Lycopodium erubescens Brack.; Huperzia somae (Hayata) Ching; Lycopodium chinense Christ var. somae (Hayata) Masam.; L. rubricaule Alderw.;  L. somae (as "somai'') Hayata; Urostachys erubescens (Brack.) Herter ex Nessel; U. erubescens var. baldwinianus Herter ex Nessel; U. erubescens var. linaris Hillebr. ex Nessel; U. rubricaulis (Alderw.) Herter ex Nessel; U. somae (Hayata) Herter ex Nessel; U. yakusimense Masam. ex Nesse

Indigenous

Latin erubescens, reddening, blushing, m reference to the color of the stem of this species.

Plants delicate, herbaceous, terrestrial. Stems erect, decumbent at bases, narrow, 4-12 x 0.4-0.8 cm, smaller toward tips of stems, often 1-to 2-branched, usually pink to red annual constrictions absent. Leaves spreading to reflexed, narrowly lanceolate to sublinear, 2-4 x 0.7-1 mm, margins entire, tips acute. Gemmae 2-3 x 2-3 mm. Infrequent, but locally common, in wet, boggy, mossy, usually open areas, 800-1,645 m, all major islands except Lana'i. Its native range also includes Japan, Taiwan, and the Philippines.

There is disagreement on the correct scientific name for this Huperzia species, hinging on whether the spores on the type specimen are malformed or merely immature. The name used here is based on the interpretation that the spores of the type specimen at the U.S. Herbarium are normal (i.e., probably viable) but immature. There is agreement that the isotypes at the Bishop Museum have normal spores. If the type specimen was interpreted as a sterile hybrid with abortive spores, Huperzia somae (Hayata) Ching would be the correct name.

Huperzia erubescens may be recognized by its narrow, usually pink stems and fine smooth-margined, narrow, lanceolate leaves.