With the addition of the Wallace Desert Garden, Boyce Thompson Arboretum (BTA) now holds collections of desert plants from the United States, Mexico, Australia, Madagascar, India, China, Japan, Israel, South America, the Middle East, Africa, the Mediterranean, and the Arabian Peninsula-all told 4,025 taxa and 20,000 plants within 135 acres of gardens. Situated on 372 acres of scenic upland Sonoran Desert with nearly five miles of trails, BTA is Arizona’s oldest and largest botanical garden and one of Arizona’s top tourism sites.