Fall foliage colors arrive in the mountains around Tucson sometime in mid October. A good place to observe them is in the canyon along Bear Wallow Road near Summerhaven in the Santa Catalina Mountains, where many beautiful Bigtooth Maples (Acer grandidentatum) with their autumn leaves of gold, orange, and scarlet can be seen among the dark evergreens.

I think that all colors of Bigtooth Maple leaves are at their most beautiful when backlit by the sun. Although not as brightly colored as the scarlet leaves, the gold and orange leaves are more beautifully translucent in the sunlight.

These native trees can grow to about 40 feet (12.2 m) tall. Bigtooth Maples are very close relatives of Sugar Maples (Acer saccharum). Like Sugar Maples, Bigtooth Maples are high in sugar content and can be tapped in late winter for the sugary sap used to make maple syrup. The characteristically brilliant red color of maple leaves is due to high concentrations of anthocyanins, which are produced in the presence of direct sunlight and excess sugar in the leaves.

Along with Bigtooth Maples, another similar species of maple tree occurs here in Arizona, the Rocky Mountain Maple (Acer glabrum). Unlike the more finely toothed leaves of Rocky Mountain Maples, the 3 to 5-lobed leaves of Bigtooth Maples have mostly smooth margins with just a few large teeth.

Bigtooth Maple leaves have smooth upper surfaces and soft, velvety lower surfaces. In spring and summer, the leaves are a bright, translucent green.

Given that most of the trees in the mountains around Tucson are various species of evergreen, larger scale displays of fall foliage colors in our mountains are limited to some hillside patches of Quaking Aspens and the few, moist canyons where deciduous trees like Bigtooth Maples are common.