Dolichousnea longissima, Old Man's Beard or Methuselah's Beard Lichen, is a lichen in the family Parmeliaceae

Parmeliaceae

The Parmeliaceae is a large and diverse family of Lecanoromycetes. With over 2000 species in roughly 87 genera, it is currently regarded as the largest family of lichen forming fungi...

. It was previously known as Usnea longissima.

Distribution

D. longissima is found in boreal forests and coastal woodland in Europe, Asia, and North America.

Description

This lichen is fruticose, with very long stems and short, even side branches. It is considered the longest lichen in the world. The stems are usually 15 to 30 cm in length but are sometimes much longer.

Ecology

The most frequent host of this lichen is spruce trees. It is currently on threatened status.