The tree is about 1m high and was very leafy when I first planted it. The soil is generally very clayish. I have been watering the tree 1-2 times per week. More recently, I have started watering it every 2-3 days. I am not sure why the leaves are turning brown. I also noticed that after a recent day of rain, the few remaining leaves turned more brown and curled up. I have since cut off most of the leaves.
21 February 2019 10:32 PM
Tibouchinas enjoy a well drained acidic type soil. It could be that the pH of your soil is too high and this can cause leaf burn at the edges of the leaf. It might be a good idea to take a sample of your soil to your local nursery to test the pH. You can acidify the soil by adding a Yates product called Acitone. This product will correct and maintain the acidity of the soil. Tibouchinas enjoy an even moist soil and don't like to dry out, so regular watering is essential. If the soil is heavy clay, you might consider improving the drainage by applying Liquid Gypsum which improve the drainage without affecting soil acidity.