This epiphytic lichen belongs to the family Parmeliaceae and the suborder Lecanorineae, which includes six similar species.

[2] A. sarmentosa grows draped or strung over conifer tree limbs and deciduous shrub branches in Northern temperate rainforest.

[4] Areas required by A. sarmentosa are found in northern and southern temperate zones and receive high rainfall.

These lichens are similar in color and growth patterns but A. sarmentosa lacks a central chord that characterizes the genus Usnea.

species and subspecies have a global range and are found in Pacific Northwest Coast forests, including Alaska, Coastal British Columbia, Oregon, Washington, and northern California, west of Alberta and Montana.

[20] This lichen is very dependent on forest structure (Canopy height cover and composition), edge characteristics and climate.

Research has shown that Alectoria sarmentosa, characterized by its pale yellow-green coloration due to usnic acid, shows distinct ecological preferences from darker melanic hair lichens.

Studies in coniferous forests have demonstrated that this species achieves its highest abundance in more sheltered locations, particularly on north-facing slopes and in lower canopy positions where light levels are moderate.

The species has been found to benefit from humid conditions, with its cortical structure optimized for light transmission to underlying photobionts in shaded sites.

Unlike melanic hair lichens, A. sarmentosa shows less tolerance for high light exposure, especially in drier regions, due to its relatively transparent cortex when dry.

This habitat preference reflects an evolutionary adaptation where its pale pigmentation and thallus structure are optimized for photosynthetic efficiency in shadier, more humid forest conditions.

Sitka black tailed deer and Caribou eat the lichen off reachable, low branches or off of the ground when it is blown down onto the snow during winter storms.

A. sarmentosa is frequently collected for tissue element analysis as it is a sensitive tool for detection of changes in air quality.