The columns are made using artificial Boxwood Mat. Commercial Silk offers an outdoor version in 12" x 12" square panels http://www.commercialsilk.com/outdoor-artificial-foliages_boxwood-mat-foliage-exterior-_p_460.aspx

@ahugh - where in New York are you? We have several dealers - and believe we have the most realistic synthetic turf on the market ... and the most durable ... and we know we've got the best drainage around - The main differentiation in EasyTurf products is the MaxxFlow backing, a proprietary 100% permeable backing that drains faster and cleaner than any other turf backing - which is especially important on balcony and rooftop installations.
www.youtube.com/watch?v=rPiptLLbaqs
Let me know if you have any questions ...
Cheers!
George
http://www.houzz.com/projects/164303/Rooftop-Installation