Stiff Clubmoss is very similar to Northern Interrupted Clubmoss (Lycopodium canadense). However, Northern Interrupted Clubmoss is not listed as a separate species in the USDA Plants Database or in the book, Manual of Vascular Plants of Northeastern United States and Adjacent Canada. It is listed as a separate species in the book, Ferns of the Northeastern and Central North America (Peterson Field Guide) and The Families of Huperziaceae and Lycopodiaceae of New England: A Taxonomic and Ecological Reference by Arthur Haines. The strobili of Northern Interrupted Clubmoss typically grows to no longer than 5/8 of an inch. In addition, the upper side of the leaves have numerous stomates (pores). The leaves of Stiff Clubmoss are sparsely, but noticibly toothed. The leaves of Northern Interrupted Clubmoss are entire (untoothed) or with very small teeth.
