Learning about Sonoran desert plants in the Phoenix East Valley
Usery Mountain Regional Park is a 3,648-acre park set at the western end of the Goldfield Mountains in Phoenix Valley’s east side. The park is home to a variety of Lower Sonoran Desert plants and animals. When I set out to attend a morning event entitled “Desert Plants”, I expected a pleasant walk amid beautiful scenery. I didn’t know if I would learn anything new about desert plants beyond what I’d already picked up on other tours. But I did. The great diversity of plants which thrive in the harsh conditions of drought and heat in the Sonoran desert means there is always more to learn.
The hour long tour focused on how desert plants adapt to these harsh conditions. The very knowledgeable Range B encouraged questions of all kinds about the desert and, as a result, the scope of what we covered was broader than just the plants’ adaptive abilities. We even busted a few myths.
One of the myths to be busted was that you can survive if stranded in the desert by cutting into a cactus for water. Cacti do store water, but it is very acidic and can be toxic to humans. It may result in diarrhea and further dehydration. The prickly pear pads sold in grocery stores or found in Mexican restaurants are generally young pads which are less acidic. Also, cooking leaches out the acids.
The spines of the cacti serve a few purposes, one of which is protection from predators. However, some animals, such as javelinas and pack rats, have figured out how to nibble around the spines.
The spines help provide cacti with shade. And in some cases, as with certain varieties of cholla, they help with propagation. The barbs are sensitive to nearby movement and easily loosen from the rest of the plant to attach themselves to a passerby. When the detached segment later falls to the ground, it takes root and forms a new plant. The plants have been nicknamed “jumping cholla” because of the ease with which segments detach from the plant, but they don’t really jump.
I was familiar with information Ranger B provided about the creosote bush. The bush gets its name for the smell it gives off, which is said to be like creosote. We were told to cup some leaves in our hands, blow directly on them three times, and then smell. The leaves give off a definite musky smell. It is known as the “smell of the desert”, because the smell permeates the valley during rains. The leaves are waxy, coated with a sticky resin which protects against ultraviolet rays, reduces water loss, and repels animals. The bush is covered with yellow flowers in spring time.
Some desert trees, such as the palo verde, are drought-deciduous, meaning they lose their leaves in the dry season to conserve water. Even when they are in bloom the leaves of the palo verde tree are thin so the trees loses less water through transpiration. Broad leaves capture sunlight to make food through photosynthesis. In the absence of broad leaves, the green bark on the palo verde tree has taken over much of the photosynthesis work.
One of the others on the tour asked Range B about fire. I grew up on the Canadian prairies. Although little of the natural tall grass prairie remains, I did know that fire was important to its rejuvenation. Fire is not needed for rejuvenation in the desert. The spaces between plants act as firebreaks helping plants survive fire. In many settled parts of the Valley, non-native plants have invaded that space. Spaces still exist in Usery Mountain Park. All plants in the park are native. No watering is done, except for the landscaped area immediately around the Nature Center building.
The Desert Plant Walk took place on the quarter-mile Desert Hawk trail behind the Nature Center just inside the park. Usery Mountain Regional Park has twenty trails of varying length and difficulty, for hiking, mountain biking, and horseback riding. There are camping facilities, day picnic areas, a couple of covered playgrounds, and an archery range.
The park hosts dozens of events each month, covering a variety of topics. A sample includes edible plants, moonlit walks, myth busting, all about bighorn sheep, and beginning desert hiking. The cost of the events is included in the park entrance fee. I enjoyed my Desert Plant Walk so much I hope to be able to get back and take in some of the other events.
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