When you picture a bougainvillea, often a dense shrub covered with colorful blossoms comes to mind. While this may be the typical bougainvillea that many gardeners grow, you can also train a bougainvillea into a tree shape with careful and attentive pruning. Start training a bougainvillea into a tree shape while the plant is young and then continue to keep the plant growing in a tree shape by removing new shoots.
Choose the strongest central shoot that will become the trunk of the bougainvillea tree. Allow this shoot to grow freely.
Remove all other main shoots growing up out of the crown by cutting them off just above the soil with the pruning shears.
Pound the wooden stake into the soil approximately 6 inches away from the central shoot you are training as the trunk of the bougainvillea tree. Use the hammer to pound the stake approximately 6 inches into the soil.
Tie the central shoot to the stake with the twine, taking care not to injure the shoot by tying it too tightly. This will help train the central shoot to grow as a straight tree trunk.
Remove new shoots as they grow off the crown and the central trunk by trimming them off with the pruning shears. Stay vigilant to remove these shoots immediately as they appear.
Allow the central shoot to grow as a trunk until the bougainvillea tree is as tall as you desire. When the tree reaches your desired height, use the pruning shears to trim the top 2 to 3 inches of the growing tip from the central shoot. This will encourage lateral growth and the bougainvillea tree will fill out and become bushy.
Watch the lateral shoots that branch off from the top of the bougainvillea tree in response to the trimming you performed in step six. Continue to remove the top 2 inches of growth in these shoots to keep them bushing laterally instead of growing up.