Fruit bodies, which may appear alone or in groups on the ground in conifer duff, are usually attached to buried woody debris, and are commonly associated with melting snow.

Similar black cup fungi with which P. nannfeldtii may be confused include Pseudoplectania vogesiaca, P. nigrella, and Helvella corium.

The species was first described by British mycologist Fred Jay Seaver in 1928, who called it Paxina nigrella in his monograph of the cup fungi of North America.

The name chosen by Korf honors the Swedish mycologist John Axel Nannfeldt, responsible for some early advances in the understanding of this fungus and other cup fungi.

Although this latter species may be difficult to distinguish by its less hairy external fruit body surface, its microscopic characters identify it more definitively: P. vogesiaca has spores that are much smaller, typically with widths of 12–14 μm.

[14] Plectania nannfeldtii is typically found at higher elevations in coniferous forests growing on wet twigs or other rotting woody debris, often in or near snow.

[14] It may grow singly, scattered or in clusters, and has been noted to have a preference for the wood of Picea engelmannii and Abies lasiocarpa as well as other conifers.

In North America, it is found in the Western United States and Canada, where it fruits from late May to early August;[13] it is common in the Sierra Nevada and in higher elevations of the Pacific Coast Ranges.