Tibouchina is a large genus of flowering plants commonly referred to as glory bushes. The most commonly cultivated species within the genus is "Tibouchina urvilleana," or princess flower, which is a shrubby plant grown for its velvety leaves and summertime display of bright purple flowers. Gardeners in USDA zones 8 to 12 have the best luck growing princess flower since it requires warm temperatures year-round, but it will grow well in greenhouses in cooler climates. Some gardeners may choose to reproduce particularly attractive Tibouchina specimens, and there is no better way than through softwood cutting propagation.
Fill a 4-inch-deep seedling flat with coarse sand. Saturate the sand with water using a garden hose with a misting nozzle to settle it and moisten it throughout its entire depth.
Create planting furrows across the sand using a putty knife or another narrow implement. Space the furrows 2 inches apart.
Sterilize the blade of a utility knife or other very sharp cutting tool before taking cuttings from the Tibouchina plant. Dip the blade in undiluted hydrogen peroxide for 30 seconds, then allow it to air dry.
Select several cuttings from the stem tips of a mature and healthy Tibouchina. Choose cuttings with light green immature foliage at the tips and straight, pliable stems.
Measure 4 inches from the tip of the stem. Sever the Tibouchina stem using the sterilized utility knife. Cut the stem straight across with no angling. Remove all foliage from the bottom 2 inches of the cutting either by pinching it away or slicing it free with the utility knife.
Wound the cut end of the Tibouchina cutting with the utility knife. Scrape away a 1/2-inch-long section from the outside of the stem to expose the vascular inner flesh.
Dip the wounded end of the Tibouchina cutting in 0.1 percent IBA rooting hormone until it is fully coated. Make sure the entire lower 2 inches of the cutting are coated in the hormone.
Insert the cuttings into the premade furrows in the seedling flat of coarse sand. Space them 1 inch apart in the furrows. Press the sand closed around them to expel any trapped air.
Place the flat on a garden bench in partial shade for the first 10 days. Mist the cuttings with water as often as possible to keep the sand moist to a depth of 2 inches and the aerial portions of the plant from drying out. Move the seedling flat to a slightly sunnier location after 10 days, but make sure it has some protection from midday sun to keep the foliage from scorching.
Transplant the Tibuchina plants after one month, either into separate pots filled with standard potting soil or directly into the garden in a draining bed with full sun.