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Collin County Chapter

From Green to Gold: Exploring the Adaptable Western Soapberry

In our North Texas environs, there is an often overlooked and underappreciated tree — the Western Soapberry (Sapindus saponaria var. drummondii). Despite its modest presence, this native North Texas tree holds many virtues that warrant more attention from native plant devotees.

Photo courtesy of Lady Bird Johnson Wildflower Center

Thomas Drummond’s Work in Texas

The Western Soapberry is indigenous to the south-central and southwestern regions of the United States, including North Texas. Its botanical name, Sapindus saponaria var. drummondii, pays homage to Thomas Drummond, the renowned Scottish botanist who explored Texas and much of North America in the early 19th century. Drummond spent nearly two years in Texas, and his efforts led to the official classification of the Western Soapberry.

Soapberry Characteristics

Flourishing in various habitats, from riparian zones to upland forests, this deciduous and dioecious tree typically reaches heights of 10 to 50 feet. Western Soapberry thrives in diverse habitats – tolerating drought, poor soil, and air pollution, making it an excellent match for challenging landscapes. With a single stem and low branches, it forms a round crown that transitions from vibrant green in spring and summer to golden hues in the fall.

Soapberries produce translucent yellowish-green fruits about ½ inches wide and resemble grapes. The fruit matures in the fall and often lingers through winter. A fleshy shell surrounds the dark-colored seed, encased in a saponin-rich sac. When soaked in water, this sac lathers, creating a natural soap substitute – the quality that earned the tree its common name. Below is more on the distinctive features of the tree:

  • Elegant Foliage: The tree’s compound leaves reach up to 18 inches in length. Each leaf features numerous paired leaflets with a glossy sheen.
  • Flowers – Large, cream-colored clusters up to 10 inches long and 6 inches wide appear in May and early June.
  • Sculpted Bark:  In the winter, the tree’s bark develops a textured, grayish appearance, adding a sculptural element to the landscape.

Vital Part of Our Ecosystems

The Soapberry plays a significant role in our local ecosystems. With an extensive root system, the tree aids in erosion control along waterways, stabilizing soil and preventing sedimentation. Other benefits to ecosystems include:

Photo courtesy of Lady Bird Johnson Wildflower Center
  • Prolific Pollinator: The fragrant flowers act as a magnet for a variety of pollinators.
  • Soil Enrichment: Its ability to fix nitrogen in the soil enriches the surrounding environment and benefits neighboring plants.
  • Wildlife Haven: The tree’s dense foliage protects nesting birds and small mammals. Additionally, the fruits attract a variety of wildlife, which helps disperse the seeds.

Biological Partnership

The Western Soapberry and the Soapberry Hairstreak butterfly (Hemiargus amymone) have a fascinating symbiotic relationship. Western Soapberry produces a mild toxin that deters most predators. However, the Soapberry Hairstreak caterpillar has evolved to tolerate this toxin, making it the only herbivore known to feed on the leaves without harm. As a result, their caterpillars’ sole food source is the Western Soapberry. This partnership helps ensure the continuation of the Soapberry’s pollinator by providing a haven for its young.

Landscaping with the Western Soapberry

Beyond its ecological contributions, the Western Soapberry offers numerous benefits to homeowners. It is well suited for suburban and urban settings with its tolerance for poor soil and disturbed sites. Providing ornamental value, shade, and adaptability in urban environments, it enhances parks, gardens, and residential areas. Plus, its shape makes it very wind-resistant.

Photo courtesy of Lady Bird Johnson Wildflower Center

One drawback of the tree is finding the species at nurseries. They are occasionally available, but more often, they can be found at native plant sales. Here are some tips for incorporating it into your landscape:

  • Location: Choose an area with full sun to partial shade and well-draining soil.
  • Water: While drought tolerant, newly planted Western Soapberry trees benefit from regular watering during their first year or two, especially during extended dry periods. Once established, supplemental watering is rarely necessary.
  • Maintenance: Requires minimal maintenance. As with all trees, occasional pruning to remove dead or diseased branches can help maintain their desired shape and promote healthy growth.
  • Fruit Toxicity: Be aware that the Western Soapberry fruits are toxic to humans and pets.

The Soapberry Imposter

A word of warning: the invasive and fast-growing Chinaberry tree resembles the Western Soapberry. In fact, one of the lesser-used common names for Sapindus saponaria var. Drummondii is “Wild Chinaberry”. Some distinguishing characteristics are that the Chinaberry’s leaves are narrower and have more pointed edges, and during the winter, the Soapberry fruit is translucent, while the Chinaberry is opaque.

In conclusion, the underappreciated Western Soapberry offers adaptability, ecological vitality, and beauty to North Texas’ cultivated and wild spaces. So, when planning future additions to your home landscape, consider this unsung native tree.

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