The compact growth form in thin but dense mats and occurrence in often dessication-prone sites distinguishes Sphagnum perichaetiale
from any other species of sect. Sphagnum
. The often quite stiffly spreading branch leaves give it a strong resemblance to S. compactum
, but the latter’s small triangular stem leaves will readily distinguish that species. The branch leaf hyaline cells of S. perichaetiale
have only a few pores on their convex surface, and they are typically small, thickened, and grouped in 3s where the cell corners meet. Similar species in sect. Sphagnum
have more pores along the commissures, and they are more elliptical and not thickened. The often hemiisophyllous stem leaves are also diagnostic of S. perichaetiale
within the section.