Lichens are organisms formed by the interaction of a fungus species and another organism usually algae. The String of Sausages Lichen, also known as Old Man’s  Beard, are pale grey-green and some produce striking disc-like fruit bodies. They can be seen dripping from the barks and branches of upland oakwood found in the Dart Valley.

Lichens on trees play an important role in the eco system of woodlands. They provide valuable microhabitats, shelter and food for various small invertebrates. These are in turn prey for larger insects and birds.

The String of Sausages Lichen once could be found on trees throughout Britain but the impacts of past sulphur dioxide pollution and continued nitrogen air pollution has resulted in their loss. The presence of this lichen on Brimpts Farm is an indicator of exceptionally clean air.

Many String of Sausages Lichen contain usnic acid which is a potent antibacterial and antifungal agent. They have also been used historically for dyes and in some areas used as a fire starter when it is dry and crisp.