Land is one of the scarcest resources in Singapore, a small island nation packed with more than five million people, yet walk through its business district and you will see trees sprouting from car park facades, gardens wrapped around office towers and entire walls dressed in green. This is not accidental landscaping, it is the result of a deliberate, decades long government push known as skyrise greenery, a strategy of growing plants on rooftops and vertical walls instead of only at ground level.