Plant Answers

Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, June 30, 2007

“Growing Bouganvillea”

Bouganvillea is the premiere patio plant for full sun in San Antonio. It is very colorful, relatively easy to grow and very heat tolerant. Grow bouganvillea in full sun at the hottest location in your landscape.

Bouganvillea is one of the few plants that is actually easier to grow in a container than in the ground. It is hard to believe, but our soil has too many nutrients for good bougainvillea. I should rephrase that, the plants grow great, but they do not bloom. You may have experienced the phenomenon when your bougainvillea entered the soil through the drain hole or through a crack in the pot. The leaves grow to three or four inches and the vine adds six-eight inches of growth each day, but without the benefit of the colorful bracts we call flowers.

The keys to good bougainvillea bloom are a contained root system, a soil that dries between waterings, reasonable fertilization, some pruning and full sun. It is true, bougainvilleas bloom best when the roots are restricted. Plants in containers only begin their bloom period after the roots have filled the container. Repotting bouganvillea is less of an issue than it is for other plants, they will perform well for years without repotting.

Bouganvillea seem to bloom best when the top is about 1.5 times as large as the roots. A twelve inch pot supports a top of about 18 inches around and high. Prune off the tips of the shoots to maintain that size. The tip pruning technique also results in side branching so there are more blooms. The blooms occur at the end of the branches. Tip pruning means pulling of one inch or less of branch every two weeks.

Irrigate bougainvillea only when the soil has dried to two inches. Many gardeners wait until the plant wilts before they water. Water enough to have moisture emerge from the drain hole. Fertilize bougainvillea with a soluble fertilizer such as Miracle Gro, Peters, or Rapid Gro every other time you water. The other option is to use granular hibiscus food. It seems to work very well and is easier to use than mixing up the soluble fertilizer.

Bouganvillea are not usually bothered by insects or diseases. Control the occasional caterpillar attack with Bt or Spinosad. The plants are cyclical bloomers. Expect six week of color followed by an equal period of green. They are very sensitive to cold. Blooming stops when temperatures fall into the low 50’s and freeze damage can occur in the high 30’s. The good new is that bougainvillea are easy to store for the winter. They do not need light so you can prune them back and stack them up in the garage or spare room from November until April.

There are a number of bougainvillea selections. The most popular selection is Barbara Karst. It has a red (dark pink) bloom and is a heavy bloomer. The lavenders, darker reds, off whites and yellows have appeal, but do not bloom as heavy. There are also doubles and variegated selections. The doubles are very attractive, but hold on to spent blooms. They look best if they are groomed every few days. The single bloomers like Barbara Karst drop spent flowers without requiring removing them.