the whole skin of the building is based on french botanist patrick blanc’s greenwall or vertical garden. the plants are inserted into a geotextile material and are provided with all the nutrients by a series of tubes. so the answer is you don’t have to water them, it’s done automatically. the species used are mosses in the “cavern” below and evergreens for the rest of the building. it’s not grass even though it looks like it, so it doesn’t need to be mowed either.