There’s no better time to take a hike in the Sonoran Desert than…right now! After last summer’s “nonsoon,” the rainfall we’ve experienced in the Tucson area has brought relief and rejuvenation to the desert landscape. However, it’s also brought destruction in the form of flash floods, sometimes causing damage to walking trails, so check the status of the trails before you head out.
The Tucson Mountains, the Desert Museum’s backyard, is an especially rewarding place to spend a morning exploring the plant life of our region. We suggest you walk slowly and take the time to savor the details of the landscape!
On your walk, you’ll find every color of the rainbow. Don’t forget to bring a camera or sketchbook, and if you have one, a magnifying glass. Look for ripe red wolfberries (yes, they are edible!), bright Arizona poppies opening with the rising sun, delightful pops of yellow blooms from slender janusia, lush green in the form of vines, spike mosses, native grasses, ferns, and plump cacti, and bright blue canyon morning glories, all growing amidst volcanic rocks in deep shades of red and purple.
What makes the Tucson Mountains so special? While this mountain range has similar elevation, climate, and vegetation to the range within Organ Pipe National Monument and White Tank Regional park, the Tucson Mountains are more biodiverse due to the higher, on average, summer rainfall. And with summer rains come summer ephemerals (aka annuals)! These plants don’t stick around, so we encourage all readers to go visit your favorite outdoor places as soon as you can.
In the Tucson Mountains, you’ll find the typical desert scrub of the Arizona Upland subdivision of the Sonoran Desert where the Tucson area is located, but the vegetation here is particularly rich. The varied terrain of these mountains creates many different microhabitats, each with unique combinations of sun exposure, slope angles, rock and soil types, and plant communities. The great abundance of plant species that thrive here make it an absolute must-see when exploring the region on foot.
What to look for on your walk:
One might not imagine moss and ferns growing next to prickly pears or pincushions, but after heavy rains, this is exactly what you’ll find! Look for Astrolepis cochisensis, the Cochise scaly cloak fern, and the spike moss Selaginella arizonica growing together with several kinds of cacti on north facing rocky outcrops. Spike mosses are not true mosses, but are actually related to ferns! Spike mosses have basic vascular structures seen in some of the most ancient plant species on earth.
Do you delight in seeing colorful flowers adorning the desert? Because blue is a rare color to find in flowers, encountering one is a special treat. Look for vibrant Ipomoea barbatisepala, canyon morning glories, as well as the sunny slender janusia, Janusia gracilis, blooming on leafy vines growing on cacti like cholla or prickly pear.
A somewhat more inconspicuous but ubiquitous plant to look for is Boerhavia coulteri, or Coulter’s spiderling, an ephemeral herb blooming in great quantities after summer rains. Whip out your magnifying glass to examine the tiny, delicate flowers.
Tidestromia lanuginosa, known as wooly honeysweet, is a distinctive low-growing plant whose leaves are covered in soft dense hairs, creating a whitish woolly appearance. The stems are dark red, creating a beautiful color contrast. Find this plant at lower elevations in valleys with sandy soils.
Want to observe the world like a botanist?
Take notice of what kind of terrain you see certain plants growing in, and what other plants they tend to hang around with. These are called plant communities, and just like human communities, they tend to organize themselves into neighborhoods based on sun exposure, soil/rock type, and terrain. As you walk through the Tucson Mountains, notice these different plant communities:
- Creosote and bursage community, found on the flatter and lower slopes.
- Saguaro and palo verde community, the dominant association of plants found at all elevations of this range. Palo verde trees are a common “nurse tree” for young saguaros. A multilayered mixture of understory plants can be found growing in this community including several kinds of cacti, many herbaceous perennials and small shrubs.
- Ironwood trees merge gradually between the two previous communities and are present on the lower and more gentle slopes. They don’t tolerate frost well, so you won’t find them at upper elevations.
- Jojoba scrub community, found on rocky north facing slopes as you go up in elevation. Look for jojoba, brittle bush, prickly pear, cholla, and ocotillo.
- As you reach the higher peaks like Wasson Peak, semi-desert grassland merges with desert scrub. Many perennial grasses are present, and also a few shrubs associated with higher elevation grassland or chaparral.
- Desert riparian communities, where most of the biodiversity is concentrated, grow along the many washes and drainages. Look for velvet mesquite, whitethorn acacia, desert hackberry, catclaw acacia, canyon ragweed, and yellow monkeyflower. These canyons even support some semi-aquatic plants growing in a few places where the water table is close to the surface!
The more you explore and observe, you might come to realize that plants that are common along one trail might not be common at all on a different trail, and vice versa. Botanists use the phrase “locally common” to describe this phenomenon. Different plants will dominate the landscape in different areas, creating a unique look and feel to each trail and wash in this range. While this means that it’s necessary to visit many different areas at different times of year to get a true picture of region’s floral biodiversity, it also means there is a lifetime’s worth of exploration awaiting you!
Written by Elena Makansi.