It is an herbaceous annual plant, which grows weakly erect and scrambling, with stalks about 10 to 50 cm long. Its pink 7 to 9 mm flowers appear from April to October in the northern hemisphere. They are two lipped and spurred, with sepals running a quarter the length of the petals. The fruit is an achene. It contains alkaloids, potassium salts, and tannins. It is also a major source of fumaric acid.