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Answer: Chewing releases protoanemonin, causing burning of mouth and mucous membranes, salivation, abdominal pain and cramping, nausea, and vomiting.

Description

The plant consists of woody vines six to 18 feet long that climb by twining. It has big, bold flowers composed of striking septals of various colors surrounding a central basket of stamens and pistils. It grows throughout North America. Clematis species have attractive, complex flowers that are usually single and spaced out across the plant’s length, but some varieties have clustered blooms. The deep-green leaflets are arranged opposite, at intervals along the central vine (as seen in the accompanying photograph).

Toxins

Clematis and other plants in the buttercup family contain the compound ranunculin. Ranunculin is a glycosidic precursor that gets converted to the vesicant protoanemonin by enzymes released when the plant is chewed. This toxic compound is in highest concentration in the leaves and sap and can cause irritation and skin blistering. If eaten, it will cause burning of mouth and mucous membranes, salivation, abdominal pain and cramping, nausea, and vomiting. Hematuria and renal function effects have also been described.

Inadvertent exposure and exposure in animals is often self-limited by the oral symptoms.

Facts

• Although all flowers are made of modified leaves, the clematis has colorful septals, not petals. They are therefore “incomplete” flowers (a “complete” flower has four parts: septals, petals, stamens, and pistils). Septals are the outermost protective leaves for budding flowers. The lack of an internal set of colored leaves (petals) sets clematis (and hydrangeas) apart from most flowers.
• Clematis are also toxic to dogs, cats, and horses and can induce salivation, vomiting, and diarrhea.
• Protoanemonin has antimicrobial and fungicidal properties.
• A clematis leaf is compound and made up of the two opposite leaflets—each one is part of the “whole leaf.”