Bougainvillea splashes brilliant colors onto white adobe-wall "canvases" in many of the world’s most arid environments. Those hot hues actually come from leaf bracts, as the vine's true flowers are paltry in comparison. A tough and thorny plant native to Brazil, bougainvillea (Bougainvillea spp.) is seldom bothered by pests and disease, and can clamber to 30 feet when planted in the ground. Perennial only in U.S. Department of Agriculture plant hardiness zones 9 to 11, it scorns indulgent treatment, and will usually only bloom if kept thirsty. In colder zones, it can be grown in a large container.
Plant bougainvillea in spring, in USDA zones 9 to 11, near a warm wall or arbor on which it can climb. Choose a site protected from strong wind gusts, in full sun with sandy and well-drained soil. Ease the plant out of its pot and into the ground before its roots have reached the edges of its container, as bougainvillea resents root disturbance.
Scatter 1/2 pound of 1-3-2 granular organic fertilizer over the surface of the soil around the plant, along with the same amount of bone meal. Dig the amendments into the soil, and water it deeply at least twice in the first week. Mulch the bougainvillea with composted manure, and continue watering it frequently during the spring, while it becomes accustomed to its new position.
Reduce watering to a deep drenching only about once every two weeks during the summer and fall, as the plant is more inclined to bloom when slightly stressed. Overwatering will produce lots of new leaves but few flowers. Bougainvillea shouldn’t require irrigation in the winter or spring, unless the weather is very dry.
Expect the plant to perform off and on year-round, as long as temperatures remain above 60 degrees Fahrenheit. Water it with compost tea once after each flush of flowers is finished, to encourage it to bloom again.
Prune the bougainvillea in late winter or early spring, removing all dead growth and cutting long shoots back to about 18 inches. Apply the same amount of fertilizer and bone meal as in the previous spring, along with some fresh composted manure.
Raising Potted Bougainvillea
Grow a container bougainvillea in a clay pot at least 12 inches wide or in a hanging basket of the same size. Plant it in a fast-draining potting mix, such as one intended for cacti. Move the pot outdoors during the summer, and place it atop bricks or flat rocks -- to prevent the bougainvillea from sending roots through the drainage holes into the ground.
Water the pot every other day or so to keep its soil barely moist. Continue to fertilize the bougainvillea, as long as temperatures remain above 60 degrees F, with a water-soluble plant food at only half-strength. Use about 1/2 tablespoon of crystals per gallon of water once every two weeks, reducing that amount to 1/4 teaspoon per gallon when the plant is moved back indoors in the autumn.
Stop fertilizing the bougainvillea and allow it to go dormant during the winter, if you don’t have a sunny window in which to keep it during that period. Place it in a bright, chilly spot where the temperatures remain above freezing, water it only enough to keep its soil barely damp and expect it to drop its leaves. Add fresh potting soil in the spring and return the plant to warm conditions and regular feeding, but keep it slightly root-bound at all times.