Short Description
Usnea, commonly called Old Man’s Beard, festoons the trees of undisturbed forests with its tangle of pale green threads. This fruticose (shrubby) lichen hangs in trailing tufts several inches long, often from twigs and bark in the lower canopy. Soft and elastic, it sways with the slightest breeze, giving old woods a mystical, bearded appearance. Where you find Usnea in abundance, you can bet the air is clean – this lichen is extremely sensitive to pollution and flourishes only in healthy environments. Beyond its ecological role as an indicator, Old Man’s Beard has a storied past in folk medicine: long ago it was gathered as an antiseptic bandage and remedy for coughs due to its potent anti-microbial compounds. In the forest, though, it simply lives quietly on bark, absorbing moisture from fog and rain and getting nutrients from the air. Its presence lends an ancient character to the woods, as if the trees themselves grew beards over time.
TYPE
Lichen
ELEVATION
0–4,000 ft (found from lowlands to mountain forests wherever suitable moisture and host trees occur)
HABITAT
Hanging from the branches and trunks of trees in moist, cool forests; especially abundant on older or dead trees in areas with clean, humid air
BLOOM / SEASON
Non-flowering (lichen; propagates via fragmentation and tiny powdery soredia year-round)
LEAF & STEM
A fruticose lichen that forms tufted, dangling masses of fine, branching filaments. Each "strand" of Usnea is a thallus consisting of a tough, thin outer layer that is pale yellow-green (thanks to symbiotic algae) and a central core of white, elastic fibers. This inner core is unique – if you gently pull a strand, the outer cortex will break but a stretchy white thread inside is revealed, a key ID feature of the genus. The branches are irregularly forked, often with tiny side branchlets, and may carry small, powdery soredia on their surface (these are reproductive granules that can rub off to start new lichens). Old Man’s Beard typically has no large fruiting bodies visible to the naked eye; occasionally it produces minute reddish or pale disk-like apothecia on the tips of branches, but reproduction is mainly by pieces breaking off and dispersing. The texture is slightly coarse to the touch (not slimy or smooth). Color ranges from light green to gray-green, and unlike Spanish moss (a flowering plant it’s sometimes mistaken for in appearance), this lichen’s strands are relatively short in northern climates (a few inches long, not feet). It lacks leaves or obvious structures other than the branching, hair-like thallus.
SIMILAR SPECIES
Several other tree-dwelling lichens hang from branches, but Usnea’s combination of pale green coloration and an elastic central cord sets it apart. *Witch’s Hair Lichen* (*Alectoria sarmentosa*), for example, is also stringy and hangs from trees in moist forests, but it tends to be more yellowish chartreuse in color and does not have the white stretchy core (its strands snap more cleanly). *Horsehair Lichen* (*Bryoria* species) drapes from trees in long tresses too, but those are dark brown to black in color, resembling tail hair. Green "stringy" lichens like *Ramalina* or *Evernia* are usually shorter and flatter in form (and Evernia, or Oakmoss, has a different, branching-flat appearance). One could also confuse Old Man’s Beard with Spanish Moss at a glance, but Spanish Moss is a flowering plant of warmer climates and isn’t found in New England forests. In short, if you see gently dangling, light green lichen strands on a northern forest tree and they stretch when pulled, you’re looking at an Usnea.
ECOLOGY
A long-lived, slow-growing epiphyte that hangs from spruce and fir branches, intercepting cloud moisture and fog and releasing it drip-by-drip to the understory. The wiry thalli host diverse micro-fauna and are used by songbirds as nest lining and camouflage. Highly sensitive to air pollution and chronic drying, so robust tufts indicate clean, humid air. When storms shed branches, the fallen lichens decompose and contribute trace nutrients to otherwise nutrient-poor forest floors.
STATUS
Old Man’s Beard lichens are not rare globally – there are many Usnea species found in forests around the world – but they are very sensitive to environmental conditions. In regions with severe air pollution or heavy deforestation, they decline or disappear, which historically happened in parts of Europe (where some Usnea are now protected). In the White Mountains and broader New Hampshire woodlands, Usnea is still relatively common in clean, damp areas and has no legal protection status. Its abundance in an area is a good sign of air quality and forest continuity. Because it relies on mature trees and takes time to grow, it can suffer when old forests are logged. Generally, however, as long as large tracts of forest remain and the air stays unpolluted, this lichen will continue to grace the trees. It’s a resilient survivor of pristine habitats – a natural air filter and a silent witness to the purity of its surroundings.
Field Notes
- A fruticose lichen that forms tufted, dangling masses of fine, branching filaments. Each "strand" of Usnea is a thallus consisting of a tough, thin outer layer that is pale yellow-green (thanks to symbiotic algae) and a central core of white, elastic fibers. This inner core is unique – if you gently pull a strand, the outer cortex will break but a stretchy white thread inside is revealed, a key ID feature of the genus. The branches are irregularly forked, often with tiny side branchlets, and may carry small, powdery soredia on their surface (these are reproductive granules that can rub off to start new lichens). Old Man’s Beard typically has no large fruiting bodies visible to the naked eye; occasionally it produces minute reddish or pale disk-like apothecia on the tips of branches, but reproduction is mainly by pieces breaking off and dispersing. The texture is slightly coarse to the touch (not slimy or smooth). Color ranges from light green to gray-green, and unlike Spanish moss (a flowering plant it’s sometimes mistaken for in appearance), this lichen’s strands are relatively short in northern climates (a few inches long, not feet). It lacks leaves or obvious structures other than the branching, hair-like thallus.
- A long-lived, slow-growing epiphyte that hangs from spruce and fir branches, intercepting cloud moisture and fog and releasing it drip-by-drip to the understory. The wiry thalli host diverse micro-fauna and are used by songbirds as nest lining and camouflage. Highly sensitive to air pollution and chronic drying, so robust tufts indicate clean, humid air. When storms shed branches, the fallen lichens decompose and contribute trace nutrients to otherwise nutrient-poor forest floors.
- Old Man’s Beard lichens are not rare globally – there are many Usnea species found in forests around the world – but they are very sensitive to environmental conditions. In regions with severe air pollution or heavy deforestation, they decline or disappear, which historically happened in parts of Europe (where some Usnea are now protected). In the White Mountains and broader New Hampshire woodlands, Usnea is still relatively common in clean, damp areas and has no legal protection status. Its abundance in an area is a good sign of air quality and forest continuity. Because it relies on mature trees and takes time to grow, it can suffer when old forests are logged. Generally, however, as long as large tracts of forest remain and the air stays unpolluted, this lichen will continue to grace the trees. It’s a resilient survivor of pristine habitats – a natural air filter and a silent witness to the purity of its surroundings.
Photo Credits
(c) Nathan Sobol / NH48pics.com