Tuesday, November 17, 2015

Boyce Thompson Arboretum - A Primer

Boyce Thompson Arboretum is not only the oldest and largest botanical garden in Arizona, it is the fourth oldest west of the Mississippi River. It’s spectacularly situated, drawing on hundreds of acres of borrowed scenery, courtesy of the surrounding Upland Sonoran Desert vegetation and mountains of Tonto National Forest. A travel guide, like Fodor’s, might correctly describe this part of the desert as “saguaro-studded,” and, indeed, it is.

Anyone who has traveled to Globe, or Roosevelt Lake, or the White Mountains of eastern Arizona, has passed the Arboretum, perhaps without even noticing. It’s easy to whiz by, particularly because much of the grounds lies below your car’s line of site along US Highway 60, and because many of our plants are hidden from view between two tall volcanic ridges. If you find yourself driving through the historic mining town of Superior, you just passed the Arboretum about three miles back.   

If you’ve never visited Boyce Thompson Arboretum, then you’re not one of the 80,000 people who did last year, nor are you likely to be one of our 5,000 members. It also means that you haven’t received our quarterly 32-page member magazine, our weekly eNews, or attended any of our expert-led birding walks or photography classes. The big question is: How has a world-class destination like the Arboretum, with an international collection of arid land plants from deserts around the world, not become that must-see destination on your bucket list?

It’s a question best resolved by loading up the car and heading east towards the base of Picketpost Mountain, where Queen Creek and Silver King Wash converge, and where 100-feet-tall volcanic cliffs rise above three miles of trails and 40 unique gardens and plant exhibits.  This is the spectacular geologic location where multimillionaire investor and mining entrepreneur Colonel William Boyce Thompson was perceptive enough to create “the most beautiful garden of its kind in the world” over 90 years ago. The 392 acres of gardens and natural areas contain over 13,000 (soon to be nearly 20,000) plants from arid land regions across the planet, with the largest collections hailing from Australia, South America, and the Sonoran and Chihuahuan deserts of North America.  

Most of the tallest, broadest, and most mature trees, shrubs, cacti, and other succulents were planted during the 1920s and 1930s, and they continue to have a dominant presence throughout the plant exhibits at the Arboretum. A skyline of red gum Eucalyptus trees (several, like “Mr. Big,” are over 150 feet tall) were planted from tiny saplings, and now support the nightly roosts of up to one hundred Turkey Vultures who call the Arboretum home for six months each and every spring and summer.

Perhaps our most famous—and unusual—plants are our boojum trees. These bizarre-looking plants are stout, columnar relatives of Arizona’s native ocotillo that were brought to the  Arboretum from Mexico in 1925. The name “boojum” was coined by a University of Arizona plant scientist who, after seeing a forest of these trees (sometimes described as upside down carrots) in their native habitat along the Sea of Cortez on the west coast of Sonora, Mexico, named them after a mythical character in the Lewis Carrol poem, The Hunting of the Snark.  

It does rain in the Sonoran Desert, and the Arboretum receives its share of it, with two thirds falling in the winter months (about 10 inches), and the remaining six inches during the summer monsoon. And, as we all know, when it rains in Arizona, it pours, so crossing either Queen Creek or Silver King Wash used to be impossible when they filled from heavy rain events. With the construction of the Benson Outback Bridge across Silver King Wash and the 130 feet long Berber Suspension Bridge over Queen Creek, the only chance today of getting wet today is from the rain above, not from the water below.

The eight-acre Australian Desert Exhibit was completely redesigned in the early 1990’s and now includes eight defined plant communities from the arid outback with authentically replicated Aussie buildings, an Aboriginal ceremonial area, and an ethno-botanical garden. Most recently, an Australian “jump-up” called Papuana Pass was completed, as was a new grove of curvaceous  bottle trees that are natives of Queensland, Australia. Plants from seven other desert biomes are also on display, including those from South Africa, Turkmenistan, and the Mediterranean region.  

Easily seen from the highway is a thatched-roof, shade structure known as a “quincho.” It’s constructed from materials imported from Argentina and is thought to be the only one of its kind in the U.S. It forms the entrance to the South American Desert Exhibit where more than a dozen large Argentine saguaros and other large cacti populate a slope in much the same way that they might appear in the Monte Region of their native habitat in northern Argentina. These fetching, columnar cacti contribute their bulk and character to 700 other South American plants added to this exhibit since 1993.

Even though Boyce Thompson Arboretum has created exhibits from eight of the world’s deserts, it also has a number of specialty gardens that feature plants more related to each other than to a particular region of the world. It’s the Arboretum version of plant nepotism and one example is the Taylor Desert Legume Garden, where plants in the bean family are grown and arranged according to their importance as food, fodder, industry, medicine, and ornamentals. Other gardens include a collection of fragrant, old garden roses in the Heritage Rose Garden and the historic masses of golden barrels and other cacti and succulents in the two-acre Cactus Garden.

The Hummingbird and Butterfly Garden (known affectionately to our staff as the Hum-Butt Garden) and the Wing Memorial Herb Garden are two slightly different specialty gardens because they are designed with plants combined by their usefulness rather than their genetics. A Children’s Garden is adjacent to the Arboretum’s original visitor center—now called the Smith Building—where kids can become a human sundial, experience a living rainbow, find their way through a bamboo maze, and even make a frog croak.

Newly planted this year in the 2.5 acre Demonstration Garden is a garden designed to provide food and shelter for birds, bats, butterflies, moths, and other insects. We provide the plants, and the critters attracted by them carry pollen from one flower to another, producing fruits and seeds, which in turn attract other wildlife. It’s a match made in heaven, and, to no one’s astonishment, we call it the Pollinator Garden.

One of the most important developments in the Arboretum’s 90 year history is the acquisition of the entire 12 acre plant collection of Wallace Desert Gardens in north Scottsdale.  Over 6,000 mature trees, shrubs, saguaros and other cacti—even a dozen more boojum trees—will be transplanted and trucked 75 miles to the Arboretum during the next several years. Hundreds of plants have already been moved, ready to be planted in a never-before-developed area near the Demonstration Garden.  A new bridge will span Queen Creek and a pavilion greenhouse will be built to display the 20 feet tall (and still growing!) columnar cacti and other plants that won’t survive without some protection from the cold and/or direct sun.    

With a world-class collection of arid land plants, frequent photography and horticulture classes, weekend bird, reptile, butterfly, tree, and geology walks, festivals that celebrate plants, music and culture, year-round plant sales, and a “top-shelf” bookstore, Boyce Thompson Arboretum has evolved to become one of the leading botanical gardens in the country. With the addition of the Wallace Desert Gardens collection, our plant collection is now attracting worldwide attention.  

But if you’re just looking for a beautiful way to spend the day in an untamed natural environment, or to walk your dog (yes, dogs on a leash are welcome!), or to munch on lunch in our shady picnic area, we’re the perfect place to unwind and reconnect with the natural world. Remember: We’re close to the city, yet far enough away.