A beautiful large vine native to South America, bougainvillea (Bougainvillea spp.) produces brilliant flower displays when temperatures are warm and rainfall isn't plentiful. Fast and vigorous growing, bougainvillea vines become large and heavy, up to 15 to 30 tall/wide on a trellis, arbor or sturdy fence. Long, needle-like thorns line the branches. Grow bougainvillea outdoors where there is rarely a winter frost, such as in U.S. Department of Agriculture hardiness zones 9 and warmer.
Brilliantly Colored Bracts
The vibrantly colored "flowers" we see heavily festooning the tips of bougainvillea branches are actually papery bracts, or modified leaves. According to Kirsten Albrecht Llamas, author of "Tropical Flowering Plants," the bracts often number three in a cluster, or can be a larger whorled cluster called an involucre. The bracts last for several days and slowly dry and diminish in color, eventually becoming dry, tissue paper-like, and beige as they fall and decompose on the ground.
Closer examination of a bougainvillea in flower reveals small white objects in the middle of all the colorful bracts on branch tips. These are the plants' true flowers. Each tiny white blossom is tubular to urn-shaped and lacks petals.
The small size and tubular shape of the bougainvillea flowers finds hummingbirds being the primary pollinator according to "Tropical Flowering Plants." Other long-tongued butterflies or moths may also frequent the bougainvillea during the flowering display, but only when the true white flowers are present; pollinators may be visually attracted by the showy bracts but quickly realize if no real flowers remain.
Even though a subtropical or tropical landscape plant, bougainvilleas typically do not bear flowers and bracts year-round outdoors. In Mediterranean climates, like that of southern California, they tend to flower most profusely from the late spring to early fall when temperatures are hot and rainfall scarce. Conversely, in monsoonal climates where summers are humid and wet but winters dry, the bougainvillea tends to bloom from fall to early summer until the monsoonal rains return. In southern Florida, for example, winter's sunny, dry and warm weather causes many leaves to drop but a tremendous production of flowers and bracts. Floridata alludes that new flushes of flowers occur if plants are subjected to alternating periods of wet to dry; the dryness tends to result in renewed flower and bract production.
The tiny white flowers of bougainvillea persist only for a couple days, although a cluster of flowers open in succession. The growing bracts are visible before the real flowers open and are at their colorful peak as the flowers open. Once pollinated or aged, the flowers drop off but the bracts persist for weeks.