Standing tall

In the Arizona Upland portion of the Sonoran Desert, the plant that commands most of the attention is the iconic Saguaro with its tall stature and dramatic form. In moving from the desert valleys toward the surrounding higher terrain, the plant community becomes increasing dominated by grasses and presents a decidedly low stature aspect. There is one plant, however, that towers over its neighbors in these vast arid grasslands in much the same way as the Saguaro dominates the desert valleys. In southern Arizona that plant is the Soaptree Yucca (Yucca elata). Other species of Yucca replace it in other regions of the grasslands. They, like the Soaptree Yucca, can become quite massive and grow to a height of fifteen feet or more, and can be seen standing tall in the sweeping mid-elevation seas of grass.

Douse the sun

A lone isolated storm moves across the desert, trailing a curtain of rain beneath. As luck would have it, this storm cell moved over part of the Mulberry Fire and aided firefighters in controlling its spread. From this vantage point, the showers seem to douse the sun, a fitting metaphor for its fortuitous appearance over the wildfire.

The arboreal desert

The Sonoran Desert of Arizona shares many of the same flora and fauna as the Chihuahuan Desert further to the east. Both deserts also share a similar climate and the same basin and range topography. Despite these similarities however, the Sonoran Desert presents a different visual aspect than its cousin to the east, largely because of the presence of taller stature plants. Towering Saguaros dominate the Sonoran Desert’s Arizona Upland to the extent that they become a feature of the landscape, but in addition, there is a profusion of small desert trees such as Palo Verde,Ironwood, and a number of others. This produces a striking contrast to the low stature vegetation which dominates the Chihuahuan Desert, and because of all its desert trees, the Sonoran Desert is sometimes called the arboreal desert.

Texas Canyon

East of Tucson, between the small towns of Benson and Willcox, Interstate 10 traverses a saddle between the Little Dragoon Mountains on the north side of the highway and the Dragoon Mountains to the south. This area, known as Texas Canyon, is famous for its spectacular boulder-strewn landscape. As the quartz monzonite boulders of Texas Canyon have weathered over time, they have tended to become increasingly rounded. This process of eroding and fragmenting rock is called exfoliation. Today, Interstate 10 follows the old stagecoach route of the Butterfield Overland Mail which operated here during the years just before the Civil War, allowing visitors to penetrate the heart of this fascinating area of gigantic rock outcrops.

Cold storage

As February progresses, things start warming up in the low deserts of Arizona, and the procession of rainy winter storms moving in from the Pacific starts to wind down, soon to grind to a halt. There is still some moisture left behind, however, held in cold storage as it were, high in the mountains that make up the Sky Islands. The water, in the form of ice and snow, is released gradually and helps to tide the land over until the arrival of the summer monsoons. This February photograph is from Bear Wallow at 8,000 feet in the Santa Catalina Mountains.