Though not technically a part of the Sonoran Desert, frozen tundra is found close by. The peaks above Flagstaff, Arizona, rise more than 12,600 feet, leaving the timberline far behind. In this remote area, and only 45 miles from from saguaro cactus growth on the northern border of the desert, is a continually frozen area that hosts some of the same plant species found in Alaska.
Slopes of the upland Sonora, found primarily in Arizona and parts of Mexico, are characterized by growths of coniferous and deciduous forests. Higher elevations play host to conifers, pines and other related types of trees, while the foothills flourish with aspens and oaks. A chaparral-type of vegetation, taking the form of evergreen shrubs, is found in the transitional area between the mountains and the more stark regions commonly associated with deserts.
Since it is a desert, you can expect blistering hot areas overgrown with cactus plants and other thorny types of shrubs. Sand dunes abound in the area where California, Arizona, Baja California, and the Mexican state of Sonora come together. This part of the Sonoran Desert would generally be considered the most inhospitable to human habitation.
The southern end of the region, including Baja California and Sonora, sprouts a tropical deciduous forest for a brief stretch of time during the summer rainy season, but presents a mostly dry and leafless appearance the rest of the year. This area of the Sonoran Desert shows a splash of color and greenery that seems to defy the scientific classification as a desert region.