Autumn at Superior's Arboretum

COLONEL THOMPSON'S DESERT GARDEN HARBORS THE EXOTICS OF FIVE CONTINENTS

I'd been overcome by a late-breaking yearning for fall, an unpredictable impulse that sometimes afflicts even we desert rats. I've never much missed shoveling snow, snugging children into long johns, or fighting frozen engine blocks, but at some point each year I'm generally overcome by an unexpectedly intense yen for golden cottonwoods, crimson walnuts, and yellow sycamores. Should such a sensation overcome you in Phoenix during the death throes of November or the first crystallizing of December, there is a spot nearby that can soothe your angst. Long after the aspens have quaked their last on the fringe of Flagstaff and the explosion of fall has fizzled from the Four Corners down to Mount Graham, this one lingering patch of color glitters in Colonel Thompson's desert garden 60 miles east of Phoenix and down the road from the old mining town of Superior. Sitting there atop a fused outcrop of volcanic residue, I watched wind rustling through the golden surge of cottonwood, sycamore, Chinese pistache, and ash trees. The

tempestuous sea of fall-drenched trees lapped against the base of my hill like breakers turned molten by the sunset.

The Boyce Thompson Southwestern Arboretum spread out all around the peninsula of stone on which I perched. To my right, cacti from all over the world squatted, reared, and lurked spiny, wattled monsters with misshapen forms crafted to withstand the rigors of the deserts of five continents. To my left, gigantic red, gold, and yellow trees gathered from streamsides throughout the world jostled one another in an intense struggle for sun, water, and space along the banks of Queen Creek.

I savored the cool caress of the sun-softened winter breeze, balanced atop my 30million-year-old hummock of ash left over from the cataclysm that crafted the jagged Superstitions range and the outlandish cliffs, buttes, and volcanic stumps of looming Picketpost Mountain. Some 70 years ago, iconoclast, miner, and entrepreneur Col.

William Boyce Thompson built a house on a nearby crag and bought up some 350 acres of spectacular Sonoran Desert running back up into the rugged depths of Queen Creek Canyon. Thompson acquired the title "Colonel" in 1917 when he helped lead a Red Cross medical supply mission to Russia in the wake of the revolution.

A longtime lover of plants, Thompson hired a botanist to lay out his garden, which gradually evolved into a spectacular Nature preserve and plant research center. He eventually established, with the assistance of the University of Arizona and the Arizona State Parks Board, a foundation to maintain and expand the arboretum for the general public.Sitting on my rock, I let my eye wander across the swaying treetops, enjoying the fall sampler that included both the stalwarts of a Sonoran Desert stream and colorful immigrants like the flaming Asian pomegranates and the lurid Chinese pistaches.

This perennial flush is the legacy of one of Nature's most intriguing schemes. Trees adapt two basic approaches to winter: they either lavish resources on producing tough, frost-resistant leaves or whip out huge quantities of flimsy leaves they can afford to lose. These thin, broad leaves soak up energy through the salad days of summer but wither with winter.The early chill of fall triggers a cascade of physiological changes as the trees draw nutrients out of the vulnerable leaves then seal off the now dispensable leaf. The whole process is orchestrated by the release of certain chemicals, which produce the dramatic change of colors with the seasons. The green chlorophyll retreats into the stems to be replaced by other stress-related chemicals that come in reds, yellows, and browns.

Of course we're inclined to mourn the dying leaves, but that's because we think in straight lines instead of the circles with which Nature builds. In fact, fall isn't deathbut merely another turn of the wheel. The blaze of the trees, the leaf litter, and the relative hush of winter offer just another transition, encouraging diversity, especially in an ecological treasure trove like the arboretum.

DESERT GARDEN

The arboretum's managers maintain meandering trails through about 100 acres of gardens open to the public and conduct on-going studies of plants, insects, and animals throughout the total 350 acres and an adjacent 1,000-acre swath of the Tonto National Forest. About 80,000 visitors a year wander along the shaded trails and creek, poke through the crowded cactus garden, add unexpected birds to their lifetime lists, pick through the bookstore and gift shop, and collect stray facts about desert plants.

The arboretum also shelters 207 species of birds, 48 species of reptiles and amphibians, and 37 species of mammals - including the occasional mountain lion that leaves its startling footprint along Queen Creek as it patrols for deer, javelinas, and small mammals. The 800 varieties of cacti, 3,000 drought-resistant plants, and remarkable trees, shrubs, grasses, and flowers from across the world make the arboretum a botanist's dream and a hiker's delight.

I treated myself to a complete circuit of the guided trail, clutching the booklet that offered insights into the leafy, thorned, succulent world of plants at one numbered stake after another. I realized as I started how little credit we give plants for their remarkable adaptations, although we all live on their forbearance. They've penetrated the mystery of sunlight, contriving to produce energy from a distant star.

We're all merely parasites on that remarkable ability, breathing the oxygen they produce as an afterthought and clinging to the end of the food chain which starts with the magic of chlorophyll. So I resolved to spend the day appreciating plants and looking for signs of the complex interactions by which they keep the rest of us alive.

The newly developed legume garden provided one of the first stops, an array of drought-tolerant, desert-loving plants that sprout bean pods, bundling their seeds with their own life-support system. These varieties of mesquite, paloverde, acacia, and others made it possible for most of the Native American desert cultures to survive in a harsh environment, supplying a seasonal bounty of nutritious foods that could be turned into an array of edibles and stored for long periods.

