This is a herbaceous perennial that twines around other plants, in a counter-clockwise direction. The pale matte-green leaves are arranged spirally, simple, pointed at the tip and heart or arrowhead-shaped at base.

Flowers are produced from late spring to the end of summer. In bud, they are covered by large modified leaves called bracts. The open flowers are trumpet-shaped, 3-7 cm diameter, white, or pale pink with white stripes. Pollinating insects are usually hoverflies and moths. After flowering the fruit develops as an almost spherical capsule 1 cm diameter containing two to four large, black seeds that are shaped like quartered oranges. The seeds disperse and thrive in fields, borders, roadsides and open woods.

Its self-seeding (seeds can remain viable as long as 30 years) and the success of its creeping roots (they can be as long as 3-4 m) cause it to be a persistent weed and have led to its classification as a noxious weed.

This is a parasistic plant that posesses neither leaves nor roots. The young seedling attaches itself to its host plant immediately after germination by means of penetrating growths called haustoria and through these all the nutrients for further growth are absorbed from the host. It has no need of chlorophyll, hence no leaves, and no need to obtain its own water and minerals, hence no roots. Its thin stems wind around the stems of the host, growing at the tips and dying off further back, so it literally progresses through the host vegetation. The mass of thin stems is more noticable than the small pale flowers, hence its common name, Witches’ Hair/Teufelszwirn

Hosts vary greatly and include nettles, clovers, lucerne, daisies, hops, bedstraw and many other wayside plants.

The clusters of rather small and insignificant flowers produce seed capsules that remain attached to the withered flower which acts as a balloon to aid distribution by wind. Otherwise distribution is mainly accidental, by trampling, foraging or catching on fur of passing animals.