‘It seems that everyone’s talking about “sustainability” these days, with the usual thought being that, as exterior designers, good environmental stewardship must be one of our main missions.’ That’s the way Bruce Zaretsky opened his On the Level column five years ago before asking a string of key questions:  ‘But what is sustainability?  What do watershapers need to do to encompass this philosophy?  As important, what does it mean to our clients, and where are