This plant is a member of the lily family and there are 40 species native to the New World, most of which are found in our southwestern states. South Carolina is home to three species, and the one blooming near us now is Yucca filamentosa. Also known as Spanish Bayonet, yucca has lance shaped leaves that end in sharp points. Native Americans used this plant for food ( flowers ), medicine ( leaf tea ), utensils ( leaf baskets ), and cleansing ( root extract as a soap ).

In the spring it produces a tall stalk with many drooping white flowers. Flowers open fully at night and emit their fragrance that attracts the yucca moth. Each species of yucca has its own pollinating moth species, and their relationship is a classic example of a type of symbiosis called mutualism. Plant and moth depend on each other for reproduction and both benefit from the relationship. The blossom close-up shows both male and female moths resting on the male structures ( stamens ) of the flower. The female moth emits a "fragrance" of her own to attract a mate. Such attractants, effective in extremely small amounts, are called "pheromones." After mating, the male's work is over, but the female's tasks have just begun. First she gathers pollen from the flower's anthers. She has special mouth parts to package pollen and carry it to the flower's female part ( pistil ), where she deliberately pushes it into its tip called the stigma. This is one of very few cases where pollination by an insect is not just a chance brushing of pollen on the right place. After pollinating the moth lays her eggs in the ovary of the pistil which develops into the fruit, containing seeds.

When moth eggs hatch, larvae feed upon the seeds, and are protected inside yucca fruit. Mature moth larvae eventually leave fruits and turn into pupae which hatch into moths the next blooming season. It's crucial, of course, that not all seeds be consumed by moth larvae, otherwise the plant's reproductive potential is reduced rather than enhanced by its moth partner. So what happens is this: Moths somehow "know" not to "put all their eggs in one pistil"! Yuccas routinely drop a number of flowers, including some that have been pollinated. Moths who lay a few eggs in several pistils will assure their reproduction. Cool! It's a classic example of what biologists call "co-evolution." Over time these two species have developed a system of mutual interdependence. Moths which lay appropriate numbers of eggs continue to be naturally selected by their host plants! What a wondrous example of God's creations, interacting through the ages! Not so "yucky"!

Yucca moths were discovered and recorded by entomologist Charles Valentine Riley in 1876, and their biology and that of yuccas is still under investigation. Questions have been answered, but many remain to be investigated. This week, entomologist, Dr. Glenn Svensson from Lund University, Sweden, visited Due West to study a population of yuccas blooming out Mt. Lebanon Road on family property of Mrs. Vivian Stackhouse and Mrs. Mary Williams. As a postdoctoral associate at the University of South Carolina, Dr. Svensson is performing chemical analyses of fragrances produced by different populations of yucca. The photo below shows some of the apparatus used to obtain fragrance samples. I took Dr. Svensson and his student assistant, Michael Hickman to the Yucca patch at 7:30 p.m., and they set up sample apparatus on 11 flowering plants. They put oven bags over the tops of blooming stalks to concentrate fragrance chemicals. A sample tube was inserted through a hole in the bag, and connected to a small battery powered pump. Pumps were turned on and run until midnight, when we returned, equipped with special head lamps, to dismantle the apparatus and return sample tubes to our freezer. They will be analyzed in the lab at USC. Dr. Svensson has sampled yucca populations in Florida, Georgia and North Carolina, and he will be traveling to Idaho later in the summer to conduct investigations there.

Yucca fragrance is described as "soapy". To me, flowers seem to have a mild citrus-like odor.