You can grow spectacular bougainvilleas

Richard Bogren, Gill, Daniel J.  |  7/28/2009 12:45:35 AM

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For Release On Or After 08/22/09

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 whose bright magenta, pink, white, gold or purple flowers positively glow. Actually, 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.

Bougainvilleas 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 other bougainvilleas blooming in your area even when 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’s not unusual for a bougainvillea plant to produce abundant blooms just once or twice a year. Older, 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 or more hours 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 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.

No “magic” fertilizers 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 can generally 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 are still frustrated by a lack of flowers on their plants. Here is a trick you can use on bougainvilleas growing in containers that is usually effective: Allow the leaves to wilt slightly before you water. Be careful. The idea is not to let you plant die of thirst. The leaves should not be so wilted that they do not revive when watered. As soon as flowers buds appear, generally about four to six weeks after you begin allowing your plant to wilt, resume normal watering. Never let a blooming bougainvillea wilt, or it will drop its bracts and flowers.

Bougainvilleas come in many different varieties, and they can behave quite differently. Not only do flower colors vary, but 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 patience careful attention to the guidelines presented here, your bougainvilleas should provide you with the brilliant flowers for which these plants are so well-known.

Rick Bogren

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