I tried doing this last Summer and the plants fell out. I just used garden liner, and I think that this article gives better advice. I'll pick up some coco liner instead and that will probably look better anyway!
Backyard Inspiration - Ideas for Garden Lovers! I love the pebbled steps! They can curve around and lead you to a secretive place around the home or maybe a small nod around your yard to another bird bath, bird feeder or a beautiful spray of flowers
The spectacular views of the wisteria flowers at Kawachi Fuji Gardens, in Kitakyushu, Japan is another shining example of Japanese perception of beauty and arch . Surreal Wisteria Flower Tunnel in Japan ,Chinadaily Forum