Most of the basils are theoretically perennial here, in that they love the winter weather. But I find they get leggy and woody, and the plants are pretty ugly by the second summer. Tree basil, as you said, Jim.
Since it starts so easily from cuttings, when the plants get too big and woody, I just start a bunch of cuttings and ditch the big plants. I have basil going in the garden all the time.
