Mercurialis

Mercurialis is a genus of annual and perennial herbaceous plants in the family Euphorbiaceae. The genus is native to Europe, North Africa, and Western Asia. The common name for plants in this genus is mercury.

There are about 15 species of Mercurialis. The most well-known species is Mercurialis annua, also known as annual mercury. This is a common weed found in disturbed soils, gardens, and waste areas. It is an erect, branching plant that can grow up to 60 cm tall. Mercurialis annua has opposite, toothed leaves and small, inconspicuous flowers that are dioecious, meaning that individual plants are either male or female. The fruit is a spiny capsule.

Another notable species is Mercurialis perennis, or perennial mercury. This species is found in woodlands and shady areas. It is a rhizomatous perennial with broader, ovate leaves. Like Mercurialis annua, it has dioecious flowers. All parts of Mercurialis plants are considered toxic if ingested, particularly to livestock, and can cause gastrointestinal upset and other symptoms. Contact with the sap can also cause skin irritation in some individuals. Historically, some species were used in folk medicine for various ailments, but these uses are not scientifically supported and carry risks due to the plant's toxicity.