The Senita looks very similar to the Organ Pipe cactus, but the senita has a dense cluster of spines near the top of mature branches.
The spines on the senita look like whiskers to some people, hence the name “Old Man.” But the name has some controversy about it. According to the Arizona-Sonora Desert Museum:
The word “senita” seems to be derived from the Spanish root meaning “old,” in which case it roughly translates as “little old woman.” This is rather descriptive of the gray-bristled mature stems. But “senita” is not a legitimate Spanish word. The Mexican name of the cactus is borrowed from the original Indian name, sina. Some feel that the Spanish vernacular name should therefore be spelled “sinita.”
Only the mature branches have the spine cluster. The senita is far more frost tolerant than the organ pipe, allowing it to survive farther north and to higher elevations. Senitas can grow to 13 feet tall. Pink, nocturnal flowers about an inch in diameter emerge through the bristles from April through August. The flowers have an unpleasant odor. If pollinated, the flowers mature into marble-sized red fruits with juicy red pulp. Native people ground the seeds of the fruit into a nutritious mush, and the pulp was boiled down to syrup.
Senitas are pollinated by a moth that lives among the spines. The moth larvae survive by eating the developing fruit. This example of mutualism is similar to that of certain yuccas and their pollinating moths.
Senitas are long-lived cacti. According to an ASDM report: “When sites in Baja California photographed in 1905 were revisited in the 1990s, nearly every senita was still present.” The natural range is from extreme southern Arizona, to Sonora, and Baja California.
Both senitas and totem pole cactus share the genus and species name Lophocoreus schottii (aka Pachycereus schottii). A subspecies name of monstrosus is added to the totem pole cactus in some classifications.
ADI articles on other desert plants:
Chiltepin peppers, spice and medicine
Saguaro Cactus Icon of the Sonoran Desert
Yuccas provide food, fiber, and soap
The Jojoba bush and its valuable oil
Mesquite trees provide food, fuel, medicine, and more