This courtyard-style garden pays homage to the desert-dwelling members of the world’s third largest plant family, the legumes.
Members of Fabaceae, the legume family, range in size from small annual vines to large trees, and include many common desert trees. The first legumes were planted in the garden in 1989, with funding provided by the family of Keith Taylor Sr. and several of Arizona’s green industries. Today, 121 different species are housed in the garden, represented by around 328 individual plants.
Why Legumes?
Legumes have been an important food source for humanity since the dawn of mankind. Economically, legumes constitute the world’s most important food crops, second only to grains. Seeds are high in protein, pods are often sweet yet have a low glycemic index, and the sprouts and leaves of many species are edible. The pods of our native velvet mesquite (Prosopis velutina) have been used to make flour for centuries and the carob (Ceratonia siliqua) has been cultivated for its sweet pods just as long in the Middle East. In industry, legumes provide dyes and tannins, gums to thicken foods, and quality wood for flooring, tools, artwork, and timber. Many species, such as the globally cultivated alfalfa (Medicago sativa), provide forage for the cattle and other livestock that feed the world.
With their diverse array of flowers, legumes also provide us with beauty. Here in the desert, many of our common ornamental plants, such as the orange- and-yellow flowered Mexican bird-of-paradise (Caesalpinia pulcherrima), the fragrant purple Texas mountain laurel (Dermatophyllum secundiflorum), and the hummingbird-attracting red Baja fairy duster (Calliandra californica) are none other than desert legumes.
The Desert Legume Program
The garden was conceived by the Desert Legume Program (DELEP), a joint project between the University of Arizona and Boyce Thompson Arboretum, whose mission is to both conserve desert legume biodiversity and to educate the public on the many uses of these important plants.
Most legumes possess the ability to convert atmospheric nitrogen to a usable form through an elaborate association with bacteria in their roots. This capability has allowed drought-adapted legumes to thrive in arid regions, such as the world’s deserts, where soil nitrogen is scarce. In harsh, nutrient-poor environments where most plants fail, legumes succeed. Most of our Sonoran Desert’s iconic trees, such as the mesquites, palo verdes, and ironwood, are, in fact, legumes.
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