Common Name(s): Soap Tree Yucca

Synonym(s):

Family: Asparagaceae

Native To: Southeast Arizona to West Texas, Chihuahua and Sonora, up to 6000

Native Habitat: Desert grasslands

Growth Habit: Trunked, often branched rosette

Flowering: May - July

Distinguishing Characteristics: Yuccas are distinguishable by their tough and fibrous leaves, less succulent than agaves. The soaptree yucca is trunked and has narrow, fibrous leaves. Flowers of the yuccas are large, white, waxy, and cup-shaped, and the fruits are hard capsules that split into three segments.

Natural History and Cultivation Notes: Yuccas of the southwest have a unique pollination story. Females of one particular moth species mate, take pollen from one yucca plant, fly to another, lay eggs in the yucca flower, then pack the pollen onto the stigmas of the flower. The moth is both harming the yucca, because the developing larvae eat seeds, and helping the yucca, because the mother moth ensures that the flower is pollinated. This is considered a classic and important case of a mutualism, where both partners in an interaction benefit - the moth benefits by having food for its young, and the plant benefits by having a reliable pollinator. This sort of interaction works as long as the cost is not too great to either partner. Some seeds must remain unharmed and it must not endanger the moth too much to spend its time gathering and delivering pollen.

Ethnobotany: Native Americans know the Soaptree Yucca to be an extremely functional plant. Its common name comes from one of its most important uses: the roots, when mashed yield a soapy substance called amole, that can be used as shampoo or soap for washing. In addition, almost every part of this palm-like tree, including fruits, flowers, seeds, and stalks, are edible and are rich in vitamin C. Cattle also enjoy eating the yucca and during droughts its leaves, trunks, and stalks can be used as a last resort livestock feed. Another popular use of the Yucca is the textiles made from its leaves. The fibers of the slender yet sturdy leaves have been used by Native Americans to weave a variety of functional products including mats, baskets, ropes, nets, sandals and clothing. The yucca is pollinated almost exclusively by the yucca moth, which depend on its seeds as a primary food source.

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