A tall erect herb. It grows 30-75 cm tall. It keeps growing each year from a woody rootstock. The stems are smooth and unbranched. The leaves are simple and opposite. They are long and narrow and without leaf stalks. The flowers are in groups of many flowers with equal length stalks. The flowers are greenish and 3-5 mm long. The fruit is a follicle and they occur in pairs. They are narrow and taper to a long slender beak.