I haven't tried this yet, but i'm going to work on it this fall.

Does this work for any length of time? I can see it for the photograph, but the structural integrity of the soil and root ball seems a bit questionable once you start watering something like this. (Plus the roots are exposed to drying air, w hich normally isn't good for the plants.)

This is actually kokedama and it's kinda like bonsai in that the plant will stay small. Pretty sure this holds up for a few years with care. http://www.rm-collectibles.com/Kokedama.htm

This will probably work for the longer term in the right environment with the right plants - like air plants if your climate isn't too dry, of slab mounted orchids. I doubt you can grow the lilies and other larger, flowering plants above, and force them to flower, in this type of environment. For the larger flowering plants, it will probably be successful only if fully grown & blooming plants are suspended for an event, like a party, or for as long as they last -- thinking of the installation like cut flowers/bouquet, which you know will die eventually. Also, think of the mess, trying to water, fertilize, and clean up debris from these plants.

Blarg is right, it's kokedama. Here's another link to a place which talks about the correct soil to use. It's more of a clay that you mix and then cover with moss to retain the moisture.

http://www.cutebonsaitree.com/how-to-make-kokedama-moss-ball.html

Nice to see more examples and ideas since I too loved this idea when I first saw it on AT, but it should be noted that Kimber did the original write up. Cheers! :)