Bougainvillea bonsai require the same general care instructions as the bougainvillea in its native vine form. Since the plant is of tropical, South American origin, it thrives in climates where the heat level is high, with temperatures at least at 60° Fahrenheit (15° Celsius) at night and reaching over 100° Fahrenheit (38° Celsius) in the daytime. Caring for bougainvillea bonsai typically wouldn't require much water, as the native vine itself is adapted to light rainfall patterns, but the weakness of the evergreen plant is its root system. Since roots on a bougainvillea tend to be thin and delicate, they can be even more fragile and dry out quickly for a bougainvillea bonsai that is potted in a small, confined space of a container. When they are placed indoors, proper care involves ensuring that they get at least five hours of direct sunlight each day, as the plant naturally grows near the equator where full sun is the norm.
Plant hardiness zones for the bougainvillea bonsai if it is kept outdoors range from level nine and up, with nine representing the southern border of the US, including Texas, Florida, and the coast of California around 20 degrees to 30 degrees latitude. In Europe, this equates to most of Greece and Italy, coastal regions of the UK, and the southern half of Spain, as well as farther south. If a bougainvillea bonsai is brought indoors during colder periods and especially during winter months, however, it can thrive in colder climates. Where the temperature drops below what is normal for the plant, it needs to be wintered over in a cool area with limited light such as a basement, like most bonsai require in order to survive year after year.
As a bonsai plant, the bougainvillea will flower most prominently as winter approaches and in the early spring. In climates where the bougainvillea bonsai must go dormant and die back in the winter, this flowering process may be interrupted. Flowering can be encouraged in this case by fertilizing it with a high-nitrogen fertilizer in the spring and limiting its exposure to daylight to no more than nine hours per day. As a common rule, bougainvillea require fertilizer that is concentrated with micronutrients like iron which strengthens the roots, but normal nitrogen concentrations should be low.
Many people wonder how to grow bougainvillea bonsai, as pruning and cutting back on bonsai in general can be traumatic for the plants and can, in some cases, kill them. The bougainvillea handles pruning well, however, and, as a branch experiences blooms that have faded, it should be cut back to encourage others to grow. Each branch cutting needs to be sealed properly to prevent rot from setting in and, if it does appear, then the entire branch should be removed.
There are several other considerations to keep in mind when caring for this species. Repotting of bougainvillea bonsai to encourage further growth is best done in spring and the roots should not be trimmed in the process if possible because the plant enjoys being root bound. Many types of pests can also plague the plant, chief among them being its susceptibility to fungus that grows in humid conditions and can attack the roots and kill the plant. The pH of the soil should also be slightly acidic to slightly basic at a level of 6.5 to 7.5, with regular fertilization regimes which can include phosphate to encourage blooming.
The bougainvillea was first discovered by the French botanist Philibert Commercon in 1768. It has since become widespread in regions like the Philippines, and the US state of Hawaii. It can bloom in colors in the popular red-orange-yellow spectrum as well as violet and white.