The loop trail led on into one of the most peculiar cactus gardens I'd ever encountered, bristling with the thorned glory of golden barrels, mutated monstrosa, shaggy hedgehogs, and an array of strange species that seemed stolen off the set of a science-fiction movie. Meandering, looped side trails led through a sampling of Mohave, Sonoran, and Chihuahuan desert plants - each distinctive and equally weird - like the improbably upside-down boojum trees of Mexico.

My amble then took me to Ayer Lake, a reedy man-made duck pond which feeds the arboretum's irrigation system and harbors a sampling of endangered desert fish, little darting wigglers whose ancestors evolved remarkable adaptations to the scattered, unpredictable, hot-and-cold-running seeps, springs, and streams of the desert. They've been driven out of most of the riparian areas that survive by water diversions, cattle, and foreign fish. I sat awhile on a bench, watching some feathered paddlers widgeons, mallards, and a wayward teal bobbing for treats in the shallows.

Then I trudged up a gentle hill and stopped to admire the sea of waving trees below in the rugged gash of Queen Creek. Winding down past Thompson's fortress on the hill, I strolled through the soothing canopy of the streamside forest, savoring the stream's murmur, the dappling of the late light, and the overwhelming variety of plant life.

The Sonoran Desert regulars seemed like old friends, enormous cottonwoods, sycamores, and willows, crowded together in a great-trunked display of the bounty that lined so many desert streams before we turned the wood and water to our own uses. But all along the trail, I encountered exotic interlopers: trees with thorns, bark of cork, and branches with smooth, sinuous shapes.

DESERT GARDEN

The climax came when I rounded a corner to find myself standing in a small grove of Chinese pistache trees, arrayed in a mind-numbing splendor of red and orange. I sat mutely in the midst of the garish grove, trying to sort through the rush of feeling inspired by the glowing exuberance of color.

It seemed like a gushing sunset, caught in midglory and prolonged. The leaves glimmered in the breeze, shifted like drifts of jewels on the ground, and fluttered through the air like dying dreams. I don't know how long I sat there, seeking the riddle to the psychological mystery of fall. But at some point I became the phenomenon, losing track of time and any interest in mysteries beyond the play of light in the leaves.

I'd been nearly lulled to sleep by the sound of the wind in the trees, when a flicker of iridescent color caught my eye. Velvet black and brilliant blue provided an unexpected note of grace in the first shiver of December no doubt the pipevine swallowtail butterfly that arboretum Curator Dr. Carol Crosswhite had told me about a powdery ecological parable. The swallowtail butterfly lives in a tight ecological triangle that includes a vampire fly and the pipevine, a crafty flower with a bad reputation.

The butterfly lays its eggs only on the pipevine, a small brown plant with cork-screwed, pipe-shaped flowers, once used by Indians to treat snakebite and by snake-oil salesmen to treat everything from typhoid to smallpox. All these concoctions depended on the bouquet of chemicals the plant produces to keep from being eaten.

However, the purplish caterpillar of the pipevine swallowtail evolved a digestive tract designed to gobble pipevines, and it can even concentrate the plant's defensive chemicals in its body to make itself uneatable. Oddly enough, although the swallowtail's caterpillar can survive only on pipevines, the butterflies don't actually pollinate the pipevines.

That function is performed by a small bloodsucking fly that mistakes the pipe-vine's musty, flesh-colored flower for the ear of a mouse. The fly buzzes into the flower, lands, and slips down through a forest of downward-pointing "hairs." The hairs trap the fly until it is covered with pollen, then they wilt to allow the fly to escape and carry the pollen to another plant.

Sure enough, my fluttering guide soon led me to a pipevine. I felt a rising surge of gratitude to Colonel Thompson as I stood there, breathing the plant's cast-off oxygen, identifying with the hungry caterpillar, the bloodsucking fly, and a butterfly smelling of flowers. Then I found a comfortable seat and let the day deepen as I savored a second chance at fall and counted passing butterflies, wind-tumbled leaves of gold, and my many blessings.

WHEN YOU GO

The Boyce Thompson Southwestern Arboretum is about an hour east of downtown Phoenix, three miles west of Superior. To get there from Phoenix, take the Superstition Freeway east to Apache Junction, then turn southeast, right, onto U.S. 60.

The arboretum offers several hiking trails, none of them too difficult. The High Trail is narrow, and as its name implies offers a superb view of the fall foliage canopy below. Watch for the arboretum's "eucalyptus grove" and the multiarmed 200-year-old saguaro. Don't miss the gift shop and retail plant section. Take a lunch to enjoy at the picnic area, where you will likely spot a variety of curious and hungry birds and squirrels, as we did. Best times to go? Year-round, keeping in mind that late autumn and early winter deliver fall color and spring brings wildflowers. In March the arboretum throws a big party honoring its part-time buzzard residents, and every April there's a big plant sale.

Wear comfortable walking shoes, take binoculars, a hat, and don't forget the sunscreen. The desert gardens sit at an elevation of 2,400 feet, so expect temperatures to be a little cooler than in Phoenix.

The arboretum is open daily except Christmas, 8 A.M. to 5 P.M. Admission is $4, adults; $2, ages five to 12; and free, four and under. The following areas are wheelchair accessible: visitors center, parking areas, access routes/walkways, rest rooms, water fountains, picnic areas. Trails are rated as usable to inaccessible due to slope and terrain.

For more arboretum information, write 37615 U.S. Highway 60, Superior, AZ 85273-5100; telephone (602) 689-2811. To inquire about accommodations in the area, call the Globe-Miami Chamber of Commerce, (520) 425-4495; or the Apache Junction Chamber of Commerce, (602) 982-3141.