Filed Under Agriculture

Boyce Thompson Arboretum

Reviving the Desert after Decades of Mining

Boyce Thompson Arboretum is Arizona’s oldest and largest botanical garden.

The 378-acre Boyce Thompson Arboretum (BTA) sits at the foot of Picket Post Mountain and is bordered by Highway 60. It is three miles from the small mining town of Superior, Arizona. Colonel William Boyce Thompson, who made his fortune in mining, founded the Arboretum as arguably the world's first dry lands arboretum. The mission of the arboretum is to study plants from sub-arid regions around the world, so it is also home to about 20,000 plants of 4,025 taxonomic species (about 30% of which are rare and endangered) from around the globe. The garden contains plants from the United States, Mexico, Australia, Madagascar, India, China, Japan, Israel, South America, the Middle East, Africa, the Mediterranean, and the Arabian Peninsula.

It may seem paradoxical that a man who made his riches mining would have a soft spot for the environment. Still, Thompson grew up gardening as a boy in Montana and, from a young age, observed how the fumes from copper smelting damaged his crops and vegetation. As a member of an American Red Cross relief mission, he visited Russia before and after the Russian Revolution, earning the honorary title of Colonel from the Red Cross. Traveling through Siberia, he observed the ingenuity of locals who survived on scarce vegetation in an arid land, showing the potential of arid plants to solve food supply shortages. This inspired him to create the Boyce Thompson Institute for Plant Research in Yonkers, New York (now at Cornell University), to investigate the potential that plants had for the betterment of mankind. He continued this mission by establishing an arboretum in the Sonoran Desert he had come to know and love. His intentions were ambitious, stating, “We will bring together and study the plants of the desert countries, find out their uses, and make them available to people."

Officially incorporated as Arizona’s first non-profit research organization in 1927, Boyce Thompson Arboretum opened to the public in 1929. Constructed in the shadow of the Picket Post mansion, Colonel Thompson’s winter home, the arboretum was closely associated with the University of Arizona throughout its history. In 1965, the arboretum entered into an official partnership with the University to establish the Desert Biology Station and further research efforts. In 1976, the Arboretum and the University of Arizona entered an agreement with Arizona State Parks, where the Arboretum would be simultaneously a non-profit research center and a State Park. This agreement lasted until 2019, when the Arboretum once again became an independent non-profit.

Its modern mission echoes the sentiments of Colonel Boyce Thompson as it strives to “inspire appreciation and stewardship of desert plants, wildlife, and ecosystems through education, research, and conservation.” Its dedication to sustainability can be seen in the arboretum, which functions as a living museum open to the public and researchers to learn from the rich ecosystem. Research on medicinal uses for plants, geographic surveys, and wildlife studies occur on the same trails as bird watching and elementary school field trips.

BTA houses nationally accredited collections of eucalyptus trees, desert legumes, and southwest oaks. It also houses the country’s largest longneck eucalyptus, “Mr. Big.” At 177 feet tall and with a circumference of over 22 feet, Mr. Big was added to the National Register of Champion Trees in 2018. He immigrated from Australia at three in 1926 when he was just six feet tall. He is 100 years old and happily rooted adjacent to his wife (a eucalyptus), Mrs Big.


Boojum Trees at Boyce Thompson Arboretum
Boojum Trees at Boyce Thompson Arboretum BTA is home to plant species from around the world, including the Boojum Trees (Fouquieria columnaris) originally found in northwestern Mexico.  Source: "The Boojum Tree: Origin, Adaptations, and Interesting Facts," Boyce Thompson Arboretum, accessed February 25, 2024.  Creator: Boyce Thompson Arboretum
The Picket Post House
The Picket Post House Colonel Boyce Thompson’s home above the arboretum. This photo was taken shortly after the completion of the main house in 1924. Known as the Picket Post Mansion or "Castle on the Rocks," it was Colonel Thompson's winter retreat until his death in 1930. Thompson donated the house and land to the Arboretum in 1928. Source: Boyce Thompson, "The Unexciting Truth About William Boyce Thompson’s Picket Post Mansion," Thompson Family History, n.d. accessed May 16, 2024 <>. Date: 1925
The Greenhouse and Smith Building<br />
The Greenhouse and Smith Building
These greenhouses have been recently renovated to include a new irrigation system that allows horticulturalists to control and monitor the water that the plants inside receive. The renovation maintained the original look of the greenhouses as built by Colonel Boyce Thompson. Source: Melissa St. Aude, "The Greenhouses at Boyce Thompson Arboretum Getting a Makeover," Pinal Central, March 29, 2021, accessed February 16, 2024. Date: March 29, 2021
View from the trail
View from the trail A view of the surrounding mountains from the arboretum's main trail. The view shows areas of the Arboretum threatened by the Telegraph Fire in June 2021. The fire made it to the edge of the Arboretum but did not damage any collections. After the fire, the Arboretum was victim to flash flooding as an after effect of a wildfire. Source: Collection of Erin Craft Creator: Erin Craft Date: November 6, 2023
Mr.  Big
Mr. Big This 117-foot Longneck Eucalyptus tree is the largest of its species in the United States, with a circumference of over 20 feet! Mr. Big is an unofficial mascot of BTA. Source: Private collection of Holly Barnard Creator: Holly Barnard Date: November 06, 2023
On the Trail
On the Trail BTA placed a collection of signs along their main trailing showing a "then and now" perspective to celebrate the 2024 Centennial. The collection used photographs from the 1920s placed in the same location today. This example is on the main trail and shows the growth of the vegetation since the 1920s. Source: Private collection of Holly Barnard Creator: Holly Barnard Date: November 6, 2023
An example of Sustainability
An example of Sustainability These light fixtures are sustainably fashioned from boxes used to transport plants into the arboretum’s Wallace Garden, demonstrating BTA's commitment to sustainable practices. Source: Private Collection of Holly Barnard Creator: Holly Barnard Date: November 6, 2023
Desert flora located in the Wallace Garden
Desert flora located in the Wallace Garden The entire Wallace Garden Collection was transferred from Scottsdale, AZ to Superior in 2015. Source: Private Collection of Holly Barnard Creator: Holly Barnard Date: November 6, 2023


37615 E. Arboretum Way Superior, Arizona 85173


Holly Barnard, “Boyce Thompson Arboretum,” Salt River Stories, accessed June 24, 2024,