Each summer in Tucson, white-winged doves acquire bright-red beaks — a sure sign that the fruit of the saguaro cactus is ready for harvest.
Perhaps more than any other forms of vegetation, saguaros epitomize the rugged spirit of the Sonoran Desert. But what many people don’t know is that many wouldn’t survive at all without the desert ironwood tree.
On Saturday, May 10, the Tucson Audubon Society will hold its 23rd-annual Ironwood Festival, a celebration of a rugged tree that makes so much life possible. Amid blooming ironwoods — if the trees adhere to schedule — participants will learn about a handful of the 500-some plant and animal species that find refuge and sustenance in its presence.
Because this year’s event falls on International Migratory Bird Day, festivities will begin with two early morning birding field trips.
Those who don’t mind rising earlier than the sun can meet at the Jack-in-the-Box parking lot on Ina Road just east of I-10 for a 6 a.m. departure to bird-sighting spots across Marana or meet at Catalina State Park at that same time to count bird species at the park.
Starting at noon, four 20-minute lectures at the Mason Audubon Center will detail the importance of the ironwood tree for migratory birds and other life-forms.
Like other so-called “bean trees” – the palo verde and the mesquite – desert ironwoods fix nitrogen and, when their leaves drop to the ground, enrich the soil. They also provide life-giving shade for vulnerable seedlings from the punishing desert sun. Saguaros grow under them, using them as “nurse trees.”
Unlike those other legumes, ironwoods live to be 800 to 1,000 years old. Not only that, it is believed that they can stand tall about 800 years after they die. Their wood is so dense it sinks, and scientists believe that its toxicity makes it virtually immune to decay.
But despite their rugged desert appearance, ironwoods show a greater sensitivity to the perils of the modern-day desert than other legumes. Because they grow slowly, they undergo a huge setback when land is cleared for housing developments.
Also, they react badly to drought.
Photos taken Mason Audubon Center about 20 years ago show more ironwoods than the property contains today — about 350, said Lia Sansom, who works at the center. The center’s mesquites and palo verdes, conversely, have increased in population.
The Mason family, which donated the property for the center, recognized the importance of the ironwood tree and asked that the land be used specifically for its preservation. To that end, the center limits visitation to the park. The Ironwood Festival is its one large-scale public annual event.
The festival’s lunchtime lectures will be followed by an education fair, which will run from 2 to 5:30 p.m. Entire families can enjoy half-hour presentations featuring live appearances by raptors, amphibians, reptiles, arthropods and a bobcat.
In the evening, folk-rock musicians will gather for concert that, in the past, was a separate event titled “An Evening Under the Ironwoods.” The concert, which will run from 5:30 to 9 p.m., will include the bands A Ray of Hope, Eb’s Camp Kookin, and the Ironwood Allstars.
Also at the festival, three 15-gallon ironwood trees will be raffled, local amateur photograpahers will present their work in an avian photography display, and vendors will sell food.
Most importantly, organizers hope participants will gain a greater respect for the area in which they live.
“What we’re trying to do is get people interested in the history of this natural habitat in ways they can really relate to,” said Paul Green, the center’s executive director. “The more people we have who are advocating for the survival of the habitat, the better.”
The desert ironwood tree, or palo fierro, ranks among the most ecologically important plant species in the Sonoran Desert.
• More than 500 species of plants and animals live in its habitat, including the lesser long-nosed bat, desert tortoise, chuckwalla, desert iguana and saguaro cactus.
• It shades young flora from the dangerous heat of the Sonoran Desert and enriches the soil by fixing nitrogen.
• Its wood is one of the hardest and heaviest in the world, and it is remarkably resistant to rotting, perhaps because its heartwood is rich in toxic chemicals that make it essentially non-biodegradable.
• Its flowering period lasts 10 to 18 days.
• Though it is not endangered or threatened, its populations dwindle annually. Its habitat faces threats due to urbanization.
What: Ironwood Festival, featuring International Migratory Bird Day
Where: Tucson Audubon Society Mason Center
When: All day Saturday, May 10