Greenbrier Vines are typically dismissed as a nuisance due to their abundant thorns and aggressive growth. But these native plants are the very definition of “Texas-tough”, as the woody vine can thrive in a range of habitats and conditions. In suburban landscapes, they will not win any popularity contests. But they play a vital role in supporting wildlife, stabilizing soils, and enriching our North Texas ecosystems.
Like many native plants and animals, we often view their characteristics through a narrow lens without considering the roles that plants like Greenbrier Vines play in our ecosystems.
Greenbrier Vines: Hardy, Thorny, and Adaptable
The two most common Greenbrier Vines in North Texas are – Smilax rotundifolia, typically called Roundleaf or Common Greenbrier, and Smilax bona-nox, known as Saw Greenbrier or Sawbriar.
These woody vines are characterized by rounded, leathery leaves and stout, sharp thorns. Both species prefer warm-temperate climates, but Rotundifolia has a broader range extending from the eastern half of Texas through much of the eastern U.S. to southern New England. Bona-nox is limited to the southeastern and south-central states.
They thrive in a variety of habitats, from bottomland hardwood forests to upland thickets, and especially, disturbed areas. It is well adapted to fluctuating conditions, tolerating drought, flooding, and a range of soil types. Greenbrier is most often found in semi-shade to full sun conditions. They are evergreen to partially deciduous and perennial. We most often observe it as a climbing vine, but it can also form a small, tangled bush. Under the right conditions, the vines can form dense thickets, creating impenetrable barriers in the understory.
They have a persistent woody rhizome, often forming large, knotty tubers over time that send up new shoots, making it difficult to eradicate once established. The stems are typically green and have an intense climbing or sprawling habit, using tendrils to grip onto nearby vegetation. The plant produces clusters of small greenish flowers, which give way to dark, bluish-black berries in the fall.
Rotundifolia vs. Bona-Nox: What Sets them Apart
While the two Greenbrier species share many similar traits, there are some distinguishing characteristics:
- Leaf Shape and Texture: Rotundifolia typically has rounded to heart-shaped leaves with smooth or slightly irregular margins. Bona-nox has a broader range of leaf shapes, often with deep lobes or irregular margins, and spiny or bristly projections.
- Leaf Appearance: Bona-nox often has a mottled or blotchy green appearance compared to Rotundifolia’s deep green color.
- Stems and Thorns: The thorns of Bona-nox are more irregularly spaced along the stems and typically more aggressively armed. The stems have stout, flattened prickles, providing the common name of “Saw” Greenbrier, particularly on older or lower stem sections. Rotundifolia generally has a more uniform pattern of small, stout, hooked thorns.
- Growth Habit: Rotundifolia tends to form more dense, nearly impenetrable thickets, whereas Bona-nox can be somewhat less aggressive in its climbing and spreading.
- Preferred Habitat: Rotundifolia prefers moist forests, woodland edges, and thickets, while Bona-nox is more adaptable to dry, rocky, or sandy soils, including prairies and open woodlands.
Wildlife Loves This Thorny Vine
Thanks to its robust root system, Greenbrier helps stabilize the soil, prevents erosion, and plays a key role in forest regeneration. By anchoring disturbed soils and sending up new shoots, they help to quickly colonize disturbed areas and create protective cover for emerging plants.
Additionally, they are a crucial resource for wildlife, with their leaves providing food for deer and other herbivores. Plus, their thick tangles offer excellent nesting sites and shelter for birds and small mammals. The thickets created by Greenbrier also contribute structurally to creating ideal habitats for birds to nest and roost safely hidden within the thorny vines.
Numerous birds and animals eat the fruits, an especially important late fall and winter food for birds. Lastly, their modest spring flowers produce nectar and pollen for small bees and flies.
Reframing the Role of Greenbrier
Though typically viewed as a nuisance due to their thorny nature and aggressive growth, Smilax rotundifolia and Smilax bona-nox are integral components of North Texas’ ecosystems. These resilient vines support wildlife, help prevent soil erosion, and promote the regeneration of disturbed areas. Increasing our understanding of often-overlooked “nuisance” native plants, such as Greenbrier, allows us to better appreciate the essential roles they play within our North Texas ecosystems.
