Yuccas (Spanish Bayonet; Soapweed)

Yucca smalliana, Y. glauca, and Y. arkansana

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Photo of soapweed, a type of yucca
Soapweed (Yucca glauca) is one of two yuccas native to Missouri. It’s found only in the northwestern corner of the state and is uncommon.
Howard F. Schwartz, Colorado State University, Bugwood.org
Thorny
Other Common Name
Adam’s Needle
Family

Agavaceae (agaves)

Description

You can find three species of yucca growing wild in Missouri. Spanish bayonet was introduced from the Southwest and has escaped from cultivation, but our two yuccas, both called soapweeds, are native.

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. Leaves are basal, stiff, narrow, sharply pointed, to 2½ feet long, often with fibrous edges. Fruit is a large, papery capsule with hundreds of flat, black seeds.

Soapweed (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, Y. 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.

Size

Height: to about 7 feet (flowering stalk).

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Photo of Spanish bayonet flowers.
Spanish Bayonet (Adam’s Needle) (Flowers)
Spanish bayonet is common in Missouri, occurring on roadsides, railroads, abandoned homes, and gardens.

spanish_bayonet_leaf_filaments_7-11-14.jpg

Photo of Spanish bayonet base showing filaments curling from leaf margins.
Spanish Bayonet (Adam’s Needle) (Leaves)
The leaves of Spanish bayonet are stiff and swordlike, hence the common name. Note how fibers split and curl away from the leaf margins.

spanish_bayonet_dried_fruits_7-11-14.jpg

Photo of Spanish bayonet dried fruit capsules.
Spanish Bayonet (Adam’s Needle) (Dried Fruit Capsules)
The fruit of Spanish bayonet is a large, papery capsule with hundreds of flat, black seeds.

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Photo of Spanish bayonet basal leaves.
Spanish Bayonet (Adam’s Needle) (Leaves)
Spanish bayonet is scattered statewide. It was introduced to Missouri from the Southwest.

spanish_bayonet_green_fruits_7-11-14.jpg

Photo of Spanish bayonet green fruit capsule.
Spanish Bayonet (Adam’s Needle) (Green Fruit Capsules)
A certain type of moth fertilizes yuccas, while she deposits her eggs into the flower’s ovary. The growing caterpillars eat only some of the seeds.

Soapweed_Yucca_glauca.jpg

Illustration of a soapweed plant, flowers, and fruit
Soapweed
Soapweed, Yucca glauca

Spanish_Bayonet_Yucca_smalliana.jpg

Illustration of Spanish bayonet plant, flowers, fruit
Spanish Bayonet (Adam's Needle)
Spanish bayonet, Yucca smalliana
Habitat and conservation

Spanish bayonet occurs on roadsides, railroads, abandoned homes, and gardens. 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, and Y. glauca is uncommon, for it is restricted to the few remaining loess hill prairies in the state.

image of Yuccas Spanish Bayonet Soapweed Adams Needle Distribution Map
Distribution in Missouri

Spanish bayonet is scattered statewide. Our two native soapweed yuccas are restricted to northwestern counties (Y. glauca) and to southern counties (Y. arkansana).

Human connections

Yuccas are tremendously useful. 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. Today, yuccas are valued by landscapers.

Ecosystem connections

Only a certain type of moth can fertilize yuccas, which occurs as the female moth deposits eggs into the flower’s ovary. The growing caterpillars eat some, but not all, of the plant's seeds. A Missouri entomologist, Charles V. Riley, discovered this trade-off between plant and insect.