2016-7

Since it cannot tolerate even the slightest frost, the senita (pachycereus schottii – synonyms include Pilocereus schottii and Lophocereus schottii) is by far the rarest of Arizona’s big three cacti (the others being saguaro and organ pipe). The senita is found only in a small narrow band along the southern edge of Organ Pipe Cactus National Monument. The best place to see them is at Senita Basin, on the sheltered, south-facing slopes of the Puerto Blanco Mountains. Like the organ pipe, the senita is much more widespread in Mexico, where frosts never occur. Even in the national monument, many specimens show damage as a result of cold weather spells. Pachycereus schottii forms extensive clusters, of a hundred or more stems, up to 20 feet tall, branching from the base – like the organ pipe, but easily distinguished from the organ pipe as the senita has fewer ribs (five or six), as well as shorter, lighter and more widely separated spines, and because the top portion of each stem is covered by dark, hairy tufts, after which the plant is named. Senita (‘old’ in Spanish) comes from the resemblance to an old man’s beard. The short spines allow the bright yellowish green stem to be prominently visible. Flowers are borne along the stems, unlike the saguaro and organ pipe which bloom from the tips.

Aloe dichotoma, the quiver tree or kokerboom, is a tall, branching species of succulent plant, indigenous to Southern Africa, specifically in the Northern Cape region of South Africa, and parts of Southern Namibia. Known as choje to the indigenous San people, the quiver tree gets its English common name from the San people practice of hollowing out the tubular branches of Aloe dichotoma to form quivers for their arrows.

In the arid Arizona desert, where cacti thrive but trees are scarce, the Gila Woodpecker and this Gilded Flicker carve out nest cavities in living saguaros. Tall, old saguaros may be pocked with twenty or more nest holes, bearing witness to decades of woodpecker families. The woodpeckers excavate a new nest every year, leaving the old, now-empty cavities behind. But they don’t stay empty for long. Elf Owls, Ferruginous Pygmy-Owls, Purple Martins, and Brown-crested Flycatchers all find the slightly used woodpecker cavities superb nest sites. Saguaros benefit wildlife in other ways too, providing nectar and fruit for birds, bats, and insects. These majestic cacti are now protected by law in much of the Southwest, so that desert habitats and wildlife will not be deprived of an essential and iconic natural resource.