Public Gardens

Chanticleer
Longwood Gardens
Morris Arboretum - of the University of Pennsylvania. Official arboretum of the Commonwealth of PA.
Scott Arboretum - of Swarthmore College
Temple University
Tyler Arboretum

Plant Selection and Care

Missouri Botanical Garden Plant Finder - Look up, view a photo, read about over 7,500 plants
Oregon State University - Landscape plant photos and information.
University of Delaware Botanical Garden
Penn State University Cooperative Extension - Horticulture/Gardening Page
University of Connecticut Plant Finder
Pennsylvania Horticultural Society Gold Medal Plants
United States National Arboretum - see their introductions. Great site for Crape Myrtles.

Insects and Diseases

Ohio State University Cooperative Extension
PSU - Woody Ornamental Insect, Mite, and Disease Management