Placing greenery and trees on buildings is not a passing fad, says designer Thomas Heatherwick in this exclusive interview.

Speaking to Dezeen at the unveiling of the Tree of Trees sculpture outside Buckingham Palace, British designer Heatherwick defended the practice of integrating trees and planting into architecture.

"Trees aren't a novelty. They're essential in life," he told Dezeen. "And so I think the architectural world can like to think things are fads but we need water, we need air, we need trees."