With a living collection of over 800 kinds of cacti, the Arboretum has become a center for the study of this family of desert plants. Most of the 800 species are displayed in the Cactus Garden and in the cactus greenhouse at the Smith Interpretive Center
Cacti are inseparably linked with the Sonoran Desert landscape; their many sizes and bizarre shapes may go far beyond our mental image of a typical cactus. There are skyscraper saguaros; paddle-shaped prickly pears; twisted, tree-like chollas; diminutive pincushions; globular barrels; and squat, branched hedgehogs. The Boyce Thompson hedgehog cactus was first identified at the Arboretum. Specimens can be seen along the trail in the Sonoran Desert Upland Natural Area.
To survive in a harsh environment has its biological costs. Many species of North and South American cacti have developed effective ways of storing and conserving water, but at the cost of scarificed growth. During infrequent rains, cacti gorge themselves, sucking up water with widespread, shallow roots. Fluted fleshy stems quickly expand to store the precious fluid. Waxy skins seal moist interiors from the sun and drying winds.
Shaped and arranged differently in each species, abundant spines and stiff hairs cast a partial and ever-changing shade over the stem, reducing heat gain. These sharp armaments also discourage browsing animals.
In spite of their harsh and forbidding appearance, cacti decorate the desert with some of its most exquisitely delicate and beautiful flowers. An immense white blossom emerges from a South American Trichocereus spachianus. Tough, thorny cacti yield delicate and beautiful blossoms. Blooms may last a single day, quickly withering to conserve precious water.
Taylor Family Legume Garden
Mesquite, peanuts, beans, alfalfa, clover, ironwood and palo verde are all members of the legume or pea family. Legumes are valuable plants in agriculture and the desert ecosystem because they add important nitrogen to the soil. The Arizona Palo Verde, Arizona's state tree, is flooded with bright yellow blossoms in April. In the dry season, the small leaves drop off to conserve water. Photosynthesizing green bark compensates for the early loss of leaves. The Taylor Family Desert Legume Garden displays and interprets arid-adapted legume trees, shrubs and herbs. Legumes are also economically important sources of timber, protein-rich food, oils, dyes and medicines.
The Arboretum is actively engaged in the experimental cultivation and propagation of economically important desert plants. Deserts and arid regions cover about 25% of the earth's land area. Worldwide, only one person in twenty is sustained by the deserts' biological productivity. As millions of acres of arable land disappear every year, deserts may yield food and fiber for a growing human population. Today, deserts are only marginally productive due to poor farming techniques, overgrazing livestock and inadequate conservation measures. With proper management and the wise use of plants and crops suited for these dry areas, deserts and semi-arid lands could yield more than they do now.
The Arboretum's Demonstration Garden presents a series of water-efficient residential theme gardens such as the one above. These exhibits show how a variety of drought-tolerant and low-water demanding plants can create shade, shelter, color and privacy in urban settings. In this display area, people are encouraged to live in harmony with the desert by choosing appropriate plant species for home and business landscaping. The result is more efficient use of this region's dwindling water supply.
Wing Memorial Garden
Pictured above, the common myrtle has fragrant flowers, leaves, bark and berries that make it a popular drought-tolerant ornamental evergreen. Thyme, oregano, dill, rosemary, chamomile along with dozens of other herbs, flowers and aromatic plants perfume the grounds of the former Clevenger homestead. Through the ages, herbs flavored food, enlivened wines, scented homes and healed the sick with soothing balms and tonics. Today, herbs are still used in many of the same ways.