Daniel Gill, Merrill, Thomas A. | 7/28/2005 1:29:17 AM
By Dan Gill
LSU AgCenter Horticulturist
It would be hard to find a more dazzling flowering tropical plant than the bougainvillea.
The bougainvillea (Bougainvillea spectabilis) is a tropical shrubby vine, and its bright magenta, pink, white, gold or purple flowers positively glow.
Actually, though, the colorful parts are modified leaves called bracts. The true flowers, located within the bracts, are small and white.
More of a large sprawling shrub than a true vine, the bougainvillea is wonderfully versatile. They are tough plants, and getting them to thrive and grow is not difficult.
The most common complaint gardeners seem to have is getting them to bloom. It is important to understand that although as a group bougainvilleas bloom from spring to fall, individual plants generally do not bloom constantly. That’s why you may see bougainvilleas blooming in your area even though yours are not in bloom.
Individual plants tend to bloom intermittently on and off throughout the year, with the heaviest production of blooms most common in spring to early summer (if plants are kept healthy over the winter) and in late summer to fall.
It is not unusual for a bougainvillea plant to produce abundant blooms just once or twice a year. Older plants, established plants tend to bloom longer than younger plants, so the more years you have your bougainvillea the more it should bloom for you.
The first step to getting your plant to bloom is to provide as much light as possible. Bougainvilleas will bloom reliably only if they receive six hours or more of direct sunlight each day. Grown in partially shaded locations, these plants will produce healthy, dark green leaves but few or no flowers.
Except in the mildest coastal parts of the state, container culture gives the best results and the most reliable blooming. Use plastic or clay pots or hanging baskets, but make sure they have drainage holes. Any good potting soil or soilless mix is fine as long as it drains well.
Fertilize bougainvilleas in early summer with a slow-release product or fertilize them regularly during the summer with a soluble fertilizer. Should your container-grown bougainvillea begin to grow rampantly, producing large, dark-green leaves, you probably have been too generous with fertilizer, and you should skip fertilizing for four to six weeks.
There are no "magic" fertilizers that will make your bougainvilleas bloom. Most growers use a balanced slow-release or soluble fertilizer with a 1:1:1 ratio, such as 20-20-20 or 14-14-14.
Don’t be too hasty in repotting a bougainvillea that looks like it has outgrown its container. Restricting the root system keeps the plant from growing so rampantly and seems to encourage flowering. If you do eventually decide to move the plant into a larger container, the new container should be only slightly larger than the original pot. Repot into a substantially larger container only if you want to grow a much larger plant, and remember that flowering will be reduced until the new pot is filled with roots.
In addition to proper light, soil, fertilizer and container size, bougainvilleas need adequate moisture for proper growth. Generally, keep your plants evenly moist, allowing them to dry slightly between waterings.
When it comes to pruning, keep in mind that bougainvilleas bloom on new growth. If your plant begins to grow too large or if it sends out a wild, vigorous shoot, feel free to trim it back. This will keep the plant under control and encourage branching without interfering with blooming. You generally can prune occasionally, as needed, but the ideal times to trim back bougainvilleas are whenever they have just finished a bloom cycle and in the late fall or early winter just before they need to be brought into a protected location for the winter.
Despite apparently ideal care, some gardeners still are frustrated by a lack of flowers on their plants. Here is a trick you can use on bougainvilleas growing in containers. Allow the leaves to slightly wilt before you water.
But be careful. The idea is not to let your plant die of thirst. The leaves should not be so wilted that they do not revive when watered. As soon as flower buds appear, generally about four to six weeks after you begin allowing your plant to wilt, resume normal watering.
On the other hand, never let a blooming bougainvillea wilt, or it will drop its bracts and flowers.
There are many different cultivars of bougainvilleas, and they can behave quite differently. Not only do flower colors vary, but also size, growth habit and tendency to bloom differ from one type to another. Some bloom more readily than others, some are bushier and so on. If you grow several types, you will notice these differences.
With careful attention to the cultural guidelines presented here and patience, your bougainvilleas should provide you with the brilliant flowers for which these plants are so well known.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.