Huperzia is a genus of lycophyte plants, sometimes known as the firmosses or fir clubmosses. This genus was originally included in the related genus Lycopodium, from which it differs in having undifferentiated sporangial leaves, and the sporangia not formed into apical cones. The common name firmoss, used for some of the north temperate species, refers to their superficial resemblance to branches of fir (Abies), a conifer. In Australia, the epiphytic species are commonly known as tassel ferns.
The genus has a cosmopolitan distribution, with about 400 species. Some botanists however split Huperzia into two genera, Huperzia in the narrow sense including 10-15 species of terrestrial temperate to Arctic species, and the rest in Phlegmariurus, a primarily tropical to subtropical genus of mainly epiphytic species. Huperzia and its relatives are included in the family Huperziaceae in some classifications, or alternatively in a more broadly defined Lycopodiaceae in others.
The plants of this genus generally have radial ranks of entire, linear to lanceolate evergreen leaves and dichotomously-branched (forking) vegetative stems. The spores are borne in kidney-shaped sporangia borne individually on the stem at the bases of unmodified leaves.
Unlike clubmosses, firmosses grow in clusters rather than running. The roots are produced in the tips of the shoots, growing downward in cortex to emerge at soil level. Horizontal stems are absent.