Three species of yucca grow wild in Missouri. The most common one is Spanish bayonet, which was introduced from the Southwest and has escaped from cultivation. Our two native soapweeds are species of conservation concern.
- Spanish bayonet, or Adam’s needle (Yucca smalliana; formerly Y. filamentosa or Y. flaccida), has stout, scaly flower stalks topped by a panicle of many flowers, arising above a large basal cluster of stout, sharp-pointed, leathery leaves. The flowers are cuplike, with 3 sepals and 3 petals, 2 inches across, and creamy white. Blooms May–July. The leaves are basal, stiff, narrow, sharply pointed, to 2½ feet long, often with fibrous edges. The fruits are large, papery capsules with hundreds of flat, black seeds.
- Soapweed, or small soapweed yucca (Yucca glauca), is a native that, in Missouri, is found only in the northwestern corner of the state (Holt and Atchison counties). The base of the flowering portion of the flower clusters is not raised above the leaves, and the leaves are spine-tipped.
- Another soapweed, Arkansas yucca (Yucca arkansana), is a native that in our state is found only in the southern portion of Missouri’s Ozarks, along the Arkansas border. It is similar to Y. glauca, but it has softer leaves that are not spine-tipped.
Height: to about 7 feet (flowering stalk).
Spanish bayonet is scattered statewide. Our two native soapweed yuccas are restricted to northwestern counties (Y. glauca) and to southern counties (Y. arkansana).
Habitat and Conservation
Spanish bayonet occurs on roadsides, railroads, and abandoned homesites and is cultivated in yards and gardens. This is the yucca you are most likely to see. It is native to the southwestern United States, introduced here and escaped from cultivation.
Of our two native soapweeds, Y. arkansana is found in glades, open rocky woods, and roadsides in southern Missouri, and Y. glauca is uncommon and restricted to the few remaining loess hill prairies in the northwestern corner of the state.
Status
Missouri's most common yucca, Spanish bayonet (Y. smalliana), is not native to Missouri. It is native to the southwestern United States and was introduced to Missouri.
Our other two yuccas are native to Missouri, and they are both Missouri species of conservation concern, ranked as imperiled.
Human Connections
Wherever they grow, yuccas have a long history of being useful for people. The roots of some species have been used in soapmaking (thus the name "soapweed"), and the seeds have been eaten raw, roasted, or ground into a flour. The tough leaves provide fiber for cordage and broom-making. Yuccas have also been used medicinally. Today, yuccas are valued by landscapers.
In Mexico and elsewhere in Central America, yucca flowers are used in several tasty dishes.
Yuccas and agaves have been used by New World people in many ways throughout history, particularly in the Southwest. Ethnobotany is a fascinating and useful field of study, blending the study of plants with anthropology and history. By learning about the many ways people have cultivated and used plants across the world, we not only understand the intertwined history of plants and people but also get new ideas for developing plants in useful ways.
A Missouri entomologist, Charles V. Riley, discovered the amazing mutualistic relationship between yuccas and yucca moths. Only a certain type of moth can fertilize yuccas, which occurs as the female moth deposits eggs into the flower’s ovary. Without the cross-pollination effected by the moth, the yucca flowers generally cannot produce viable seeds.
- When he studied this remarkable plant-insect relationship in the 1870s, Riley was Missouri’s first official State Entomologist. The eminent St. Louis botanist George Engelmann had noticed that yuccas apparently need some kind of outside agent to accomplish pollination and suggested Riley look into it.
Ecosystem Connections
When yuccas are blooming, it’s time to look for yucca moths (Tegeticula spp.). Peek carefully into the yucca/soapweed flowers: the moths will be about the same color as the petals! The moths and their food plants are an amazing example of mutualism:
- The moth larvae, hatching from eggs laid in the pistil of the yucca flower, will eat some but not all of the yucca’s hundreds of developing seeds.
- The yucca can afford that price because the female moth possesses the specialized anatomy, and even special behaviors, to cross-fertilize the flowers as she deposits her eggs.
Yuccas are in the same group as agaves; the famous Joshua trees of the American Southwest are species Y. brevifolia. The state flower of New Mexico is the yucca. In the Southwest, many people are learning to landscape their yards using the many native, drought-tolerant species of yuccas and agaves; as with here, native landscaping helps expand habitat for native species. It also demands much less water and maintenance.
