Massive Plant Collection Finds a New Home

Boyce Thompson Arboretum

by Tom Domek and photos by Tom and Kyra Domek

Huge. Impressive. No words better explain it. The agreement to transport some 5,000 to 6,000 desert plants from one botanical garden in Arizona to another is a hugely impressive endeavor. That's what's happening in the Phoenix metro area. A super-sized collection of desert flora is being dug up, transported by truck, and transplanted on the grounds of a top-tier arboretum.

For decades, the Wallace Desert Gardens, otherwise known as the Wallace collection, has sat on 12 acres in Scottsdale, AZ. Unfortunately, an endowment to operate the collection has nearly run dry. Enter Boyce Thompson Arboretum some 75 miles away. Two years ago, executive boards from each garden agreed to transfer all of the desert plantings from the Wallace collection to the grounds at Boyce Thompson, a herculean undertaking unlike any other ever attempted. And we're not talking about just little plants either; some individuals are as tall as 25 feet and require a 72-inch hand-built wooden container.


Anyway, let's drop some sunshine on this thing. The Boyce Thompson Arboretum just west of Superior, AZ, is a 392-acre park along Queen Creek. The Arboretum attracts some 85,000 visitors each year, and is well-regarded for the sheer number of worldwide desert species growing there. It is the largest botanical garden in Arizona, part of the state park system, and includes a trail system easily traversed by those with physical handicaps. The Arboretum is well tenured, too, having been first established back in 1924 by its namesake, Boyce Thompson, a mining engineer who amassed a fortune through his mineral interests in the area's Superstition Mountains.

So while Boyce Thompson has long been a public park, the Wallace collection has always been basically private. The Wallace Desert Gardens is linked to one of the great family names in U.S. agriculture. The collection is named specifically for Henry Browne (H.B.) Wallace, a noted agriculturalist who was well-known for developing hybrid lines of chickens. In turn, H.B. was the son of Henry Wallace, President Franklin Roosevelt's Secretary of Agriculture and, later, vice president, who helped FDR lead the nation out of the devastating effects of the 1930s Dust Bowl. H.B.'s grandfather—Henry Cantwell Wallace—also served as Secretary of Agriculture under the Warren Harding and Calvin Coolidge administrations.

In the mid-1980s, H.B. and his wife Jocelyn retired to Scottsdale. Two years later, they began purchasing one-acre plots where H.B. could develop and design a private garden in the dry, desert landscape. Over time, the Wallaces amassed a remarkable collection, including thousands of plant species, such as gaping agave and stately saguaros. They built a pavilion covering one and a half acres. This “Inner Garden” protected scores of desert plants, including columnar cacti from the extremes of weather. They surrounded their 6,000-square-foot Cactus Pavilion with cactus and additional succulent plants from around the world, including Madagascar, Mexico, Australia, the Arabian Peninsula and elsewhere. Eventually the Wallaces set up an endowment to maintain their private garden.

Sadly, H.B. passed away in 2005. Then, during the economic downturn beginning in 2007, the endowment began to shrink. The Wallace family soon realized that they would be unable to preserve the Wallace Desert Gardens far into the future. When media picked up on the story, the executive director of Boyce Thompson Arboretum, Mark Siegwarth, recognized that perhaps their botanical garden could absorb the Wallace collection. Siegwarth approached the Wallace family, and an agreement was inked in 2014 that directed the transfer of the Wallace Desert Gardens to Boyce Thompson Arboretum State Park.

Finally, in August 2015, the first Wallace collection plants rolled into Boyce Thompson Arboretum. Meanwhile, the one-acre lots H.B. and Jocelyn originally purchased are being sold. As a result, the transfer of the Wallace collection must be completed by this coming July.

The logistics of the move are pretty interesting. Dig teams at the Wallace collection site in Scottsdale typically hand dig each plant, even the larger specimens such as yucca and saguaro. Once they've trenched around the plant, the wooden panels used for transport are pieced together in the hole. Heavy equipment is used to lift each boxed plant onto a semi-truck. After a three-hour trip from Scottsdale, the plants are unloaded from the semi and placed outdoors or, for some plants, in one of six shade houses recently constructed to receive them. Staff at the arboretum continually water the plants and check them for shock.

Jeff Payne is a certified arborist at Boyce Thompson. He and his staff make use of the wells on site to water the new additions. Because they'll receive up to 2,200 boxes of plants, it may be many months before all of the plantings are completed. Some of that has to do with weather, but Payne says weather actually works in their favor with Wallace collection additions. “Our conditions are almost identical to those found at the Wallace site in Scottsdale. We receive about the same amount of rain, our dew point is about the same, and so is our humidity.” An added advantage is that the arboretum is nearly the same elevation as the Wallace site. Furthermore, the plants at Boyce Thompson aren't subject to the heat island effect caused by urban sprawl that occurred on the Wallace site. Therefore, plants at the arboretum can have a beneficial “cool down” at night, something they get much less of in Scottsdale.

Payne says that the loss rate due to transport has been “very low. We're only losing about two or three percent of our plants.” By the time the transport is complete, Payne estimates that approximately 2,200 boxes of plants will have been moved. By then, well over 100 semi trips will have been completed, he says.

The addition of the Wallace collection into the collection at Boyce Thompson Arboretum is pretty exceptional, too. According to the January 2016 Boyce Thompson Arboretum newsletter, the Wallace collection includes “1,650 taxa (species, cultivars, hybrids, varieties, etc.) of which over 50% are new to the existing collection of the Arboretum and Desert Legume Program. The combined collections place the Arboretum within the top 25 botanical gardens in the United States in total taxa.” The newsletter also points out that more than 200 of these taxa “are globally unique... found at no other botanical garden—anywhere.” The combined collections also now rank the Arboretum as first in the world in the number of desert legume taxa. More than 250 taxa in the combined collection are considered globally threatened, ranging from vulnerable to critically endangered in the wild, the newsletter says.

Arboretum staff will also be establishing more than a mile of new hiking trails with a bridge over Queen Creek, which will lead visitors into terrain devoted to the Wallace collection. The area will be called the “Wallace Garden Collection” and will be located at the west end of the arboretum. Parts of the trail will be handicap accessible.

The gigantic effort going into the transfer of the Wallace Desert Gardens to the Boyce Thompson Arboretum is truly significant. It helps preserve the efforts of the Wallace family in behalf of desert flora, and helps preserve precious biodiversity. Overall costs of the project, which is being funded by the sale of the original Wallace site in Scottsdale as well as donations, will probably top “several million,” according to Cathy Babcock, director of horticulture at Boyce Thompson Arboretum.

She says that visitors “will be extremely excited by the new hiking trail and collection.”
Payne adds, “We're all about conservation and preservation. We conduct important research here too. The Wallace collection fits right in to what we do.”

Boyce Thompson Arboretum State Park is open year round. For more information, call the park at 520-689-2723. Boyce Thompson Arboretum is located a couple miles west of Superior, AZ, at 37615 E. U.S. Highway 60.


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