a wilderness journal: Arizona cacti

Heading east from San Diego I descended into the hot Imperial Valley and the Sonoran Desert. Ocotillos appeared signaling entry into this desert province. After a relatively cool spring in northern California, I wasn’t quite ready to be thrust into summer temperatures. My first major destination was Organ Pipe Cactus National Monument, just north of the Arizona-Mexico border. It lies right in the heart of the Sonoran Desert.

Organ Pipe and other cacti at Alamo Canyon.

Night sky at Organ Pipe Cactus National Monument.

I first visited Organ Pipe 20 years ago, when with a class of UC Santa Cruz students we descended on northern Mexico to study the ecology of the Gulf of California. The road to Sonoyta, Mexico passes bisects the monument. I arrived after dark, and turned up a dirt road to a small campsite at the head of Alamo Canyon. It was a warm evening. I stayed up for some time photographing landscapes dominated by Saguaro cacti. A half moon shone brightly in the sky above but was gone by 4 AM when I awoke again to photograph stars and the Milky Way.

With the new day, the diversity of cacti was evident from the start. Saguaros were very common, and organ pipe cacti became more common as I made my way up the valley for a morning hike. There were menacing cholla cacti, with their beautiful golden spines covering plants like a blanket. I also recognized the prickly pear cactus, Opuntia.

The organ pipe cactus (Stenocereus thurberi) is a collection of rather large stems, emerging from a common base. The namesake of the monument, the species is more common in Mexico than in the US and has a limited presence here due to its intolerance of frost. Flowers apparently only open during the night and are primary pollinated by bats.

Saguaros (Carnegiea gigantea) were actually very common at Organ Pipe Cactus NM, growing in most regions of the monument that I observed. However, there is a whole national park named in honor of this species, and that was my next destination. Bisected by the city of Tuscon, Saguaro National Park comprises two units east and west of the city. I briefly visited some of both, catching the sunset at the west unit and doing some morning hiking at the east unit.

Saguaro cacti. Left: spines (which are actually modified leaves on cacti) on a plant at Saguaro NP. Right: An open flower on a plant at Organ Pipe Cactus NM.

The morning of my hike started off warm. I began at a trailhead at Loma Verde and hiked about 2 miles into the Saguaro Wilderness along the Squeeze Pen and Carillo trails. Saguaro, barrel cacti, and Opuntia were common. Mesquite, palo verde (literally, “green stick”), and other trees and shrubs were also abundant in the area. At Wildhorse Canyon I found pools of water remaining in a wash.

Flowering cholla cacti at Saguaro NP. At left is the pencil cholla, Cylindropuntia arbuscula.

Though not a cactus, ocotillos were common at both Organ Pipe Cactus and Saguaro NP and were frequently in bloom, their bright red flowers adding color to the landscape. At Saguaro I saw many ocotillos with leaves (some green, some senescing), a sight that may not be particularly common since these plants readily shed their leaves during times when water is scarce. It is a true deciduous desert species.

Ocotillos. Left: With leaves at Saguaro NP. Right: Hummingbird visiting flowers at Organ Pipe Cactus NM.

Wildlife was fairly common at both of these desert parks. I saw coyotes (Organ Pipe), a Gila Monster (Saguaro), a hummingbird (Organ Pipe) and other birds, a deer (Saguaro), Desert pupfish (Organ Pipe), and lots of lizards (both parks).