While hiking through the East Over Reservation in Marion on Saturday, I noticed a large patch of a type of clubmoss that I don’t usually see. These were interrupted clubmoss (Spinulum annotinum). Although interrupted clubmoss is native and found throughout New England, it is not generally found along the coastal plain counties like Barnstable, Dukes, and Bristol, and is therefore not generally found on Cape Cod. It always amazes me how different the plant communities can be just over the bridge. 

The stems of interrupted clubmoss are usually unbranched or sparingly branched, and are approximately 6 to 8 inches tall. Like other clubmosses, the plant spreads by horizontal stems running along the surface of the ground.  Individual leaves are arranged radially around the central stem, are 3 to 10 mm long, and have minute teeth along their edges. The spore clusters are produced singly at the tips of the stalks, and resemble yellowish, papery cones, made up of slender-pointed bracts. The name “interrupted” clubmoss refers to the interruption or constriction along the stem of this clubmoss separating each individual year’s growth. However, it is also sometimes called stiff clubmoss or bristly clubmoss because it is prickly to the touch.

Although originally lumped together in the genus Lycopodium with other clubmosses, such as princess pine and ground-cedar, this group has since been split into separate genera based on morphology and chromosome numbers. Depending on the source you consult, this species may still be labeled as Lycopodium annotinum.