This article is mostly an introduction to the more common snakes encountered in U.S. gardens and how to tell the dangerous ones from the safe ones.The Non-Poisonous Species:Probably 90% of the snakes one finds in North American gardens are in the family Colubridae, of which the most common species are probably the Garter Snakes (Thamnophis spp.) or related species (e.g., Ribbon Snakes).