Dendrocollybia is a genus of fungus in the family Tricholomataceae of the order Agaricales. It is a monotypic genus, containing the single species Dendrocollybia racemosa, commonly known as the branched collybia or the branched shanklet. The somewhat rare species is found in the Northern Hemisphere, including the Pacific Northwest region of western North America, and Europe, where it is included in several Regional Red Lists. It usually grows on the decaying fruit bodies of other agarics—such as Lactarius and Russula—although the host mushrooms may be decayed to the point of being difficult to recognize.
Dendrocollybia racemosa fruit bodies have small pale grayish-white or grayish-brown caps up to 1 cm (0.4 in) wide, and thin stems up to 6 cm (2.4 in) long. The species is characterized by its unusual stem, which is covered with short lateral branches. The branches often produce spherical slimeheads of translucent conidiophores on their swollen tips. The conidiophores produce conidia (asexual spores) by mitosis. Because the fungus can rely on either sexual or asexual modes of reproduction, fruit bodies sometimes have reduced or even missing caps. The unusual stems originate from black pea-sized structures called sclerotia. The anamorphic form of the fungus, known as Tilachlidiopsis racemosa, is missing the sexual stage of its life cycle. It is able to reproduce at relatively low temperatures, an adaptation believed to improve its ability to grow quickly and fruit on decomposing mushrooms.