Dendrolycopodium dendroideum spreads by subterranean horizontal
stems, each upright shoot appearing somewhat like a small individual
tree. The lateral branches are essentially round, not conspicuously
flattened as in D. obscurum. Leaves on the main stem are
clearly spreading. The leaves along the lower surface of the branch
are about the same size as the other leaves.
Dendrolycopodium hickeyi and D. dendroideum were long
considered to be varieties of D. obscurum and the three
species can be difficult to distinguish, especially in dried specimens.
The characters by which they are separated are subtle and careful
observation and a little practice are required. Refer to the key. This species was long known as Lycopodium obscurum.