Here's Peter Pook in Australia and his living sculpture as a chair.  And here's his website:   http://pooktre.com/photos/

(Click on underlined title to see more) Axel Erlandson created this with six sycamores planted in a ring pattern:  "To create the 'Basket Tree', Erlandson planted six sycamore trees in a circle, topped them all at one foot,