Methuselah's Beard Lichen
Usnea longissima
Also called long beard lichen, old man's beard, usnea longissima
The longest lichen in the world, hanging in pale greenish ropes several metres long with short perpendicular side branches like a bottlebrush.
Overview
Methuselah's Beard Lichen (Usnea longissima, also placed in the segregate genus Dolichousnea) is a pendent fruticose lichen famous for producing the longest thalli of any lichen — individual strands regularly exceed a metre and exceptional specimens have been recorded at several metres, draping from conifer branches like pale rope.
It differs from typical beard lichens in its architecture. Instead of branching repeatedly and equally, it grows as a single dominant main cord that extends indefinitely, with short, roughly perpendicular side branches arranged along its length, giving a bottlebrush or feather-boa outline.
The species is closely tied to humid, cool, old-growth forest and has declined across much of its former range, making it one of the most widely used indicator lichens for forest continuity and clean air in both North America and Eurasia.
How to identify it
Thallus form
A single long, unbranched or sparsely branched main axis hangs vertically, commonly 30-200 cm and occasionally far longer. Along it, short lateral branches 1-5 cm long emerge at close to right angles at fairly regular intervals, producing a distinctly bottlebrush silhouette.
Cortex and central cord
The main axis lacks a continuous outer cortex — the surface flakes away in patches to expose the whitish medulla, giving a slightly scruffy, chalky, matte look. Inside runs the tough white elastic central cord typical of Usnea: pull a strand gently and it stretches slightly before the outer layers snap, leaving the cord intact.
Colour and texture
Colour is pale greenish-grey to yellowish-green or dull straw, paler and greyer than most beard lichens. The strands are soft and flexible when damp, becoming light and wiry when dry.
Reproductive features
Apothecia are very rare. Reproduction is essentially entirely vegetative, by soredia and by fragments of the main cord that break away and lodge on branches below.
Where and when it grows
This lichen hangs from the branches of conifers — spruce, fir, hemlock, Douglas fir, larch and pine — and occasionally from hardwoods, favouring the outer limbs of mature and veteran trees where air movement and light are good but humidity stays high. It concentrates in old-growth and long-unmanaged forest, cool humid valleys, riparian corridors, coastal rainforest and montane stands with frequent fog or cloud.
The distribution is broadly circumboreal — western North America from Alaska to northern California, parts of the northeastern United States and Canada, Scandinavia, the Baltic and Russia, and montane regions of eastern Asia — but populations have contracted sharply in managed and polluted landscapes. It is perennial, present year-round, and most obvious in winter when it is wet and hanging heavily.
Ecological role
Usnea longissima is an epiphyte with no nutritional link to the host tree; the fungus builds the thallus and the green algal partner provides carbohydrates, while water and minerals arrive from rain, fog and cloud. Because it absorbs everything directly from the atmosphere across a huge surface area, it is highly responsive to air quality and to drying.
The long strands provide microhabitat and nesting material for birds and invertebrates and contribute litter to the forest floor. With apothecia effectively absent, the species depends on fragmentation for dispersal — pieces must land on a suitable branch nearby — which explains its slow spread, its clumped occurrence on a few heavily colonised trees and its poor recovery once removed from a stand.
Similar species
Other Usnea species share the elastic white central cord but branch repeatedly and more or less equally, tapering toward the tips, and retain a continuous intact cortex over the whole thallus. They therefore look bushier and shinier than the long, flaking, single-cord bottlebrush of U. longissima.
Alectoria sarmentosa is pale yellow-green and pendent but has no central cord and branches freely and smoothly, without perpendicular short laterals. Bryoria species are brown to blackish, very fine and wiry, and likewise cordless. Ramalina menziesii hangs from trees in some of the same regions but its strands are flattened and fused into an open net rather than round with side branches.