Fruiting body a stipitate ascocarp; apothecia 3.0-6.0 (10.0) mm broad, at first obtuse-conic to turbinate, in age convex to nearly plane; margin lacking hairs, plane to decurved at maturity; hymenium glabrous, moist, cream to dull-brown, slightly darker at the center; outer surface glabrous, colored like the hymenium; stipe 1.0-2.0 cm long, 1.0 mm thick, enlarged towards the apex, watery-white, becoming dark-brown to blackish towards the base; surface slightly tomentose (use hand lens); odor and taste not distinctive.
Spores 9.5-17.5 x 3.5-4.5 µm, oblong-cylindrical to subfusiform, smooth; spore deposit not seen.
Solitary to gregarious on rotting stems of grasses and herbs in boggy montane meadows; fruiting in the spring shortly after snow melt; common, but rarely collected because of its size.
Edibility unknown; insignificant.
Cudoniella clavus is a small stipitate cup fungus sometimes confused with Sclerotinia veratri when found fruiting on the remains of Corn Lily (Veratrum spp.) It differs, however, in its typically smaller size, convex to nearly plane, not cupulate, apothecium, and the lack of a sclerotium at the base of the stipe. Other stipitate Ascomycetes found on plant debris in the spring include species of Dasycyphus and Hymenoscyphus. These generally differ either in color or size, often less than 2 mm.