Panayoti Kelaidis is the Curator of Plant Collections at Denver's renowned Botanic Garden. He also designed the Rock Alpine Garden.
Kelaidis is a plantsman who studies and lectures worldwide on rock garden plants.
His books include
Flourish: A Visionary Garden in the American West
High and Dry: Gardening with Cold-Hardy Dryland Plants
Rocky Mountain Traveler - a Guide to Locating Rocky Mountain Wildflowers
Colorado Traveler Guidebook: Wildflowers
If you have any interest at all in succulents, take a look at his photos at his Picassa album