A Spectacular Bloom Year for a Magnificent Desert Plant 

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Soaptree yucca (Yucca elata) is one of the crown jewels of the Chihuahuan Desert Ecoregion – a tall, stately, easily recognized species that is common in the Middle San Pedro Valley. Its distinctive plume of beautiful white flowers can be seen by the naked eye at distances upwards of a mile away. Soaptree plants can live for more than three decades and attain heights exceeding 15 feet. This is one of the few tall flowering plants in North American deserts that does not strike up a relationship with high-altitude pollinators like birds, bats, hawk moths, or bees. Soaptrees, like many other yuccas native to the West, are pollinated exclusively by only a few genera of specialized, small moths: particularly by insects known as yucca moths, (Tegeticula yuccasela or T. maculata).

The striking white plumes of soaptree yucca flower heads can be seen in great numbers this year, a special early-summer sight that part-time (winter) residents of southern Arizona may never experience.

The most common height of local soaptrees varies between 7-10 feet, but ancient grandmother plants like these can top 15 feet or more in stature.

Large, gorgeous plumes of very soft-textured, delicate, bell-shaped flowers adorn blooming soaptree yuccas.

The close relationship that this yucca has with its pollinating moths has been going on for millennia. The moths are white in color and rather small, with wingspans around an inch in width. After mating, yucca moths fly to the flowers, where they gather pollen. The pollen is carefully packed into specialized depressions on the surface of the flower ovaries. Without this stimulus, the yuccas cannot produce seeds. In return, the moths’ larvae feed on yucca seeds in the developing seed capsules.

A closer look at the flowers, whose futures depend upon an inconspicuous but crucially important moth.

This yucca is among the few desert plants that can thrive in a sand dune environment, but they do very well in other habitats as well, such as the lower elevation uplands in this valley. Unlike other yuccas, Yucca elata forms vertical rhizomes that plunge downward to depths of five feet, then grow out laterally to sprout new plants. Plant rhizomes usually grow horizontally, but this yucca’s departure from that rule enables the plants to do well in hot, dry environs.

Yuccas have a myriad of ethnobotanical aspects, for they were put to many uses by most, if not all native tribes living within the range of these pants. Yucca roots are rich in saponins, which were extracted to make effective soaps and shampoos. Many parts of the pants were consumed as food, including the flower buds, fresh flowers (eaten raw or cooked), and the flower stalks. Tough fibers from the long, linear leaves were cleverly utilized to make twine, rope, footwear, and textiles.

It has been a banner year not only for our local soaptree yuccas, but also for catclaw acacia, Acacia gregii. This specimen hosts a galaxy of highly fragrant yellow flowers whose enchanting scent forms a delightful olfactory signature characterizing the last week of May in the Middle San Pedro Valley.

full bloom alongside the catclaw plants are white-thorn acacias, Acacia constricta. The spherical, bright orange flowers exude a sweet fragrance that compliments their neighbors’ perfumes.