Lycopodium annotinum is a perennial, creeping clubmoss with sessile strobili (cone-like reproductive structures) that occurs widely in Denali in forest, bogs, shrublands and alpine heaths. Plants are mostly prostrate, stems spreading widely, but reaching 5-25 cm off the ground. Stems increase in height each year, each year's growth marked by a distinct leafless patch on the stem that looks like a constriction. Plants eventually branch, but never reach the fan-like growth pattern of Diphasiastrum species. Leaves are needle-like, 8-ranked, with toothed margins, thin compared to other clubmoss leaves. Leaves protrude away from the stem, giving it a bottlebrush-like appearance. The strobili sessile (without naked stalk) on the tips of the vertical branches, separating it from the similar Lycopodium lagopus, which has stalked strobili.
Lycopodium annnotinum is an perennial evergreen plant and can begin photosynthesis soon after the snow melts. Strobili are usually produced mid-summer.
The visible portion of Lycopodium annotinum is a diploid sporophyte. Like all clubmosses, these plants are produced from a haploid lifecycle, which lives underground and is entirely dependent on mycorrhizae for its survival. The haploid gametophyte self-fertilizes and produces an independent, photosynthetic sporophyte (the plant described and pictured). sporophytes produce single-celled spores, which are wind-dispersed and develop into new underground gametophytes.
The clubmosses (Diphasiastrum and Lycopodium are used by the Dena'ina to make an eye wash (Kari 1995). Other species in these genera which occur primarily in forested areas were used medicinally by indigenous people throughout North America and Europe (Moerman 1998, Schofield 1989).
Lycopodium annotinum is a widespread circumboreal species. In North America, this species is widely distributed from Greenland and Labrador west to Alaska, south to the northwestern U.S., Rocky Mountains, Great Lakes States, New England, and along the Appalachian chain. In Alaska this species can be found statewide, except it is rare on the Arctic slope. In Denali, L. annotinum is common park wide, occurring in suitable habitat on both sides of the Alaska Range.
In Denali, Lycopodium annotinum is found at elevations from 91 m to 1301 m with an average elevation of 638 m. It grew at higher elevations, and on steeper slopes on north-facing aspects. It is most commonly found on moderately steep slopes (4 to 28 degrees).