The freewheeling flora are made up of hardy stonecrops (Sedum species) frequently planted on green roofs, and other low maintenance veggies such as lettuce and zucchini.
"So far, the Bus Roots gardens are designed to live mostly on rain, with the occasional watering in case of drought," said Castro.
Besides adding life to drab city buses, the Bus Root project hopes to provide a source of fresh veggies in urban food deserts, absorb carbon dioxide, insulate the buses from summer heat, suck up storm water, and provide a connection to nature for city-dwellers.
"I would love to expand and experiment with other buses in other cities," said Castro.
The BioBus, part of the Bus Roots projects (Shane Ramkinssoon)
The BioBus pick up passengers in New York (Shane Ramkinssoon)
A close-up of Sedum in the Bus Roots garden (Bus Roots info packet)