The bougainvillea is a striking tropical and subtropical plant recognized for its vigorous growth habit and its vibrant, papery bracts, which are often mistaken for the flowers themselves. The true flowers are small and inconspicuous, surrounded by these brightly colored modified leaves. Training this woody, thorny vine involves structural support and precise pruning to manipulate its sprawling nature into a desired, controlled shape. Left unchecked, the bougainvillea can become an unruly, tangled mass of stems due to its rapid growth rate.
Essential Timing and Preparation
The most opportune time for major structural pruning and training is in the late winter or very early spring, just before the plant breaks dormancy and begins its new growth cycle. This timing allows the plant to direct its energy into developing new shoots, which is where the colorful bracts will appear later in the season. Pruning too late risks removing the newly formed buds, significantly reducing the potential for a vibrant bloom display.
It is advisable to wear thick, puncture-resistant gloves and long sleeves when working with this plant due to the sharp thorns found along its stems. Necessary tools include sharp bypass hand pruners for smaller stems and loppers for cutting older, thicker, woody canes. To make the plant more receptive to heavy pruning, gardeners often reduce water and cease high-nitrogen fertilizer applications in the weeks leading up to the main pruning session.
Guiding the Plant onto Support Structures
The bougainvillea is not a self-clinging vine, meaning it does not possess tendrils or sticky pads to attach itself to surfaces. Instead, it uses its sharp, recurved thorns to scramble and hook onto nearby objects for support, which necessitates manual intervention for structured growth. The process begins with selecting the strongest stems to serve as the main leaders that will define the plant’s overall structure on a wall, arbor, or trellis.
These chosen leaders must be manually secured to the support structure. Soft, wide materials like fabric strips, specialized plant ties, or nylon stockings are preferable over thin twine or wire. Hard materials can easily girdle the stem as the bougainvillea grows and the stem thickens, potentially damaging the vascular system.
Branches should be tied loosely enough to allow for future growth and checked periodically to prevent constriction. To encourage a denser display of bracts, it is beneficial to train the stems horizontally. This technique promotes the growth of lateral shoots along the length of the branch, which are more likely to produce the showy, flower-bearing bracts than purely vertical growth.
Specialized Pruning for Desired Shapes
Achieving specific forms requires ongoing and specialized pruning techniques that redirect the plant’s natural vining energy.
Standard (Tree Form)
To train a bougainvillea into a Standard, or tree form, select a single, strong trunk and stake it securely for support. Remove all side shoots and lateral growth from this trunk up to the desired height where the canopy will begin. Once the main trunk reaches the target height, the growing tip is pinched or cut back to encourage branching at the top. The subsequent growth in the crown is then regularly pruned and shaped to create a dense, rounded head, maintaining the clean, single-stem structure below.
Hedge or Bush Form
For a dense Hedge or Bush form, the approach is the opposite of the standard, focusing on continuous, light shaping cuts across the entire plant. Instead of letting canes extend into long, vigorous vines, regularly trim, or “pinch,” the growing tips of the new shoots throughout the growing season. This frequent tip pruning encourages the development of multiple side branches, resulting in a compact, uniform, and dense plant structure.
Espalier
A formal shape, such as an Espalier, involves training the bougainvillea to grow flat against a surface in a specific two-dimensional pattern. This technique requires meticulous selection and tying of lateral branches to a support system, such as a wire grid or lattice. Precise cuts are used to remove any growth that deviates from the intended plane, creating an ornamental pattern by directing the branches to grow horizontally and vertically.