Cladonia grayi s. str.

Podetia to 2 (–3) cm tall, greenish or pale grey and usually with a distinct brown tinge, sometimes blackened at the base, usually unbranched, the stalk ± corticate, verrucose-areolate, often squamulose; cup regular, to 7 mm diam., rarely proliferating, sorediate, the soredia easily eroding and mixed with microsquamules. Basal squamules inconspicuous, soon evanescent. Apothecia rare, ± dark brown, on stalks developing from the scyphus margin. Thallus C–, K–, KC–, Pd± red, UV+ mauve-white (grayanic and ± fumarprotocetraric acids).

Part of a frequently recognised morphocomplex that traditionally includes Cladonia chlorophaea s. str., but that species is phylogenetically distinct and may be separable in morphological terms; the podetia in C. grayi s. lat. [BLS 2810] are browner and more completely corticate and granulose, rarely with large soredia. It is included in a subclade separate from that containing C. chlorophaea within clade Cladonia subclade Graciles (Stenroos et al. 2019), and seems to be polyphyletic.

Species within the Cladonia grayi aggregate include C. asahinae, C. cryptochlorophaea, C. merochlorophaea and C. novochlorophaea (see table under C. chlorophaea s. lat.). They are difficult to determine using morphology, and are arguably conspecific. TLC is mostly recommended to confirm identification. The presence of grayanic acid (leading to the distinctive bright UV+ mauve-white reaction) is considered to be diagnostic for C. grayi s. str., with some populations also producing fumarprotocetraric acid (Pd+ red).