S. squarrosum is commonly found growing in woodlands, but can also grow in swamps or seepage sites, but not in normally in bogs.
It tolerates a certain amount of shade, and can also be found growing near a watercourse or by waterfalls.
Here it is growing with Atrichum.
This species ranges in color from pale green to yellow-green. Their inter-tangled shoots often form loose turfs and the gametophyte can at times be partially submerged. The squarrose leaves make it easy to identify in the field.
The color of the stem can range from green to red-brown and the cortical cells do not have reinforcing fibrils.
The stem leaves are shorter than those found on branches and they typically have an ovate-lingulate to oblong-lingulate shape. The hyaline cells of the leaves are mostly not divided, however a few may be.
This species has two divergent and two-three pendent branches. These branches not only have distinctive squarrose spreading leaves, but they also are long and tapered.
S. squarrosum typically has one-two layers of cortical cells on the branch stem.
The leaves found on the branches are not only larger than those found on the stem but they give this species its “spiky” look due to their squarrose shape. A closer examination of the leaves will reveal that the basal area is broad. The apical area abruptly contracts to a point and distinctively curved away from the branch.
A cross section of the branch leaf will show that the chlorophyllose cells are ovate-triangular with the widest part being more exposed on the convex surface or equally on both surfaces.
The sporophytes are more or less abundant and mature in spring to mid summer.