Sphagnum pacificum is considered a ruderal species, meaning that it is often seen colonizing areas that were disturbed and are capable to living in areas with poor soils. They are also found growing in coniferous forests as well as in mineral-rich swamps (in the Great Lakes).
This S. pacificum is a dioicous species. It is moderate in size, has a fairly strong stem and are usually green, yellow to yellowish brown in color.
This species tends to have a stem that is pale green to pale brown. The cortical cells are without fibrils and the cortex is composed of thin-walled cells that are enlarged and differentiated.
The stem leaves of S. pacificum are triangular to ligulate-triangular in shape, have a differing base border and are usually pressed closely to the stem. Furthermore, the border of the leaves is incurved while its apex is pointed.
The fascicle typically comprises of two divergent branches and two-three pendent branches. The branches are straight and taper a little.
The leaves on the branches are slightly undulate and are recurved when they are dry. Typically the leaf shape ranges from ovate to narrowly ovate-lanceolate. A cross section of a branch leaf will reveal that the chlorophyllose cells are broadly triangular and they are more broadly exposed on the convex (outer) surface.
The stem on the branches are green but can also have a reddish tinge at the proximal end. It is also possible to see conspicuous retort cells when looking at the cortex of the stem.
The sporophyte in Sphagnum pacificum are not commonly seen.
It is possible to observe papillae on one or both surfaces of the spores.