(Proboscidea altheaefolia and Proboscidea parviflora)
Most commonly known as "devil’s claw," this desert hitchhiker is also called "elephant tusks" or "unicorn plant." Each name refers to the plant’s seed pod. The first two names allude to the woody capsule, which splits open at one end into two curved claws or horns. Before the pod splits, the green, fleshy fruit superficially resembles a unicorn’s horn. The generic name "Proboscidea" comes from the Greek word "proboskis," a term for an elephant’s trunk, literally meaning "a way to provide food." Altheaefolia refers to the leaves, which are similar to the marshmallow plant. Parviflora means small flowered.
Two species grow in this region, the perennial P. altheaefolia, and the annual P. parviflora. Two-inch long, bright yellow flowers grace the perennial species. They protrude above the large (two-inch wide), sticky shiny green leaves. Plants hug the ground and emerge from a tuberous root.
The annual variety has pinkish-purple flowers and similar leaves, which are both sticky and stinky. In contrast, the smaller flowers are more hidden by the large (up to three inches wide) foliage. Devil’s claw flowers are similar to those of the snapdragon.
Both species possess the characteristic fruit, which starts as a fleshy green, somewhat banana-shaped structure, but soon dries to produce the clawed, woody capsule, which is generally less than five inches long. Upon splitting, the capsule begins to release black seeds, which can take several years to germinate. Seeds are rich in oil and protein and are edible, as are the fleshy fruits, which some folks pickle.
With such large flowers, the perennial species is generally pollinated by big bees, like carpenter and bumble bees, but a small bee, Perdita hurdi, also gets in on the act, in a most provocative manner. Females land on an unopened flower, crawl under the corolla, cut open a wee hole, clamor in, and obtain pollen. She then goes in search of a open flower to find nectar, and often, she encounters what could be described as a randy male Perdita hurdi. When she lands, he pounces upon her and copulates with her. During the frenzy, her pollen may brush the flower’s stigma and complete the pollination process.
Warm weather triggers growth of both species of devil’s claw. They bloom in summer, although P. altheaefolia does not flower every year. Devil’s claw leaves are heliotropic (sun tracker). During the morning, leaves may be flaccid but soon become turgid and turn toward the light. As the day progresses, leaves will turn a complete 180 degrees, following the sun.
Seed capsules such as those of the devil’s claw evolved as a way for the plants to spread their seed. Hooves of large grazing animals provide the perfect "foothold" for the claws. Cattle eat the fleshy fruit.
Devil’s claw grows across the Sonoran desert, from southern California into Texas and south into Mexico. They occur most often in disturbed soils and may be common in agricultural fields or alongside roads. Due to its fleshy taproot, the perennial species is less water dependent than the annual.
The Tohono O’odham of southern Arizona have cultivated a variety of devil’s claw, P. parviflora var. hohokamiana, that possesses several unusual characteristics. Instead of black seeds, the plants produce white seeds, which germinate more quickly than the wild species. In addition, the dried capsules are longer, up to 15 inches, and more flexible than non-domesticates.
Ethnobotanists believe that this domestication is one of only a handful that occurred for wild native plants north of Mexico. Furthermore, it appears that women were responsible for this process. When cattle became widespread in the desert, O’odham women, who used the pods in their basketry, started to plant devil’s claw in protected areas to prevent livestock consumption. Over time, they chose seeds that produced the longer capsules and seeds that germinated faster. Gary Paul Nabhan, writing in his fascinating Gathering the Desert, calls this domestication "plant wifery."
This cultivar is so important for basket making that it has spread to over 25 native cultures, many far beyond the feral plant’s original range.
In the July 1908 issue of Technical World (now Popular Mechanics), one Harry Dunn fancifully described a rootless cactus, which rolled about the desert for eight to nine months of the year before it took root and sent out shoots. New growth exactly resembled the parent. He wrote: "When the damp season is over these roots shrivel up and finally fall off the parent cactus, [which] dying from the constant sapping of the circle of young ones around it, leaves this circle a hedge of thorns."
When legendary desert botanist Forrest Shreve saw this article and the accompanying photos he quickly realized that Dunn had in fact described "a bunch of fruits of the unicorn plant [while] the reckless disregard of truth displayed by the author excites admiration." This appeared in the September 1908 issue of Plant World.