What is Boyce Thompson Arboretum?
William Boyce Thompson made a fortune in copper, built a mansion on the hill above Queen Creek, and in 1924 founded a research garden below it to find out what plants from the world’s deserts might be useful in Arizona. A century later the arboretum is the state’s oldest and largest botanical garden: 135 acres of cultivated gardens inside a 372-acre desert property at about 2,430 feet, with more than 4,000 plant taxa and about 20,000 plants, nearly five miles of trails, and Picketpost Mountain standing over the whole thing like a stage set.
The 1.5-mile Main Trail is the visit. It leaves the visitor center through a demonstration garden, drops into the canyon of Queen Creek under cottonwoods, sycamores and a eucalyptus grove planted in the 1920s, climbs past Ayer Lake, a small reservoir with a high-desert view, and comes back through the cactus and succulent gardens. Across the wash, the Wallace Desert Garden, a major private collection relocated from north Scottsdale, adds boojums, aloes and a hillside of agaves. The labels are good, the birding is better, and in a region with almost no shade this is a place where you walk under trees. It ran as a state park for decades and is now an independent nonprofit, so a state parks pass does not apply.
What you get is the Sonoran Desert, and a dozen other deserts, explained and shaded, with restrooms and a bench every quarter mile. What you do not get is a free walk, a summer afternoon, or a wilderness; this is a garden, and it charges like one.
How to visit it right
Pay at the window or online. $24.95 for ages 13 and up, $10 for ages 5 to 12, free under 5 and for members; groups of ten or more that book ahead get $3 off a person. From June through August adult admission is $16. No reservation is needed.
Mind the hours, which move with the heat. October through March, 8 a.m. to 5 p.m. daily; April opens at 7; May opens at 6 and closes at 3 on weekdays and 5 on weekends; June through August, 6 a.m. to noon, closed Tuesdays; September 6 to 3. Last entry is an hour before closing. Closed July 4, Thanksgiving and Christmas.
Get there. Loop 101 south to US 60 east and stay on it: through Apache Junction and Gold Canyon, past Florence Junction and up the long grade past Picketpost Mountain. The entrance is on the right at Arboretum Way, about 3 miles before Superior and about 80 minutes from Old Town with no traffic. Parking is a large paved lot at the visitor center; it fills with tour buses on spring weekend mornings but turns over.
Pick the two weeks. The second half of November is the best of the year, when the Chinese pistache and the cottonwoods turn and the mornings are 50 degrees; late March is second, for the wildflowers and the first cactus blooms (see saguaro season). Any cool morning is good for the birds. Summer is a 6 a.m. affair and the hours say so. Weekdays beat weekends in spring.
Walk it counterclockwise. Take the Main Trail into the Queen Creek canyon first, while the cottonwoods are in morning shade, and finish in the cactus garden. Then cross the wash to the Wallace Desert Garden, the 13-acre collection most first-timers never find.
Water and shade. Water fountains and restrooms at the visitor center and along the Main Trail; real shade in the canyon, none in the desert and hillside sections. The picnic area is near the entrance. Bring a hat.
Accessibility. The Main Trail is mostly firm, graded surface with some grades and a few rocky stretches in the canyon; the demonstration gardens near the visitor center are fully accessible.
Dogs. Welcome on a 6-foot leash, which is rare for a botanical garden. Clean up after them.
Skip it if the price and the drive, for a walk in a garden, sound like a waste; then it is not for you, and Hieroglyphic Trail in the Superstitions is the free desert walk on the way. If a labeled saguaro, a shaded creek and a bench with a view of Picketpost sounds like a good Saturday, there is nothing else like it within two hours except the Desert Botanical Garden in Phoenix, which is smaller, closer and twice as crowded. Read the Sonoran desert plants field guide first and you will get twice as much out of it, and pair the day with the Picketpost scramble or a late lunch in Superior, or a night at Oak Flat.
A copper king’s experiment, a state park for forty years, and a garden that moved from Scottsdale
The canyon was farmed long before it was planted. Hohokam and then Salado people worked the Queen Creek drainage and the Gila below, and the Western Apache held the Pinal Mountains and the Superior country until the Army’s campaigns of the 1870s; Picketpost Mountain is named for the picket the Army kept on it to watch for them. Copper brought the next owner. William Boyce Thompson, born in Virginia City, Montana in 1869, made his fortune in mining finance, founded what became Newmont in 1916, and in the 1910s opened the Magma mine at Superior, which became one of the great copper producers of the state. In the early 1920s he built a Mediterranean-style winter home, the Picket Post House, on the cliff above Queen Creek, and from its terrace he looked down on a canyon he decided to fill with the plants of every desert on earth.
He hired the people to do it on April 1, 1924: Franklin Crider and Frederick Gibson from the University of Arizona, which the arboretum counts as its founding day. The purpose was research, not display. Thompson wanted to know which arid-land plants from Australia, Africa, the Mediterranean and Mexico might be useful in Arizona for shade, food, fiber and fodder, and the eucalyptus grove you walk through, planted in the 1920s, was a trial plot before it was a landmark. The legislature passed a bill in 1925 to let the garden incorporate; propagation buildings went up that year, the Smith Building and greenhouses in 1926, and Ayer Lake was dug in 1926 to irrigate the lower park. The arboretum incorporated on October 5, 1927 as Arizona’s first nonprofit research institution and opened to the public on April 6, 1929. Thompson died of pneumonia in Yonkers in June 1930, fourteen months later.
The lean decades followed. Crider left in 1934 and Gibson ran the place until his death in 1953; the Picket Post House was sold in 1946 to cut costs. In 1965 a cooperative agreement with the University of Arizona renamed the site the Desert Biology Station, and on March 30, 1976 a three-way agreement among the nonprofit, the university and Arizona State Parks made the arboretum a state park while it remained a private research institution, which is the arrangement most Arizonans grew up with. It was listed on the National Register of Historic Places that year, and the journal Desert Plants began publishing from here in 1979. State Parks bought the Picket Post House back in 2008. The partnership ended in the late 2010s, and the arboretum now runs as an independent nonprofit under a volunteer board, which is why your state parks pass is no good at the gate.
The biggest change in the garden’s history came from Scottsdale. H. B. Wallace, heir to a poultry-genetics fortune, had filled a private garden in north Scottsdale with thousands of mature arid-land trees, cacti and succulents from around the world. He died in 2005, his foundation could not maintain the collection, and in 2014 the arboretum agreed to take all of it. Beginning in December 2015, crews dug, boxed and trucked 5,870 plants 75 miles to Superior by pickup, flatbed and semi, the largest plant relocation the state had seen, and replanted them on 13 acres across Queen Creek with 1.5 miles of new trail and a bridge. The Wallace Desert Garden opened at the end of the decade; the eucalyptus collection, 93 taxa, was accredited in 2018 with a champion tree the staff call Mr. Big. The garden Thompson started as an experiment turned a hundred in 2024 with more plants, more acres and more visitors than at any point in its history.
Why it matters
Boyce Thompson is where Arizona first asked, seriously and with money behind it, what should grow here, and the eucalyptus, the oleanders and half the drought-tolerant landscaping in Scottsdale are downstream of the answers. It is also a rare case of a Scottsdale collection leaving town for somewhere that could keep it, which says something about land prices in the north Valley. For a Scottsdale visitor the verdict is plain: it is the best half day of walking in shade within 90 minutes, worth the $24.95 in November or March, pointless in July, and the Wallace garden across the wash is the part you must not miss.