RESOURCES - native plants
The Pennsylvania Native Plant Society advocates conservation of native plants and their habitats and promotes the increased use of native plants in the landscape
An exceptional resource for information on native plants, including a state by state guide.
The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories.
Another great database of plant information - note several search options including "attracts butterflies"