Witch's Hair Lichen

Witch's Hair Lichen (Alectoria sarmentosa) is a pendent fruticose lichen of the family Parmeliaceae that drapes conifer branches in pale, soft, freely branching tangles, typically 10-40 cm long. In humid coastal and montane forests it can be so abundant that whole crowns appear washed in pale green.

The genus Alectoria sits between the yellow-green beard lichens and the dark brown horsehair lichens in appearance, and its identity rests on a negative character that is easy to check in the field: unlike Usnea, there is no tough elastic cord running through the middle of the branches.

Branches are round in cross-section, smooth, shiny when dry and evenly pale greenish-yellow throughout, with fine longitudinal ridges and elongated pale pseudocyphellae marking the surface — a combination that separates it cleanly from both the beard lichens and the fine dark Bryoria.

Thallus form

Pendent to sub-pendent tufts hang from branches, usually 10-40 cm long, dividing repeatedly into fine, more or less equal branches that taper gradually. The overall texture is soft, tangled and hair-like rather than stiff or bristly.

Branch structure

Branches are round to slightly angular in cross-section and smooth to faintly grooved. The key test is to pull a branch apart slowly: Alectoria breaks cleanly with no elastic thread, whereas Usnea reveals a stretchy white cord. Broken ends show a uniform white interior.

Colour and surface marks

Colour is a pale, slightly whitish yellow-green, consistent along the whole thallus and on all sides. Scattered along the branches are pale, raised, elongate pseudocyphellae — narrow whitish streaks and low ridges in the cortex — which appear as fine paler lines with a hand lens.

Fruiting bodies

Apothecia are uncommon: pale to yellowish-brown discs 2-5 mm across, set laterally on the branches. Most colonies spread instead by fragmentation.

Witch's Hair grows on the branches and twigs of conifers — western hemlock, Sitka spruce, true firs, Douglas fir, pine and larch — and occasionally on hardwoods, in cool, humid, well-lit forest. It is most luxuriant on the outer canopy branches of mature trees, along stream corridors, in ridge-top stands catching cloud, and in coastal rainforest.

The range is broadly circumboreal, and it is particularly abundant in the Pacific Northwest of North America from Alaska to northern California, with populations across northern Europe, Scandinavia and northern Asia. Perennial and evergreen, it is present in every season and looks fullest and greenest in prolonged wet weather.

Alectoria sarmentosa is an epiphyte that takes water, minerals and nitrogen compounds directly from precipitation, fog and canopy throughfall rather than from its host, and photosynthesises through its green algal partner. Its huge surface-area-to-mass ratio makes it an effective interceptor of moisture and airborne nutrients, and heavily colonised canopies release these to the forest floor as litter.

Hanging lichen mats are an important structural element of old conifer canopies, sheltering invertebrates, supplying nesting material for birds and forming a substantial part of the winter browse layer for arboreal mammals and ungulates that feed on fallen material. Dispersal is mainly by wind-blown fragments, which is why abundance builds up in stands that have stood undisturbed for a long time.

Usnea species are the main confusion: they share the pendent pale yellow-green look but every branch contains a tough white elastic central cord, exposed by gently pulling a strand until the outer layer snaps. Alectoria has no cord at all.

Bryoria species hang from the same branches but are dark brown to near-black, much finer and wirier, and also cordless — the colour difference is decisive. Ramalina species such as R. menziesii are pale green but flattened and strap-like or netted rather than round-branched and hair-like. Evernia prunastri, if it occurs alongside, is strap-flattened and chalky white on the underside.