Answer: Tibouchina requires some pruning to keep it from becoming weedy and top heavy. It flowers on new wood so pinching and pruning will encourage the growth of new flowering wood. Any stems that have no leaves should be cut back; either to ground level or at least by a third. If you cut them back to their point of origin, the plant will develop healthy new stems; if you reduce their size by a third, the plant should develop new leaves at the base of the stem. The result really depends upon whether or not the stem is still alive. You can check for live tissue by scraping the bark on the stem; green tissue directly beneath the bark indicates live material. These stems can be reduced in length. Brown tissue beneath the bark indicates dead material and these stems can be cut off at their point of origin. Pruning now will encourage new growth; tip pinching throughout the summer months will result in a dense, compact growth habit. You can prune to different lengths. How often your plant will bloom will depend upon the growing conditions but it should produce a new flush of blooms every 4-6 weeks. Hope this explains the pruning process!
Q&A Library Searching Tips