Bougainvilleas are tropical, perennial flowering vines that originated in South America. They can be planted outdoors in gardening zones 8 and warmer, and they can be grown in containers in the cooler regions. Because they need a lot of sun and humidity, bougainvilleas do not bloom well indoors, so taking your container outside for the summer in cooler regions helps bring beautiful flowers to your plant. Bougainvilleas only bloom on new growth, so pruning is especially important if you want to obtain a bushy, flowery display.
Pinch off 1/2 inch of the new growth on the stem right after the flowering cycle has ended. This will force two or three new branches to emerge just under the cut, giving you a fuller plant. Do this until you have the fullness you desire from your plant.
Cut back all branches after flowering has finished, once you have an established plant. Cut from 1/2 inch to 1 inch off from all the branches and it will give you many more flowers for the next flush. Pruning makes the bougainvilleas stronger and fuller, so do not be afraid to cut it back.
Cut back several branches to the main branch at the beginning of summer or if you are planning to move your plant indoors. This helps the roots keep up with the changes the plant will go through, such as hot weather or dryer indoor air.
Cut back any branches at any time to shape the plant or restrict it to a certain area. Bougainvillea does not seem to mind pruning any time of year and, as a matter of fact, it preforms much better when pruned often.
Do not prune the roots. Bougainvilleas have very delicate root systems that will go into shock for weeks when disturbed. Repot carefully and only when the plant is so root-bound that you have trouble keeping it watered.