In preparation for bloom time and the arrival of the birds and the bees, ironwood trees shed most of their leaves. I picture it like a young man stepping out of his t-shirt and flip flops and pulling on a wedding day tux. The result is stunning, as the ironwood is transformed with mauve, white and grey blossoms. It’s a fleeting impression as the flowers soon give way to chubby brown seed pods.
Desert residents are treated to this spectacle every spring, yet this cycle of leaf, flower, fruit is only the most visible performance of an ironwood tree. The trees we admire for their pretty flowers are actually the VIP’s (VIT’s) of the desert. Each individual orchestrates soil, moisture and temperature conditions to provide for a myriad of other species, both plant and animal, actually creating pockets of life in an unforgiving land.
The work begins underground. When an ironwood seedling sends its first roots into the impoverished desert soil, it emits chemical compounds that attract Rhizobium bacteria that form nodules on the roots. This makes nitrogen available in the root zone.
The newly photosynthesizing plant also releases compounds that spur the growth of fungi that spread like a mat under the surface of the soil. This mat connects to the root system and grows on the sugars secreted by the plant. In turn the fungi provide the tree with nutrients and protection from disease. Other microorganisms come to feed on the bacteria and fungi and to colonize and further enrich the soil.
Above ground the ironwood tree spreads a canopy that creates precious shade and lowers the ambient temperature. More plants begin to sprout in this shelter, thriving in the nitrogen rich soil. Sixty five different species of plants will grow beneath an ironwood tree.
Many species of insects are drawn to the tree. Birds, reptiles, amphibians and mammals come. The animals eat leaves, nectar, seeds, pods and each other. Over the tens and hundreds of years that an ironwood can live branches, bark and dead material from other plants build up around the tree, creating hidey holes for nests and burrows and holding moisture in the soil.
Conservation scientist Dr. Gary Nabhan says, “The list of residents living under a 45 foot ironwood reads like the Who’s Who of the Sonoran Desert.” I love to think of this tree forming partnerships with other plants and other beings from one-celled bacteria to javelinas, creating together a diverse and resilient community.
When the Rains Come, Alcock
The Lost Language of Plants, Buhner
Ironwood: An Ecological and Cultural Keystone of the Sonoran Desert, Nabhan and Carr