Like most members of genus Lepraria, the lichen has few distinguishing features, lacking both a medulla and sexual reproductive structures (apothecia).

[5] In some cases, because these illustrations represent the only remaining original material available, nomenclatural rules allow for these images to serve as lectotypes.

[1] Chronologically, these include Lepra (Friedrich Heinrich Wiggers, 1780),[11] Verrucaria (Philipp Gottfried Gaertner, Georg Friedrich Wilhelm Meyer and Johannes Scherbius, 1801),[12] Pulveraria (Heinrich Gustav Flörke, 1807),[13] Lecidea (Erik Acharius, 1814),[14] Patellaria (Kurt Polycarp Joachim Sprengel, 1827),[15] and Crocynia (Auguste-Marie Hue, 1924).

[20] The thallus consists of abundant powdery soredia (little balls of algae wrapped in fungus hyphae) up to 50 μm in diameter.

Overall, the appearance of the lichen can be quite variable, as sometimes it forms more or less loose cotton-like cushions, while other times it consists only of soredia that can be sparse or dense.

The photobiont partner of the lichen is a spherical (coccoid) member of the green algal phylum Chlorophyta, with a diameter of up to 18 μm.

[6] A chemical analysis on specimens of the lichen from Japan revealed several terpenes, including pavoninin-2, terpecurcumin Q, ergosterol acetate, taxuspine C, and lantadene A methyl ester.

[20] The expected results of standard lichen spot tests on this species are K− or + (producing a faint yellow colour), C−, KC−, and Pd−.

For example, another European species, Lepraria elobata, is difficult to distinguish from L. incana; not only is it similar in appearance, but it also grows on naked bark on tree trunks.

[19] Lepraria crassissima makes a thick wrinkled crust that grows on shaded, calciferous rock walls, and also has divaricatic acid.

[20] Although some authorities have placed the two taxa in synonymy,[23] a study of the type material convinced Pieter van den Boom and colleagues that L. crassissima "is a distinct species, morphologically and ecologically different from L. incana".

[24] Divaricatic acid is also found in Lepraria juanfernandezii, a Southern Hemisphere species newly described in 2018 from the Archipelago of the Juan Fernández Islands.

[28] It has been judged to be well-adapted to rugose (wrinkled) bark and cork accumulation, as seen in the old stem parts of Pseudotsuga and Quercus.

[35] In Norway, the lichen has been found inhabiting a number of distinct habitats: on tree trunks exposed to more or less direct rain, on sheltered, on dry bark under rock overhangs, on the underside of leaning trunks, in the concave parts of tree bases, and in bark recesses protected from direct rain.

In this country it has been recorded on Alnus glutinosa, Betula pubescens and B. pendula, Juniperus communis, Malus domestica, Picea abies, Pinus sylvestris, Populus tremula, and Sorbus aucuparia.

[49] Because of its ability to bioaccumulate high concentrations of caesium-137, Lepraria incana has been proposed for use as a biomonitor of this airborne radionuclide in northern Iran.

[51] Lepraria incana is relatively tolerant to sulphur dioxide; species that occur early in the succession of lichen communities are generally known to be less affected by this airborne pollutant.

[43] In Slovakia, it was one of the lichen species noted to grow in a forest contaminated with heavy metals near a historic mining area in Mlynky.