We have a Professor in the field of muscology (yes, the study of mosses) here in University where I am based at and believe me, it is difficult to get them IDed.
You may want to check out this
link for more information.
Chapter four is relevant and here is a short excerpt:
4.2 Sphagnum Taxonomy
Sphagnum mosses belong to one of two genera in the family Sphagnaceae, class Sphagnopsida, Division Bryophyta. There are approximately 100 species found in North America, with 27 species
reported for western Washington (Crum, 1984). Thirteen species found (to date) in King County (Cooke 1997). Taxonomy used will follow McQueen and Andrus (in press).
The genus Sphagnum has been divided into ten Sections based on cortical cell anatomy, hyaline cell anatomy, number of branches per fascicle, branch color, branch leaf shape, position of green cells, the presence of fibrils, and habitat preference.
Six of the ten sections of the genus Sphagnum are represented in Washington State. There are six species in the Section Sphagnum (S. magellanicum, S. centrale, S. henryense, S. palustre, S.papillosum, and S. alaskense). These species have many characteristics in common; their cortical cells are reinforced with fibrils, and they have broad branch leaves that are blunted and concave, and have toothed backs.
There is only one species in the Section Rigida (S. compactum). Species in this section have uniform cortical cells that have a single pore at the upper end, very small stem leaves, and broadly truncate branch leaves with toothed margins.
There are two species in the Section Subsecunda (S. subsecundum and S. contortum). These species have branches with five or fewer fascicles and a small curved-branch capitulum. They are orange-yellow with a tinge of green, and have branch leaves arranged to one side. The branch leaves have hyaline cells that are arranged in bead-like rows along a seam down each hyaline cell for the length of the leaf.
The ten species of the Section Acutifolia (S. fimbriatum, S. girgensohnii, S. warnstorfii, S. russowii, S. fuscum, S. rubellum, S. bartlettianum, S. capillifolium, S. subnitens and S. rubiginosum) have five or fewer fascicle branches and have triangular or trapezoidal green (photosynthetic) cells in the branch leaves.
The six species in the Section Cuspidata (S. lindbergii, S. riparium, S. annulatum, S. mendocinum, S. pacificum, S. angustifolium) are green or brown, have elongate and tapered branch leaves, and have the green cells exposed on the inner (ventral) surface of the leaf. These species are usually found in wet depressions or are aquatic, and have stem leaves that are modified (resorbed hyaline cells in outer walls), occasionally to the extent that the leaf becoming split. The branch leaves are often undulate when dry.
The final Section, Squarrosa, has two representative species in Washington (S. squarrosum and S. teres). These species have branch leaves that are not undulate when dry. They are instead squarrose (leaves with the upper portion bent back at right angles to the stem).
So, which one of the 100 or so
Sphagnum species in America do you have?
Have I confused everybody yet?