Earth Notes: Blooming Yuccas
The magnificent white-lily like flowers of the many Yucca plant species only grace us in the spring when the stars align. Yucca blooms often occur in alternating years depending on rainfall, temperature, and climate.
Yuccas have a unique pollination regime. They are considered “mutualist obligates,” meaning every species of yucca requires a specialized yucca moth to carry out pollination—with the exception of the Joshua tree, which has two. Thus the fate of the two species, plant and insect, are intertwined.
The delicate balance between them exemplifies symbiosis at its finest. The yucca moths mate within the protection of the yucca flower and females lay their eggs within the flower’s ovary.
In exchange for the room and board of her future larvae the female moth transfers pollen from one flower to another. That enables the production of future fruit, the seeds of which will feed the moth’s young.
After the moths have deposited enough eggs into a flower’s ovary they leave a scent marker letting other moths know the space is taken and the flower can’t handle any more guests. The developing larvae eat the seeds from the maturing yucca fruit, never eating more than one third of what is available, which assures the plant’s ability to persist.
That’s why a yucca blooming is a miracle of nature.