Flora of the Canadian Arctic Archipelago

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S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Juncus triglumis L. s.l.

English: Northern white rush,

French: Jonc blanchâtre,

Inuktitut: Nunarakuluit malikaat ajjikasangit (Baffin Island), Iviit, ivisuka, ivitsuskaka (Nunavik).

Juncaceae, Rush family.

Published in Kongl. Svenska Vetenskapsakad. Handl. 8(5): 241. 1962.

Synonymy. Juncus triglumis L. var. albescens Lange, Consp. Fl. Groenl. 123. 1880.

Juncus albescens (Lange) Fernald, Rhodora 26: 202. 1924.

Vegetative morphology. Plants 3–18 cm high (to 35 cm high on continental North America; 0.3–0.5 mm wide); perennial herbs; caespitose. Only fibrous roots present. Ground level or underground stems absent. Aerial stems erect (stiffly). Leaves mainly basal; alternate; dying annually and non-persistent. Petioles absent. Sheaths present; with the margins not fused. Ligules absent. Leaves grass-like. Blades 15–80 mm long, 0.3–1 mm wide (in diameter), straight, linear, with sheath auricles (slightly prolonged, scarious or slightly leathery), folded (often pressing flat; usually shorter than the culms), veins parallel. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blade margins glabrous; apices acuminate.

Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves (scale-like, subtending the inflorescence), or without leaves. Leaf or reduced bract subtending the base of the inflorescence present; reduced, or scale-like; exceeding the inflorescence (apex obtuse to mucronate, subsp. triglumis), or similar in length to the inflorescence, or shorter than the apex of the inflorescence (apex long acuminate, or awned subsp. albescens). Flowers in inflorescences (flowers tightly clustered and superficially appearing as a single unit). Flower orientation flowers side by side in a horizontal plane. Inflorescences head-like (flowers tend to be side by side rather than one above the other as in J. biglumis); terminal; dense; 0.4–0.6 cm long. Pedicels absent. Bisexual spike(s) with empty bracts at the base (short and scaly). Floral bracts apices entire. Flowers per inflorescence 2–5 (Arctic specimens, to 50 in plants from continental North America; inflorescence cluster 4–7 mm wide); small. Sepals conventional (brown tepals); 3; free; yellow (straw-coloured), or brown (reddish); scarious. Calyx glabrous. Petals conventional (brown tepals); free; same length as the calyx; 3; yellow (albino form), or brown (and scarious); without contrasting markings; lanceolate; unlobed; 4–5 mm long; 0.9–1.1 mm wide. Stamens 6. Anthers 0.7–0.9 mm long. Ovary superior; carpels 3; syncarpous. Styles 3; free; 0.5–0.6 mm long (stigmas equally long). Stigmas per ovary 3. Ovules per ovary 10–20 (estimate). Fruit sessile; with calyx persisting; dry; a capsule (well exserted from the perianth, subsp. triglumis; or barely exserted from the perianth, subsp. albescens); ellipsoid (apex rounded without a hollow notch; this contrasts with Juncus biglumis; apex conic or rounded proximal to the persistent style, subsp. triglumis: apex nearly truncate, proximal to the persistent style, subsp. albescens); yellowish, or brown (tan; pseudo-3-locular); 3–7 mm long (4.5–7 mm long subsp. triglumis, or 3–5 mm long subsp. albescens); 1–2 mm wide; not distinctly flattened; dehiscent. Seeds 10–20 (estimate); 0.5–1 mm long (body; tails 0.6–1 mm long); brown (tan or darker).

Chromosome information. 2n = 2n = about 130. Jørgensen et al. (1958, Greenland, 'triglumis'); Yurtsev and Zhukova (1978, eastern Chukotka);

2n = 132. Löve (1981d, central Canada);

2n = about 134. Holmen (1952, Greenland).

Ecology and habitat. Substrates: wet meadows, around the margins of ponds, depressions of low-centre polygons (and in the centre of frost boils), marshes, along streams, river terraces, lakeshores (near deltas), tundra, slopes (wet), ridges (sand ridges and saturated silty beach swales), seashores (muddy flats just above tide level); imperfectly drained moist areas, seepage slopes (in Europe a mire and marsh specialist, almost everywhere in closed vegetation on turf); gravel, sand, silt, clay, till; with high organic content, peat (occasionally); acidic (reported on granite; CAN 259351), or calcareous (predominantly).

