Yucca: Overlooked star of early summer

COLUMBIA, Mo.—Those towering flower stalks covered with white, bell-shaped blossoms that appear in early June belong to yucca, a plant with a somewhat unfortunate name.

Yuccas are resilient and striking additions to water-wise landscapes, said University of Missouri Extension horticulturist David Trinklein. Beyond their tough exterior, they provide year-round evergreen texture and an abundance of flowers each spring that support local pollinators.

With their rigid, sword-like foliage and dramatic late-spring blooms, yuccas offer structural contrast that anchors softer, more traditional perennials. Yellow-variegated cultivars such as ‘Color Guard’ or ‘Bright Edge’ add a year-round splash of color to the landscape. Yuccas are an extremely low-maintenance, drought-tolerant choice for modern, sustainable garden designs, Trinklein said.

Botanists have debated the classification of yucca plants for many years. Early descriptions in the eastern United States suggested there were two separate species: Yucca filamentosa and Yucca smalliana. Some experts agree, while others see them as variations of the same plant. Today, Yucca filamentosa is the name most commonly used to refer to this plant.

Each year, in late spring or early summer, a single flower stalk, looking somewhat like a giant asparagus spear, arises from the center of yucca’s rosette of leaves. Creamy-white, nodding flowers adorn each stalk in large clusters atop the towering stalks. Although yucca’s foliage rarely grows more than 3 feet high, flower stalks typically reach 5-8 feet in height.

These soaring flower stalks are often the plant’s most attention-getting attribute, seemingly coming out of nowhere from the shorter leaves and creating a nice contrast with the foliage. The evergreen character of its leaves is another feature that makes yucca an attractive choice.

Yucca has been described as either a perennial or a shrub. It is native to the southeastern U.S. and Mexico, where it frequents dry, sandy locations. Hardy through Zone 5, yucca is not native to the Midwest but has naturalized various locations throughout the area.

Yucca adapts to a wide range of conditions. However, it prefers drier sites and full sun, although it will tolerate some shade. Poorly drained soil is perhaps its only weakness. This plant develops a very deep and tough tap root, a feature that makes it widely adaptable but also presents a problem when removing established plantings.

Yucca flowers attract butterflies and other pollinators. However, their most remarkable relationship is with the yucca moth (Tegeticula yuccasella). Caterpillars of this moth feed exclusively on seeds of yucca, and adults are exclusive pollinators of this plant. The adult moths are short-lived and do not feed during their lifetime. For that reason, they lack the typical long tongue (proboscis) of most moth and butterfly species, instead sporting specialized tentacles in its place. The moths use these tentacles to scrape pollen from the anthers of flowers and deposit it on the stigma of a different flower.

The yucca plant and the yucca moth share an obligate mutualistic relationship. The plant depends entirely on the moth for pollination, while the moth’s larvae survive exclusively by eating the developing yucca seeds.

Yucca often is overlooked as a landscape plant because many consider it commonplace. This is unfortunate, since its striking spires of evergreen foliage and dramatic summer blooms provide year-round beauty with minimal maintenance.

Photo

Yucca filamentosa. Photo by H. Zell. Shared under a Creative Commons license (CC BY-SA 3.0).