[1] It is native to Europe but it is present elsewhere as a weedy introduced species.

[2][3] This is a perennial herb growing anywhere from 20 centimetres to about half a metre in height.

[2] The leaves are long and very narrow on most of the plant, with more oval-shaped leaves toward the tips of the stems.

[2] At the ends of the branches are inflorescences of tiny flowers.

[citation needed] The fruit is a spherical capsule about half a centimetre wide containing tiny gray seeds.