Herb, uncertain whether solitary or ‘social’. Stem subterranean, short and thick, white, with endotrophic mycorrhiza, each year usually producing one thick root and one leaf, rarely several leaves. The entire plant in Bockfjorden (Elvebakk et al. 1994) seems to be 2–3 cm tall.
Leaves single, erect from the stem, at base with a fibrous sheath, divided near the middle into a vegetative and a reproductive blade (the vegetative blade lateral to the main growth direction). Petiole and vegetative blade bright green. Vegetative blade triangular in outline with 3(4) pairs of opposite, triangular or rhombic pinnae, shallowly crenate or lobed. Reproductive blade branched with opposite branches with sessile sporangia.
Sporangia sessile in two rows along the lobes of the reproductive blades, usually very few in Svalbard plants (12 observed in the photo from Bockfjorden, Elvebakk et al. 1994), yellow, opening by a split.
Sexual reproduction by spores; probably some very local vegetative reproduction by detachment from the subterranean stem. Spores are liberated passively when the sporangia split.
Spores are wind dispersed but perhaps mostly over short distances.
The only similar plant in Svalbard is the other species of Botrychium, B. lunaria, with oblong vegetative blade and pinnae that are more semilunar to reniform and mostly entire.
Botrychium boreale has been reported twice in Svalbard, once in a moss–Bistorta vivipara–Salix polaris carpet close to thermal springs with a stable water temperature around 15—23ºC, and once in more ordinary tundra together with Carex rupestris, Micranthes hieraciifolia and Pedicularis hirsuta (for both sites, see Elvebakk et al. 1994).
Thermophilous. Both sites are in the middle arctic tundra zone and the weakly continental section. Known from the close surroundings of the thermal springs in Svalbard, Trollkjeldane at Bockfjorden (Haakon VII Land, discovered in 1981, see Elvebakk et al. 1994), where a single blade (plant) was found, and from Andréedalen (Andrée Land, discovered in 1990, see Elvebakk et al. 1994), also this find of a single blade. The species was searched for but not found at Trollkjeldane in 2009 and 2013. The report from Bockfjorden is fully reliable. The one from Andréedalen is probably also correct, but we are very reluctant to accept that the photo of the Andréedalen specimen reproduced by Elvebakk et al. (1994: 138) stems from a Svalbard plant (allegedly collected by H.-J. Schweitzer and deposited in his private herbarium); compare with the Bockfjorden photo on p. 136.
The species in its current-day circumscription is amphi-Atlantic in NW Siberia, N Europe and S Greenland. Reports from the Beringian regions refer to the related Botrychium pinnatum H. St. John (see Elven et al. 2011).
The two blades or shoots of Botrychium boreale found in Svalbard suggest a nearly cryptic existence where the subterranean and mycotrophic stem can live for a very long time and send up a blade with sporangia at very rare intervals.
Elvebakk, A., Elven, R., Spjelkavik, S., Thannheiser, D. & Schweitzer, H.-J. 1994. Botrychium boreale and Puccinellia angustata ssp. palibinii new to Svalbard. — Polarflokken 18: 133—140.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/
Söyrinki, N. 1989. Fruit production and seedlings in Polygonum viviparum. – Memoranda Societatis Fauna Flora Fennica 65: 13–15.