At 323 acres, this park is Arizona’s largest and oldest botanical garden, founded in 1925 by mining magnate and philanthropist Col. William Boyce Thompson.
In 1917 Col. Thompson served as co-leader of a Red Cross mercy mission to Russia, where he came to understand the importance of plants as the ultimate source of a large portion of mankind’s food, clothing, and shelter. It was then that he determined to use his wealth to improve the use of plant resources. The Arboretum is one of his legacies.
Col. Thompson’s goal was to bring together plants from arid lands so that scientists and researchers could study, experiment, research, and investigate uses and attributes that made the plants unique. He also wanted the arboretum to be open to the public. By the time he died in 1930, the arboretum had already gained a reputation that extended far beyond the borders of Arizona.
Thompson’s home, the 8,000-square-foot Picket Post House, is immediately adjacent to the arboretum and is easily viewed from the far end of the main trail. It was in private hands for years but in 2008, the state purchased it with Heritage Funds and it is now under park management.
The Arboretum features plants from the world’s deserts, towering trees, captivating cacti, sheer mountain cliffs, a streamside forest, panoramic vistas, many natural habitats with varied wildlife, a desert lake, a hidden canyon, specialty gardens and more.
Cooperatively managed by the University of Arizona and Arizona State Parks, the arboretum sits at the base of the Picketpost Mountains and features a collection of 3,200 different desert plants in a unique series of botanical gardens, and a 1.5-mile main loop walking trail that roughly parallels the normally dry Silver King Wash. The main trail begins at the visitor center and quickly enters the colorful Hummingbird/Butterfly Garden, with a collection of plants designed to bloom throughout the year to attract Arizona’s diverse hummingbird and butterfly species.
A 2.5-acre Demonstration Garden shows various plants in functional landscapes; an area complete with patios, walls, shade structures, vine arbors, walkways, and rockwork. Several trails branch off from the first part of the Main Trail, so you don’t have to walk far to see the highlights, and much of the trail system is wheelchair-accessible.
The historic Smith Interpretive Center, a short walk down the main trail contains botanical exhibits and displays, and two display greenhouses feature cacti and other succulents that might not otherwise survive the winter cold at this 2,400-foot elevation.
Shorter trails cut through three desert environments. Find native medicinal and edible plants in the Sonoran Desert; plants from desert landscapes in western Texas, southern New Mexico and Chihuahua, Mexico, in the Chihuahua Desert; and flora from the Cuyo, Monte, and Chaco regions of Bolivia, Argentina, and Paraguay in the South American Desert. Look for the bizarre boojum trees from Baja California. The two specimens were brought here from Mexico in the 1920s and are the tallest ones on display in the U.S. The tall conical plants are related to the native ocotillo.
The Arboretum’s Australian Walkabout, Eucalyptus forest, South African collection, and herb garden offers more specific collections, colorful wildflowers, and varied cacti.
More than 270 species of birds have been recorded, including Gambel’s quail, Canyon wren, and black-throated sparrows, making it a prime spot for birders. A checklist of birds is available upon request. Ayer Lake and Queen Creek on the Main Trail are good places to watch for wildlife; and you may even see endangered species such as the Gila topminnow and desert pupfish.
Queen Creek cuts through the Arboretum’s bottomlands and supports the water-loving trees that take root there including Fremont cottonwood, Arizona ash, black willow, and Arizona black walnut. Take a look at the spiny branched ocotillo, the green-stemmed Palo Verde, the thorny acacias, the low-growing mesquite, and the golden-flowered agaves.
Visit the Arboretum and have your horizons expanded as to the value and use of plants and trees from arid lands for food, shelter, and livelihood, both in the past and the present.
When I walk in the desert the birds sing very beautifully
When I walk in the desert the trees wave their branches in the breeze
When I walk in the desert the tall saguaro wave their arms way up high
When I walk in the desert the animals stop to look at me as if they were saying
“Welcome to our home.”
—Jeanette Chico, in When It Rains