Organ pipe cactus

Stenocereus thurberi cactus Family

(Engelm.) Buxb. Cactaceae

How many arms does a cactus need? As many as it can get, in the case of the organ pipe. Because their surface area is small in comparison to their volume, many species of cacti, including the organ pipe, experience difficulty in manufacturing enough food to stay alive. Branching is an easy way for a cactus to increase surface area, thereby maximizing its food production.

The slender arms of organ pipe are more sensitive to cold than the massive arms of the saguaro, and, as a result, organ pipe cacti are restricted to regions where winters are mild. In Arizona, the plants typically grow on rocky slopes and cliff ledges, where nighttime radiation of heat from rocks helps protect them from frost.

Organ pipe blooms in May and June. The pale lavender flowers open shortly after sunset and close the next morning. Their night-blooming habit, musky scent, abundant nectar, and lofty placement all suggest that the flowers coevolved with bats. Indeed, nectar-feeding bats are frequent visitors. In probing the deep flower tubes for nectar, bats pollinate the blossoms. The fruits, with their abundant black seeds and sweet, red flesh, are sought by a variety of animals and insects. The Spanish common name, pitahaya dulce, or sweet pitahaya, refers to the delectable fruits.

A plant of rocky canyon slopes and hillsides, organ pipe cactus can be found in the United States only in Arizona. It is common in the southwestern corner of the state and rare at a few other, widely scattered, locations. The species is widespread in northern Mexico.

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