Bougainvillea's colorful papery flower bracts hide small white flowers. The plant can sprawl, trellis or creep along a garden bed, taking any shape the gardener will train it to. Trimming a bougainvillea combines two procedures: pinching and pruning. Pinching promotes flowering, while pruning shapes the plant and promotes the growth of new branches. Pinching or pruning can be completed at any time, so long as the plant isn't in an active flowering cycle.
Pinch off the new tips of your bougainvillea to promote new growth. Using your fingers or anvil pruners, grasp the tip of a new shoot between your fingers and pluck it off. New side branches will grow; with time your bougainvillea will appear bushier. Bougainvillea Growers International advises pinching your plant after each flowering cycle or roughly every four to six weeks.
Identify dead wood on your bougainvillea, which will have discolored or no foliage. Since this won't bear new growth, it should be removed.
Cut off dead growth at its base using anvil pruners.
Remove branches that crisscross other branches, since their rubbing will cause damage. Cut off the crossed branch at its base.
Prune back lateral shoots, leaving only two to three buds per lateral shoot.
Remove weak shoots from crowded areas of your plant by cutting them off at the base. The University of Hawaii notes that you can remove up to 1/3 of the shoots at a time.
Trim back long branches by up to 1/3 to reduce the size of your bougainvillea and promote new growth.