Flora and Fauna News

Saguaro Cactus
Flowers Open for Business

By Michael Plagens
Sonoran Desert Sciences

PHOENIX, Az. ----- The huge, white, waxy blooms of the Saguaro Cactus (Carnegiea gigantea) are now blooming. Cacti growing at about 300 m elevation are at peak blooming now; the peak will advance up slope with a few flowers still appearing through mid June. Like many white-flowered plants, the flowers open just after dusk. This is usually an indication that important pollinators are about at night, and in the desert that's a good bet given the searing daytime temperatures.

Sanborne's Long-nosed Bat (Leptonycteris sanborni) is the nighttime pollinator that several Cereus-type cacti rely on. The bats, too, rely on the cactus for nectar and pollen, and then may help the cactus yet again by feeding on insects that could damage the developing fruit. The magnificent flowers remain open through the following day attracting bees and birds.

Ironwood Too!

PHOENIX, Az. ----- Together with the Saguaro Cactus, the Ironwood Tree, (Olneya tesota), adds a splash of brilliance to late spring, when hot temperatures and drying winds are rapidly desiccating the earlier spring growth and wildflowers. The flowers are almost white to a deep lilac color and can be borne in great abundance on some trees. Some ironwoods, each year, will be almost completely devoid of flowers, holding out for a possible better season next year.

Ironwood National Monument was created last year to help conserve the stands of ironwood that lie to the northwest of Tucson. Without protection, urban sprawl could overtake a significant portion of this important desert tree's habitat. Ironwoods provide for many wildlife species including the Cactus Ferruginous Pygmy-Owl (Glaucidium brasilianum).

A Saguaro Cactus with a bounty of blooms.
Photo taken in the Phoenix Mountains, May 22, 2005.

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