Bougainvillea (Bougainvillea spectabilis), also known as paper flower, belongs to the family Nyctaginaceae. A fast-growing evergreen vine with thorny branches, bougainvillea has clusters of showy, large flowers that are reddish-purple, pink, red, orange or yellow. Heart-shaped, rich green leaves measure 3 to 5 inches long and drop for a period in winter. Flowers are small, yellow-white waxy tubes, surrounded by three 1 to 2 inches long papery bracts that give the plant its colorful display.
Bougainvilleas are tropical plants; therefore, protection from frost is necessary, especially while still very young. Maintain temperatures that are quite high, which is a minimum of 65 degrees F at night and 75 to 95 degrees F during the day, to ensure their survival. Cool temperatures can delay growth, especially when the soil is also cool. Bougainvilleas are hardy to U.S. Department of Agriculture Plant Hardiness Zones 9 to 11.
As a tropical plant, bougainvillea requires full sun--at least six hours of direct sunlight per day. In some cases, the plant can grow in partial shade, but the blooms will not be as plentiful. Bougainvillea does not bloom indoors. Placing a potted plant out on a porch where at least four hours of sunlight may be enough to help bougainvillea bloom sparsely.
Bougainvillea will thrive in well-drained and fertile soil. Avoid soil mixes with high peat levels and water-retention additives because they may stay too wet and encourage root rot. One of the best choices is a soil-less medium, which is free of any insect pests, diseases and weeds. Avoid peat or peatlite mixes alone because they tend to become compacted and hard to wet, which can cause root ball to pull away from the side of the pot. A very dry soil mixture is difficult to handle and may damage tender roots before watering. Soil pH should be 5.5 to 6.5.
Although bougainvilleas require a soil that drains well, you should not let plants to totally dry out between watering. According to the Bougainvillea Growers International, soil should be "visually dry," but not bone dry, as bracts and flowers will begin to drop at this point. "Wilting is the best indicator that water is needed," said BGI in "The Five Rules of Bougainvillea Care." Do not allow plants to stay in standing water.
A healthy bougainvillea in a container will drink a lot of water during the warm times of the year. In cooler periods or when you bring your bougainvillea indoors for the winter, the water requirement will be much less. The amount of water a bougainvillea needs depend on soil type, root system, size of plant, and air temperature. Remember during the summer heat plants will use up water quickly, so inspect for signs of wilting often and water often.
Bougainvilleas are heavy feeders; they require regular fertilizers once a month. Use fertilizers with high phosphorus with micronutrients, as well as additional iron and magnesium. Nitrogen and phosphate are critical to flowering, but avoid over-fertilizing with these two elements so as not to inhibit blooms. Bougainvilleas grow best with small amounts of nutrients constantly available. Slow or timed release fertilizers work well, provided you follow the labels. Avoid adding fertilizers to dry soil.