Boyce Thompson Southwestern Arboretum

Flower & Garden Magazine, March-April, 1997 by Ellen Henke

East of Phoenix, Arizona, along the Gila Pinal Scenic Highway, the stark beauty of the landscape is intensified by the shadows cast in the dramatic light of sunrise or sunset. The vision of a rocky desert landscape punctuated by stately saguaro cacti (Carnegiea gigantea), the patriarchs of the desert, with their arms stretching heavenward, will be etched in your memory forever.

Just west of Superior, Arizona, in the upland division of the Sonoran desert, you will discover the Boyce Thompson Southwestern Arboretum. Nestled in the shadow of Picket Post Mountain, the 325-acre arboretum represents perhaps the world's finest collection of dry climate plants. More than 2,400 water-conserving species -- including plants that are native to the American Southwest as well as Africa, central Asia, Australia, China, Mexico, the Near East and South America -- grow together in perfect harmony.

This botanical gem, in a picture-book setting surrounded by mighty canyon walls, was founded by William Boyce Thompson. The Montana-bred entrepreneur and financier amassed a vast fortune through the acquisition of mineral-rich properties, including the Magma mine at Superior, which ultimately became one of the greatest copper producers in the United States.

In 1917, while leading a Red Cross expedition to Russia that took him through arid parts of Siberia, Thompson became aware of mankind's dependence on plants. Considering his own fascination with plants and recalling his mother's struggle to nurture life from the dry Montana soil, Thompson concluded to create a plant research facility to benefit humanity. In 1924 he created the Boyce Thompson Institute for Plant Research, which today is located at Cornell University in Ithaca, New York.

As Thompson spent more time at his mines, he came to love the Arizona desert and decided to build a plant research station where scientists from around the world could study drought-tolerant plants and distribute their seeds. As a bonus, this living museum would restore beauty to a land that mining had ravaged. Unfortunately, Thompson did not live to see his passion fully realized. He died June 27, 1930, before the dedication later that year of the Boyce Thompson Southwestern Arboretum.

Thompson's legacy has survived to become a significant resource for knowledge about desert plants and a demonstration garden for those interested in desert landscaping. Cacti of every conceivable form rise from the earth, ranging in height from 1 inch to 20 feet. Frost-tender species are nurtured in the greenhouses.

This desert garden is interesting in all seasons. It is especially splendid in late spring, when the arid-climate plants, ranging from trees to prostrate succulents, put on a compelling show of colorful, exotic and elaborate blooms. Some blooms are ephemeral, lasting only one day; others linger to the fascination and delight of visitors.

A pair of Sonoran boojum trees, now over 30 feet tall and reputed to be the tallest in the United States, mark the low path through the garden. If your visit is preceded by rainy fall and winter seasons, annual flowers will be dotted along the arboretum floor and slopes for springtime color. Fragile larkspurs, goldfields and phacelias provide a marked contrast to the towering saguaros, prickly pears and agaves.

The arboretum teaches visitors a great deal about plant habitats and ecology. Hardwood trees and lush, water-loving plants, unexpected in the desert landscape, thrive where Queen Creek runs through the picturesque canyon. This intermittent stream cuts a path through handsome volcanic rock formations, creating an environment that sustains the plants. Characteristically elusive, it flows beneath the desert floor, providing life-giving water to a spectacular grove of Australian eucalyptus trees, towering 100 feet or higher above the desert floor. The environment is ideal for several other varieties of eucalyptus, as well as some huge Aleppo pines. A collection of palms is also located near the eucalyptus grove.

A beautiful path draped in olives and pomegranates leads to a secluded collection of aromatic herbs in the Wing Memorial Garden. In this surprisingly romantic setting, climbing roses ramble over canyon walls near a wonderful old stone cottage that is partially carved out of the cliff.

Indeed, gardeners in arid regions may choose from an interesting array of landscape plants, The Boyce Thompson Southwestern Arboretum teaches us to create landscapes that reflect regional growing conditions, choosing native and exotic plants that thrive in our climates and soils without much intervention. The arboretum also conveys the importance of plants that are nursery-propagated, not collected from the wild.

The water required to irrigate the arboretum is pumped from a well and stored in Ayer Lake, a beautiful garden oasis that attracts and sustains a variety of birds and butterflies, many of which pollinate the desert flowers. If you have time, take a few minutes to hike the high trail through the garden and enjoy the perspective it offers.