The Joshua Tree and the Yucca Moth

Mating

• As the Joshua tree flowers in spring, male and female yucca moths break from their cocoons. After a male and female yucca moth mate on a Joshua tree flower, the female moth begins to gather pollen, with the aid of a pair of tentacles around her mouth. She then searches for a Joshua tree flower in which to lay her eggs, smelling each flower with her antennae to ensure another female has not gotten there first. Too many eggs in one flower causes the flower to stop forming, thus starving the moth larvae.

Pollination

• Once the female yucca moth finds a pristine flower, she cuts a hole in it using a bladelike organ that comes out of her tail. She lays eggs in the flower's ovary then removes some of the pollen she's been carrying and applies it to the flower's stigma, pollinating the flower. When the pollinated flower bears fruit and seeds, the moth larva have food, and the Joshua tree propagates itself when the seeds fall and germinate to become new trees.

Growth

• Yucca moth larva require only a few weeks to reach full maturity. Once grown, the larva fall to the ground, burying themselves in the soil and forming a cocoon that remains shut until the following spring. When the Joshua tree flowers again in spring, the cycle begins anew. Sometimes weather conditions are poor enough to prevent the Joshua tree from blooming, but some yucca moth pupae remain dormant in the soil and emerge the following year, according to a U.S. Forest Service website article.

Culture

• The Joshua tree grows in sunny, arid conditions in U.S. Department of Agriculture plant hardiness zones 8 to 10. The tree is very drought-tolerant and requires exceptionally well-draining soil. It grows quite slowly, gaining only 2 to 3 inches annually and taking up to 60 years to reach maturity. A Joshua tree that never blooms grows straight upward like a stalk, producing no branches, according to the U.S. National Park Service's website.