North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago widespread. Common. Arctic. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Banks, Victoria, King William, Southampton, Coats.

Northern hemisphere distribution. Amphi-Atlantic, or amphi-Beringian, or North American. Svalbard – Franz Joseph Land, Yana–Kolyma, West Chukotka, Wrangel Island, South Chukotka, East Chukotka, West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay, Ellesmere Land – Peary Land, West Greenland, East Greenland.

General notes. Polunin (1940a) noted that this taxon is very common in the extreme south of the flora area but only occasional north of the Arctic Circle, where its place is largely taken by the earlier flowering, and otherwise better adapted, J. biglumis. Like that species, with which it is often associated, it grows chiefly in rather open areas of damp mud or clayey soil. Rarely more than 15 cm high, and often only 5–10 cm high, it is easily overlooked except when flowering, and hence rarely to be found in the collections of amateurs even from areas where it is plentiful. The distribution map presented here shows several more records for Ellesmere and Axel Heiberg Islands since Porsild (1957).

Porsild (1957, 1964) and Porsild and Cody (1980) referred all Canadian populations of J. triglumis s.l. (at least east of Mackenzie River), as well as the Greenland populations, to J. albescens. Hultén (1968) considered J. triglumis s.s. to be circumpolar.

The reported ploidy difference is an argument for recognition of J. triglumis (2n = 50) and J. albescens (2n = 130 – 134) as species, but the morphological and geographical data are ambiguous. A correlation between ploidy level and morphology is still not well established. Löve and Löve (1956) reported, e.g., both 2n = 50 and 2n = about 134 from Iceland where only J. triglumis s.s. is known to occur. At least one of the 'triglumis'-level counts is North American, disproving a North American (albescens) and Eurasian (triglumis) disjunction. Elven et al. (2003) favoured subspecific status for the two taxa. Brooks and Clemants (2000) accepted both (as varieties) for North America, largely as sympatric, but with 'albescens' as the most widespread. If the morphological distinctions are connected to the ploidal levels (this fact is not yet established), the choice is rather between two species or one polymorphic species, and rank as variety or subspecies is then inappropriate (Elven, personal communication, 2005).

Juncus triglumis is often reported as colonising silty disturbed areas, and tends to be locally sparse. It can be found in numerous habitat types, however, and at varying altitudes from coastal swales to upper mountain slopes as high as 1000 feet above sea level (CAN 370914). In tundra meadows, it can be found in Carex communities along with J. biglumis. In coastal wetlands, it occurs in extensive marshes with Eriophorum and Carex aquatilis var. minor. On black, mucky seepage slopes, it grows with Kobresia simpliciuscula and Eriophorum callitrix. On southern Baffin Island at Ogac Lake, it was reported in this habitat type with Trichophorum cespitosum and Pinguicula vulgaris (CAN 302048).

Juncus triglumis was found to be an early coloniser of oil spills in Alaska (Kershaw and Kershaw 1986).

Illustrations. • Habitat: Baffin Island. Flowering plants up to 5 cm tall, growing in sand beside a runoff trickle. Nunavut, Baffin Island, near Mt. Joy, Soper River Valley. Aiken and Iles 02–046. CAN. • Habitat. Plants growing beside a road in a disturbed, wet area. Nunavut, Baffin Island, Iqaluit. 27 August, 1997. Aiken 97–050. Scale bar in cm. • Close-up of plant. Plant growing in gravelly meadow. Nunavut, Baffin Island, Iqaluit. 24 July, 1982. J.M. Gillett 19021. CAN. • Close-up of inflorescence. Plants less than 6 cm high. Flowers subtended by short bracts. CAN 292067. • Close-up of two inflorescences. Inflorescences usually appear terminal on the stem, each flower in the axil of a short subtending bract. The flowers tend to be 'side by side' rather than 'one above the other' as in Juncus biglumis. Left, inflorescence with three flowers. Right, inflorescence with two flowers. CAN 292067. • Close-up of inflorescence. Fruiting inflorescences with capsules that have pointed apical tips. This character distinguishes the species from Juncus biglumis which has notched capsules. • Arctic Island Distribution.


This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.

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