Check this out

Check out Mark Dion's exhibit from 2002 working with real plants in sculpture.
http://www.tanyabonakdargallery.com/exhibit.php?exhibit_id=80

Chris Maynard - amazing feather artt
http://www.featherfolio.com/

Bruce and Norman Yonemoto - some very environmentally conscious works here.
http://www.janm.org/exhibits/yonemoto/installation.html