Horticulture Supervisor, Kyle Cheesborough
Soapweed (Yucca glauca), a plant native to Missouri which has a very intimate relationship with the yucca moth. Soapweed flowers emit a sweet smell at night to attract moths, but the only one that matters to the plant is the yucca moth. Yucca moths are small, insignificant, and all white. They choose the flowers of soapweed plants to mate. Upon mating, the female will visit the soapweed flower’s anthers (male organs) and collect pollen, using an unusual pair of tentacles near her mouth to scrape the pollen and store it under her chin.
She then searches for another flower that has yet to host any yucca moth eggs. Upon finding a vacant flower, the female yucca moth will lay her eggs, being careful not to lay too many, as the larvae will feed on the soapweed seeds. If too many larvae feed on the seeds, the plant will abort the developing fruit, something disadvantageous to both the moth and the plant. After laying her eggs, the female yucca moth visits the flower’s ovary, depositing her sticky pollen ball, thus pollinating the plant to ensure that seed will develop to provide food for her larvae. The relationship between soapweed yucca and the yucca moth is said to be an obligate mutualism, meaning that if one were to disappear, the other would soon follow.
Missouri primrose (Oenotheramissouriensis) is also a moth-pollinated plant. These flowers open in the very early morning hours, close during the day, and open again in the evening, staying open through most of the night. The flowers are very large, chartreuse-yellow, too large to be effectively pollinated by most bee species. Large moths like sphinx moth and hawk moth are required to pollinate these plants. Both hawk moths and sphinx moths can be seen in our area around mid-to-late summer, and a gardener can be almost guaranteed to see these moths around a flowering Missouri primrose.
Both soapweed and Missouri primrose can be found in the cemetery in planting beds at the intersection of Aspen Ave. and Ravine Ave.
In Wild Wood Valley you can find two types of wild false indigo (Baptisia), yellow false indigo (Baptisiasphaerocarpa) and a ‘Starlite Prairieblues’ false indigo (Baptisia x bicolor ‘Starlite’). These are pollinated by bumble bee species, the only bees large and strong enough to pry open the flowers, accessing the pollen and nectar within.
After pollination, the false indigo will develop distinctive, black seed pods about two inches long and one inch wide. Native Americans used these seed pods as baby rattles, as the seeds rattle freely inside the dried pod.
Compiled by Cara L. Crocker
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