Sphagnum cuspidatum is brown to greenish brown in color with slender green stems. Individual plants are slender and weak-stemmed, and are moderately sized compared to other peat mosses. Aquatic forms are flaccid and plumose giving a feathery appearance, whereas the emergent forms are much more compact.Branches are spread in quite obvious sickle shaped patterns, giving the capitulum a twisted appearance.The capitula is often green to yellow, tinged with red-brown in color. The leaves on the stems are triangular-ovate in shape, usually a bit longer than 1.2 mm, and are often very compact with one another. The leaves end in sharp points. Meristem tissue is often fibrillose. The branch stems are green, with pinkish coloration at the proximal ends, and the cortex region is enlarged. The leaves on the branches are ovate-lanceolate to lanceolate in shape, and are between 1.6-5 mm in length. These leaves falcate back towards the tips of the branches. When dry, they are often undulate and recurved. In submerged forms, the branch leaves can sometimes be faintly serrated. S. cuspidatum is a dioecious species. The spores produced are 29-38 -m, covered with large papillae on both surfaces, and appear to be covered in small blisters (pusticulate).S. cuspidatum can be found on wet humus under forests and on the bases of trees forming a hummock-hollow complex; in or near bogs.