it’s time to bring our plants inside, and that includes bougainvilleas. Admittedly, I wouldn’t really call them houseplants, or at least not good houseplants, but it’s certainly possible to keep them alive and more or less healthy between now and next spring.

Origin

In 1766, Count Louis-Antoine de Bougainville embarked on his frigate and set out on a round-the-world voyage, which he recorded in his logbook Voyage autour du monde, published in 1771 as an important work of Enlightenment literature. When the explorer passed through Brazil, naturalist Philibert Commerson and his wife Jeanne Barret discovered a flower that they brought back to Europe for the first time. They named it after the Count.

Fun fact: it may in fact have been Jeanne Barret, a botanist emeritus, who first discovered bougainvillea. However, being a woman, she was not allowed to take part in the expedition and had to disguise herself as a man to become the first woman to circumnavigate the globe. The credit therefore went to her husband.

Name

Depending on classification (botanists still argue over precise lists), there are between eight and sixteen species of bougainvillea, listed in the genus Bougainvillea, belonging to the Nyctaginaceae (Four o’clock) family. Bougainvilleas are probably the only plants in this family to be grown indoors.

History of Cultivation

Although it wasn’t until the 20th century that bougainvillea was cultivated in Europe, then produced and shipped to the various colonies, the plant was already known in South America by various nicknames in Portuguese and Spanish: santa-rita, veranera, três marias, sempre-lustrosa, ceboleiro, roseiro, pataguinha, flor-de-papel, etc.; poetic common names, such as “always bright” or “paper flower”.

Bougainvilleas are used as ornamental plants and ground cover in equatorial to temperate climates (they can survive mild winters such as those found on the Mediterranean coast, where its shrub form abounds, and even withstand light, brief frosts). In continental climates, it is sold as a summer annual, to be discarded at the end of summer to the delight of the sellers, or to overwinter indoors. It can be found in hanging baskets, as a small bush or pruned to resemble a tree, with a single trunk. Finally, it’s also sold as bonsai.

Description

Bougainvilleas are sarmentaceous climbing shrubs, or small trees that produce long, flexible branches in all directions, until they find a support on which to intertwine their branches. Although they can be grown on a stake, they will need to be tied to it, as they do not form climbing organs such as tendrils, voluble stems or root-crampons, unlike many other climbers (which are more efficient at the task).

Bougainvillea stems are woody, becoming grey-barked with age and losing their juvenile flexibility to form a rigid trunk. They can exceed ten meters in length. Their branches are covered with green, elliptical, alternate, slightly crinkled leaves (rather like parchment). Depending on the species and hybrid, the branches are also protected by small or – more often – large thorns (and I can confirm that these thorns are strong enough to hurt you!). In bright light, new growth can temporarily take on a pinkish hue. Depending on temperature and season, their foliage is evergreen or, in regions with dry seasons or cooler winters, deciduous.

A Spectacular Bloom

The shrub would be rather innocuous were it not for its spectacular flowering. With proper care, bougainvillea remains in bloom for several months. The discreet white flowers are surrounded by bracts that are often brightly colored and papery. The bracts can remain on the branch for a relatively long time, and can also be dried to make a permanent bouquet or confetti. Flowering only occurs on new wood, on small, modified stems bearing several bunches.

If the flowers eventually bear fruit, these are small achenes (like those of the dandelion) which are carried by the wind.

Varieties

The majority of bougainvilleas on the market today are the result of complex hybridizations between different species. There are over 300 different cultivars, their origins obscure and difficult to differentiate. The best varieties generally tend to flower all year round under optimal conditions.

The main differences are

• Flowering: the bracts, generally three in number, but more in some double cultivars, are traditionally fuchsia. There are also paler pinks, reds, purples, yellows, oranges and whites. Some are even bicolored.
• Foliage: yes, bougainvilleas come in all sorts of shapes with yellow or cream-edged leaves. Beware: flowering is even less assured for shrubs slightly deficient in chlorophyll.
• Size, habit and speed of growth: there are dwarf, semi-dwarf and reputedly fast-growing cultivars. Depending on needs, a faster-growing shrub may be of interest (for a hedge, to cover a wall, to impress by the pool this summer), just as a slower-growing shrub may have advantages, especially as a houseplant or for a restricted space. For pot cultivation, the main use in Canada, dwarf and semi-dwarf cultivars are particularly attractive.
• Thorns: the best cultivars have more discreet thorns, which leads me to believe that my bougainvillea is definitely not one of the best cultivars.

Grafting Bougainvilleas

Growing Tips

Light

Bougainvillea demands full sun outside, so you can see how unhappy it is indoors! In fact, it’s simple: it never gets enough direct sunlight.

Watering

Watering can be a little tricky. Used outdoors, this is a fairly drought-tolerant plant – in fact, it won’t flower if kept constantly moist. However, during the flowering period, it’s a good idea to keep the substrate slightly damp.

