There are several types of Tibouchina with the standard type and dwarf Tibouchina being the most commonly seen. The standard type (Tibouchina urvilleana) can reach 7 feet or more in size but since it is so cold tender it is often grown in containers so it can be moved in for winter. Thus it doesn't reach nearly as large when container grown. You don't need to do any particular type of pruning other than trimming as needed to maintain an acceptable shape and/or size. The root system is spreading like most shrubs when grown in the ground. If you choose to grow it in a container use as large of a container as is practical so the plant can get as large as it can and thus have more branches for more blooming. 'Athens Blue' is a superior variety of the standard type of Tibouchina. Dwarf Tibouchina is more of a groundcover or hanging basket/container plant. In addition to these two types there are several other Tibouchinas that may be found in the nursery trade.
In zone 9 both types of Tibouchina will freeze to the ground in winter. A morning sun and afternoon shade location is ideal. Fertilize with either a slow release product applied in spring for summer long feeding or with a soluble plant food applied every 2-4 weeks according to label instructions. That plant is not prone to any particular disease or insect problems.
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