Links
- Greenroofs.com
- Green Roofs for Healthy Cities
- Michigan State University Green Roof Research
- Penn State Green Roof Research
HORTICULTURE
- American Horticulture Society
- American Public Gardens Association (APGA)
- GardenWeb
- Horticulture World
- National Gardening Association
- Texas A & M Horticultural Site
- The Royal Horticultural Society
- USDA Plant Hardiness Zone Map