When growing indoors, it needs to be watered fairly frequently (especially large plants), as it loses a lot of water through evapotranspiration. Foliage hangs sadly when the plant is in water deficiency.

When the plant is at rest (especially in winter or with inadequate light), allow the soil to dry out slightly.

Atmospheric Humidity

Atmospheric humidity is preferable at all times, but not a prerequisite.

Potting Soil and Potting

Bougainvilleas love poor or even saline soil. Indoors, normal soil will do just fine.

Fertilizers

Regular fertilization at the recommended dose is beneficial for growing bougainvillea.

Temperature

Bougainvilleas love sun and warmth; they’re not afraid of high temperatures. They can be grown outdoors in zones 9b to 11 (USDA). This means they will survive brief periods of frost, but not if the cold persists for more than a few hours. However, this doesn’t mean they like cooler periods: optimum winter temperatures should remain above 10°C (50?), even when dormant.

Pruning

Being sarmentose by nature, bougainvilleas generally adopt a messy, overflowing growth habit. As with many other plants, pruning the main branch awakens the secondary buds; in this sense, bougainvilleas are rather easy to densify through pruning. As they eventually start to thin out at the bottom (or get too big for the space they need to occupy inside), severe pruning may be recommended. This is best done in spring.

Rest

A second aspect of maintenance is managing the resting period. Although not absolutely necessary, a little nap in the cool is recommended to stimulate beautiful flowering when the good weather returns. However, conditions are not always easy to meet: you want a bright room, but one that stays between 10 and 16°C. Watering should be reduced (but not stopped altogether) for a few months. The combination of temperature and reduced watering tells the plant that it’s time to sleep.

Of course, not everyone has a room that’s both cold and bright. The easiest thing to do is to keep the bougainvillea indoors, even if the temperatures are too hot, the air too dry and the light insufficient. It will continue to grow, but its growth is likely to be stunted by far too little light for its liking. When spring returns, prune as necessary, probably quite severely, and take it outside. Bougainvilleas are much healthier if they spend the summer in the sun! It’s important to manage the spring outing and the autumn return.

In autumn, it’s even simpler: a bougainvillea can be brought in after a bit of a chill, as the colder temperatures and shorter days can help to stimulate its already abundant bloom, so that the show continues through the fall. Here are a few other houseplants to bring in late.

And as an Outdoor Plant?

In terms of summer maintenance, it’s best to place the bougainvillea in the sunniest spot and water it occasionally. Little water is needed for bougainvilleas planted directly in the garden, as they tolerate drought well, but it will probably be necessary for potted plants, which dry out more. A little occasional pruning can encourage new flowering throughout the summer, if a long branch stands out but refuses to bloom.

As mentioned above, bougainvilleas are not plants that remain particularly beautiful indoors: lack of light and humidity (as well as poor watering, because no gardener is perfect) can cause them to lose their foliage quite radically, and new shoots often wither away. Perhaps we should think of them less as strictly indoor plants and more as outdoor plants that can be overwintered without too much difficulty. On this subject, here’s an excellent article by Larry Hodgson: How to Overwinter a Bougainvillea Indoors.

Multiplication

Stem cuttings can be taken to propagate bougainvilleas.

Problems

• Bougainvilleas can be bothered by a number of insects: whiteflies, mealybugs and spider mites. Outdoors, although not particularly problematic, aphids and grasshoppers can attack them. Bougainvilleas even have their own predator, the disclisloprocta stellata caterpillar, a moth nicknamed “bougainvillea looper” because of its appetite for the plant.
• Leaf loss: drastic changes in light, for example when bringing a plant in for the winter, often lead to leaf loss. When bougainvillea runs out of water over a short period of time, leaf drop can also occur. This can happen several days after the plant has been watered, much to the dismay of the gardener who thought he had remedied the situation!

Toxicity

Bougainvillea sap is irritating to humans, and the leaves are toxic to pets. The bracts are edible and used, for example in Mexico, to make tea or decorate dishes (in which case the small white flower is removed). However, remember that most hybrids purchased on the market have not been chosen for their taste or even their edibility, so caution is advised. They are said to have a slightly bitter taste.

Tips for Buying Bougainvillea

For spectacular, long-lasting flowering, choose a bougainvillea in the store that is not yet in full bloom: if you look closely, you can see the tiny bracts covering the new stems, which will emerge over the following weeks. Properly cared for, a bougainvillea can flower almost continuously throughout the summer. Of course, inspect the leaves carefully and choose a plant that is free from disease or pests. Finally, beware of thorns during transport!

Conclusion

How can you resist the breathtaking colors of bougainvillea in bloom? This shrub wows us all summer long, and deserves to be cared for in winter too. Although it’s not the easiest plant to grow indoors, and may lack light, it’s still pretty easy to overwinter, so it can treat us as soon as temperatures allow us to take it outside. Besides, who’s afraid of a few thorns?