ECHO (Fighting World Hunger) serves as an agricultural support network to the world. They provide global farm tours of their North Fort Myers research facility and answer questions about plant care, use, and propagation. ECHO’s Tropical Fruit Nursery makes many of these plants available to US gardeners.
Tropical & Sub-Tropical Fruit Trees. A Hawaiian source for tropical fruit trees. Site has descriptions, including space requirements.
Top Tropicals – rare tropical plants.
Southern Exposure Seed Exchange offers more than 700 varieties of vegetable, flower, herb, grain and cover crop seeds–many unusual, Southern heirlooms, yacon, basils, and amaranths, peanuts, southern peas, naturally colored cotton, collards, okra, roselle, turnip greens, corns for roasting and meal, and butterbeans.
The World Agroforestry Centre (ICRAF) is a CGIAR Consortium Research Centre. ICRAF’s headquarters are in Nairobi, Kenya, with six regional offices located in Cameroon, China, India, Indonesia, Kenya and Peru. Covers land care and cultural /environmental issues. Includes a Tree Seed Suppliers Directory, indexed by country (you may have to get a government permit to import seeds).