When you see "Got word?" or "Care to give word?" on the tree, feel free to click on it to enter a word or a phrase. You will see it flying in the wind with all other words and leaves.
The leaves will start falling at a random time. A new tree will be generated at a random time after the leaves have fallen. However, if you want to make the leaves start falling before its time, press the HOME key. If you want to start a new tree before its time, press the END key.