Mercurialis annua is a common annual herb found all over Europe, Asia, and North Africa. It has many common names, such as annual mercury, English mercury, and dog's mercury. Other synonyms for this plant include Mercurialis perennis, Mercurialis heterophylla, and Mercurialis intermedia. The plant is often found growing in damp places, such as woodland edges, hedgerows, and streamsides. Some people mistake it for other plants, like sweet woodruff or chickweed. The plant has been used for medicinal purposes for centuries, although it is now largely considered toxic. Despite its toxicity, it is important to recognize the plant and know its many synonyms if you encounter it in the wild.