In Britain, the Horticultural Trades Association a few years back issued this flyer, researched by the Royal Botanic Gardens Kew.
Plants speed up recovery from illness.
A study has shown that hospital patients overlooking a garden recovered faster and needed less medication than those overlooking other buildings. Plants will help prevent skin cancer. The shade thrown by trees and climbing plants helps reduce the amount of ultra-violet radiation we are exposed to. Plants help reduce vandalism. Research on a housing estate in London showed that the presence of gardens is one of the most powerful factors in curbing crime and vandalism.