Flora Fact: Twister
Twistleaf yucca cleverly twirls up rain-catching leaves.
By Dyanne Fry Cortez
Traveling through Central Texas in May, I’m often enchanted by the graceful white blooms of twistleaf yucca.
Like me, Yucca rupicola is a Hill Country native. Several types of yucca grow in my part of the state, but this species is found nowhere else. It’s endemic to the Edwards Plateau, clinging to rocky ridges, dotting grasslands and pastures, and nestling in the partial shade of open woods.
Twistleaf yucca is easily identified by the twisting of its long, narrow, bright-green leaves. Leaf edges are lined with tiny yellow (to light brown) saw teeth, with a sharp spine at the tip of the leaf. The spiral leaf cluster, called a rosette, hugs the ground, measuring a foot or two across. New leaves emerge at the center, straight at first but twisting as they age. Botanists suspect it’s an adaptation to collect rainwater and funnel it to the growing center of the plant.
Y. rupicola is typically seen scattered across a landscape, appearing as a solitary plant or in small, open colonies. It grows in community with other native shrubs, grasses and trees, mixed into a palette of browns and muted greens. When the flowers open in late spring, however, this plant stands out.
“Lantern-like” is how Craig Hensley describes them. Hensley is an interpreter at Guadalupe River State Park, which has a nice population of twistleaf yucca outside its Discovery Center. A plant produces a single bloom stalk, 2 to 5 feet tall. The cream-colored flowers, sometimes tinged with palest green, dangle from a loosely branched panicle at the top.
Individual blossoms, viewed at close range, are around 2 inches long with six tepals (three white petals and three white sepals) and six stamens surrounding a central pistil. The reproductive organs are arranged in such a way that the plant can’t fertilize itself. All yuccas depend on certain species of yucca moths to carry pollen from one blossom to the next. The moths, in turn, rely on yucca flowers to provide the nursery for their offspring. When that mutual-benefit arrangement proceeds as planned, twistleaf yucca will produce small black seeds in a woody capsule. When it doesn’t, the plant can and does reproduce by vegetative means. The short stem may branch just under the soil surface, sending up shoots that develop into new leaf clusters.
Deer love to nibble on the fresh flowers. They usually don’t bother the well-armed leaves, but it’s easy enough to step around the spines and reach the blooms, which tend to be just the right height for grazing. Humans can eat yucca flowers, too.
“I can’t describe the taste, but it is certainly unique,” says Hensley.
Other good places to see twistleaf yucca include the trails at Hill Country State Natural Area, the prairies at LBJ State Park or almost any roadside in the Edwards Plateau region. They live here year-round, but the best time to go scouting is mid- to late May. When you round a bend and find one in bloom, it’s always a nice surprise.
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Common Names: Twistleaf yucca, twisted-leaf yucca, Texas yucca Scientific Name: Yucca rupicola Size: Foliage grows up to 2 feet tall; bloom stalks rise up to 5 feet. Did You Know? Rupicola means "lover of rock." |
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