Bougainvillea is a beautiful tropical plant that can be grown outdoors in the hotter areas of the United States. Since most of the U.S. is not tropical enough to support the plant as a perennial, it's often grown as an annual or a potted indoor plant. Bougainvillea are vine-like plants that have sharp thorns that allow them to hook onto stationary objects for climbing. The plants are most well known and popular for their outrageous color: Instead of producing exotic flowers, they produce paper thin bracts in brilliant color that surround very small flowers.
Bougainvilleas love heat and sunshine. In the United States, they thrive as a perennial in USDA Hardiness Zone 9 or higher. They're still grown in areas that go below 30 degrees Fahrenheit--either as annuals or as potted plants that are brought indoors during the winter.
Bougainvillea has very fine roots and needs well drained soil with pH levels of 5.5 to 6.5. Soil that is too heavy or contains too much peat or peatlite retains too much water and will drown and rot the roots of the Bougainvillea plant. Soil-less growing mediums also work well.
As a tropical plant, bougainvillea needs plenty of heat and sunshine. To get the best results with growth and flowering, make sure your bougainvillea gets no less than five hours of direct sunlight each day. Afternoon sunlight is best because that's also when it's warmest.
The plant prefers temperatures to be no less than 65 degrees at nighttime, and daytime temperatures of 75 to 95 degrees F produce the best flowering conditions.
Bougainvillea are drought tolerant plants so how much water you give them will depend upon the growing conditions you have it in. Once the plant is established it generally needs little water, and should be allowed to dry enough that the soil is visually dry before watering again.
Bougainvillea also love humidity, and they flower well when stressed. Common methods of stressing the plant are letting it become root bound in a pot, and allowing it to dry more than usual before giving it a complete watering. This emulates the natural tropical conditions the plant grows wild in, because there is a rainy season followed by a hot dry season.
Bougainvillea are heavy feeding plants that responding well to monthly fertilizing. Adding nitrogen and phosphate is important for flower production, but it's a balancing act because if you add too much you'll end up with a lot of foliage growth but little to no flowering.