Carolina Buckthorn (Frangula caroliniana) is a native North American plant often confused with invasive, toxic buckthorn species. This confusion arises from its common name, historical uses, and close relation to harmful relatives. This guide clarifies the plant’s edibility status, focusing on accurate identification and the chemical components that determine its safety.
Key Features for Identification
Carolina Buckthorn is a deciduous shrub or small tree, typically reaching 12 to 20 feet tall, characterized by an open, slender-branched crown. A primary distinguishing feature is the complete absence of thorns, despite the plant’s common name. This lack of thorns helps separate it from more dangerous relatives. The bark is generally smooth and gray-brown, often marked with small, horizontally elongated lenticels.
The simple leaves are arranged alternately along the stems, measuring two to six inches long. They have a glossy, dark-green surface with notably straight and parallel veins. Leaf margins are either smooth or feature very small, rounded teeth, and the leaves maintain their green color well into late autumn.
Small, inconspicuous, yellowish-green flowers appear in clusters at the base of the leaves in late spring or early summer. These develop into small, berry-like fruits (drupes), approximately one-quarter inch in diameter. The fruit displays a distinctive color transition, starting bright green, turning red, and finally ripening to a deep, glossy black in the fall.
Edibility and Toxicity Status
The edibility of Carolina Buckthorn is complex due to anthraquinones, compounds present in various parts of the plant. These compounds act as strong laxatives or purgatives when ingested. The highest concentration of these active chemicals is found in the bark, the seeds, and the unripe green fruit.
The flesh of the fully ripe, black fruit is sometimes described as sweet and palatable, and it has historically been used by some Native American groups. However, even ripe fruit contains lower concentrations of anthraquinones, which can still induce a powerful cathartic effect. Therefore, the plant is generally categorized as mildly toxic and should be avoided or consumed only with extreme caution.
Consuming the seeds or unripe fruit dramatically increases the anthraquinone dosage, leading to severe gastrointestinal distress, including vomiting and intense diarrhea. The bark was traditionally boiled into a tea and used as a strong laxative due to its high concentration of these compounds. While birds consume the ripe fruit readily, humans should avoid all other parts of the plant, including the seeds inside the fruit.
Distinguishing Carolina Buckthorn from Toxic Look-Alikes
The greatest risk associated with Carolina Buckthorn is misidentification with highly invasive and toxic species, notably Common Buckthorn (Rhamnus cathartica). Frangula caroliniana has an alternate leaf arrangement and completely lacks true thorns. Common Buckthorn, by contrast, typically displays sub-opposite or opposite leaf arrangements, and its twigs often terminate in a sharp, spine-like thorn.
Leaf margins also differ significantly between the species. Carolina Buckthorn leaves are nearly smooth, while Common Buckthorn leaves are finely toothed along the edges. Additionally, the inner bark of the invasive Common Buckthorn is a vibrant yellow color, which is not characteristic of the native Carolina species.
Another look-alike is Glossy Buckthorn (Frangula alnus), which also lacks thorns and has alternate leaves. However, Glossy Buckthorn leaves are generally darker and shinier, often having noticeably curved, parallel veins. Frangula caroliniana leaves have a slightly less glossy appearance with more prominent, straight veins. Accurate identification requires combining features like leaf arrangement, margin texture, and the absence of thorns.