Tibouchina heteromalla, commonly known as princess flower and glory bush, isn't easily found at nursery and garden centers, so you can plant this flowering evergreen knowing it will draw the awe of the neighborhood. This specimen's light pruning requirements make it easy to maintain princess flower around a busy schedule. Princess flower must be grown in containers and moved indoors for winter when grown outside U.S. Department of Agriculture plant hardiness zones 10 through 11. Princess flower only grows to 6 feet tall and wide in ground, but grows even slower and requires less pruning when grown in containers.
Pinch out the tips of new growth to encourage newly planted princess bushes to branch out until you achieve the desired width. Check the ends of branches for small, soft leaf sets, and simply pinch them out between your thumb and forefinger. Multiple new branches grow from this point. This is required for shaping the plant for at least the first few months after planting, and also helps to fill out uneven sides of the plant.
Clean and disinfect all pruning tools in a solution of 1 part chlorine bleach to 9 parts water before pruning the princess bush. You'll mostly need bypass pruners for small diameter branches and lopping shears for branches up to 1 1/2 inches in diameter, but a pruning saw might be needed for thicker branches on older specimens.
Cut off spent flowers just above the nearest leaf set to keep the plant looking tidy and extend the blooming period. This might seem like a monumental task when the princess bush is covered with its brilliant, purple flowers, but it's a mindless task that you can complete in only a few minutes each day. This task won't take up any extra time in your schedule if you take your bypass pruners or even a pair of scissors outside with you and deadhead the plant while the kids have afternoon play or the dog goes out to do its business.
Remove all dead, diseased and broken stems throughout the year as soon as you notice them. Cut them back to either the nearest healthy stem or back to the ground if an entire branch is affected. Cut a minimum of 6 inches outside the diseased area of a branch to ensure you remove all disease. Disinfect pruning tools in the diluted bleach solution immediately after cutting through a diseased branch.
Prune poorly placed branches each year in late winter before the plant begins sprouting new growth. This more intensive pruning process also opens up the plant so sunlight can reach the inside, resulting in healthier growth. Cut all rubbing and crossing branches, as well as branches with weak-angled branch crutches, back to the branch union. When selecting between two branches to prune, always keep the strongest branch and those that grow outward rather than toward the center of the plant. Do not remove more than one-third of the total branches in the princess bush each year.
Cut back the tips of excessively long branches in order to maintain a uniform shape throughout the bush. Make an angled cut just above a leaf set or node on the stem. The shrub mostly requires shaping in late winter, but you can trim them back throughout the growing season if they grow too much.