Bamboo can grow as fast as 1 meter per day. Alexander Vittouris, a student at Monash University, used this fact to shape the stem into the frame for this human-powered vehicle that he calls the Ajiro. The idea is to create a more sustainable means of production.
Derived from the field of arborsculpture [my link], which specialises in the specific modification and grafting of plants to create shaped structures, the conceptual design, the Ajiro, involves using these principals to create a ‘clean footprint’ urban and recreational vehicle – a grown vehicle. Using bamboo, with its rapid growth rate (as much as one meter in a 24hr period), coupled with its structural integrity make it an ideal candidate for the formation of unique urban personal mobility.
— Vittouris (2011): Ajiro – Naturally grown urban personal mobility
State of Green has a good description of the process.