Usnea lambii was formally described by American lichenologist Henry Imshaug as a member of genus Neuropogon.

The species epithet honours Elke Mackenzie (formerly Lamb), "one of lichenology's most devoted students and an outstanding monographer".

[6] Usnea lambii grows erect and fruticulose (i.e. small and bushy), reaching up to about 2 cm (3⁄4 in) in height.

[7] It has similarities with Usnea sulphurea due to the loose nature of the medulla but can be distinguished by its branches which are not scabrid-verruculose.

It is also noted to closely resemble Usnea acromelana but has distinct differences in medulla and central strand structure.