Boyce Thompson Arboretum

Boyce Thompson Arboretum, established in 1927 near Superior, Arizona, is the oldest botanical garden in the state and one of the oldest in the American Southwest. Founded by copper mining magnate William Boyce Thompson, the arboretum covers 392 acres in a scenic desert canyon setting at approximately 2,400 feet elevation along US Route 60, where a canyon microclimate cooler and moister than the surrounding desert supports an extraordinary density and diversity of plant life. The arboretum displays approximately 3,200 plant species from desert regions worldwide, with particular strength in Sonoran Desert flora, Chihuahuan Desert plants, and arid-adapted species from Australia, South Africa, and the Mediterranean basin. The main trail system covers approximately 3.5 miles of paths through distinct plant communities: the Sonoran Desert nature trail passes massive saguaro cactus and towering ocotillo; the mesquite bosque recreates a riparian desert woodland corridor; the Cactus Garden presents hundreds of cactus species from across the Americas in a concentrated display; and the Ayer Lake shoreline trail offers birdwatching over a small reservoir fed by Queen Creek. The arboretum's bird list includes 272 species recorded on the grounds, making it one of the best accessible birdwatching sites in central Arizona. The facility is operated jointly by Arizona State University, the University of Arizona, and the Boyce Thompson Arboretum Foundation, lending it a distinctly research-oriented character. Admission is substantially lower than Phoenix's Desert Botanical Garden, and the canyon setting is more intimate and less developed. Spring wildflower season from mid-February through April is the most spectacular period, when desert annuals bloom across the canyon floor and early migrant birds arrive.