NC artist Patrick Dougherty has just completed this 25 foot tall sculpture "Summer Palace" at the Morris Arboretum of the University of Pennsylvania. According to the press release by the arboretum, the tractor-trailer size loads of sticks and saplings to build the sculpture were gathered locally just prior to the 3 week installation process. The thousands of saplings (a mix of willow, dogwood, cherry, ash and maple) had to be fresh and supple because Dougherty's sculptures are designed and executed without the use of nails or other supportive hardware.
I was not familiar with this artist so I followed links to his some of his other work (Stickworks). The imagination, scale, and sense of movement in his sculptures is awesome! According to his own blog, the sapling sculptures have a life of 2 years before they are destroyed by agreement. During the last two decades, he has built over 150 works throughout the United States, Europe and Asia using the primitive techniques of building with tree saplings.
Sculpture in the Parklands (in Ireland) has a great series of photos showing the process of building one of his sculptures and I highly encourage you to check them out! I also particularly liked the pieces lighted at night at the Museum of Outdoor Arts in Denver.