Solitary herb growing as distinct individuals with a shallow root system and all branching above ground. Stems are dichotomously branched (unique among Svalbard plants), at base into several nearly equally long shoots, forming a distinct tuft. Shoots 3–8 cm long, 4–6(8) mm broad, densely covered by imbricate leaves. For sporangia and bulbils, see Reproductive organs.

Leaves in irregular and alternating whorls of 4–6 leaves each, in 8–10 irregular rows along each shoot. Leaves 3.5–5.5 × 0.8–1.2 mm, narrowly triangular, acute to apiculate, margin entire to subentire (may have a few, indistinct teeth), yellowish green.

Sporangia singly in the axils of ordinary leaves (not in strobili as in Lycopodium or Diphasiastrum), in a zone at the middle part of each year's growth, usually retained for several years after they are emptied of spores. Sporangia reniform, ca. 1 × 1 mm, opening by a transversal split. Spores abundant, yellow(ish).

Bulbils are normally formed in the leaf axils in a zone in the upper part of each year's growth. Even if they are shed the first year, the leaves that were pressed outwards by the bulbils persist for often 5–10 years or more and give the shoots a characteristic appearance. The bulbils are bud-like, flat dwarf shoots with very few leaves.

Sexual reproduction by spores; vegetative reproduction by bulbils. Arctic plants have been assumed to reproduce mainly or entirely by bulbils but sporangia with well-formed spores (or emptied sporangia from previous years) prevail in the majority of Svalbard plants inspected (see Comments). Spore maturation takes place in autumn and may last into the next summer.

The spores are dispersed by wind. The bulbils are ballistically thrown off when something touches the plant, e.g., an animal, and probably by strong winds, too. Bulbils are probably the main agency of local sustenance of populations, spores of more long distance dispersal.

No similar plant occurs in Svalbard. For comparison with other species of Huperzia, see Comments.

Most common in heaths with some snow protection, dry snowbeds, and boulder fields and scree, often protected among stones. The species seems to be acidophilous, more common in areas with circumneutral or acidic substrates than in those with basic ones, in the latter often confined to hollows with deposition of much litter isolating the roots from the basic soils.

Frequent in Spitsbergen north of Van Keulenfjorden, with one locality on Edgeøya, one on Prins Karls Forland, and several in the inner fjords of the western and northern parts of Nordaustlandet. Absent from Bjørnøya. Present in all zones except the polar desert and all sections except the weakly oceanic.

The global range depends on how the species is circumscribed. In our circumscription, it is circumpolar and reaching south in some boreal mountains, in Europe to S Norway.

Huperzia is an uncommonly complicated genus of pteridophytes and urgently in need of a thorough, combined morphological, cytological and molecular study. There are two models for handling the variation in the northern regions, either as subspecies (assuming transition in characters) or as species (assuming discontinuity in characters). The former model is applied by Rothmaler (1993; Flora Europaea), Elven in Lid & Lid (1994; Norsk flora), Hämet-Ahti et al. (1998; Retkeilykasvio, the Finnish national flora), Kukkonen (2000; Flora Nordica), and Mossberg & Stenberg (2003; Nordiska floran). The latter is applied by Wagner Jr. & Beitel (1993; Flora of North America) and and Elven et al. (2022; Norsk flora). Arguments for the former model are assumed transitions. Arguments for the latter are that the plants seem to be at several ploidy levels, that intermediates have aborting spores and seem to be sterile hybrids, sometimes turning to bulbil production, and that in North America allopolyploid species with known parentage are proven (strongly indicating that the parents are species rather than subspecies, see Wagner Jr. & Beitel 1993). A special complication is the treatment of Wagner Jr. & Beitel. These authors left almost the entire Arctic of North America and Greenland white in their maps, perhaps assuming that only bulbil-reproducing hybrids occur there. In fact, Huperzia is rather frequent in the American Arctic and produces well-formed spores there, as elsewhere. These authors argue, however, well for a solution with several species.

The N European material can be divided on three morphological groups by us interpreted as three species: H. selago (L.) Bernh. ex Schrank & Mart. s. str. with spreading or patent, dentate, green leaves and few if any bulbils; H. appressa (Bach.Pyl. ex Desv.) Á.Löve & D.Löve with appressed or subappressed, usually dentate leaves (but spreading at the base of the shoots), and bulbils and remains from bulbils are seen only on the recent years' parts of the shoot; and H. arctica. Kukkonen (2000) merged H. arctica and H. appressa within his H. selago ssp. arctica, a procedure with which we do not agree. The differences are perhaps more pronounced between H. arctica and H. appressa than between H. appressa and H. selago. We (R. Elven & H. Solstad observ.) have seen the two growing together in sites in Greenland and Norway, well apart in morphology even when found only tens of meters from each other. Until a combined investigation of the kind suggested above is performed, we choose the model with three species. In any case, the Svalbard material is uniform and belongs to H. arctica in its entirety.

There has been a recent revival of interest in Huperzia, and several works from the very last years (2018–2022) may change our treatment of the variation.

For the complicated structure in chromosome numbers and for an extended discussion, see Elven et al. (2011).

Elven, R., Bjorå, C.S., Fremstad, E., Hegre, H. & Solstad, H. 2022. Norsk flora. 8. Ed. – Det Norske Samlaget, Oslo.

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/

Hämet-Ahti, L., Suominen, J., Ulvinen, T. & Uotila, P. (eds.) 1998. Retkeilykasvio. Ed. 4. – Luonnontieteellinen keskusmuseo, Kasvimuseo, Helsinki.

Kukkonen, I. 2000. Lycopodiaceae. – In: Jonsell, B. (ed.), Flora Nordica. 1. Lycopodiaceae – Polygonaceae: 1–13.

Lid, J. & Lid, D.T. 1994. Norsk flora. Ed. 6 by R. Elven. – Det Norske Samlaget, Oslo.

Lid, J. & Lid, D.T. 2005. Norsk Flora. Ed. 7 by R. Elven – Det Norske Samlaget, Oslo.

Mossberg, B. & Stenberg, L. 2003. Den nya nordiska floran. – Wahlström & Widstrand, Stockholm.

Rothmaler, W. 1993. Huperzia Bernh. – In: Tutin, T.G. et al. (eds.), Flora Europaea. 1. Psilotaceae to Platanaceae. Ed. 2: 3.

Wagner Jr., W.H. & Beitel, J.M. 1993. Lycopodiaceae Mirbel. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 2. Pteridophytes and Gymnosperms: 18–37.