Life span

Perennial, moderately long-lived.

Growth form

Solitary or weakly mat-forming herb with a single white tap root and a darkish brown vertical caudex, more or less branched apically into a crown covered by blackish brown marcescent leaf remains. Each caudex branch ending in a rosette at ground level with 8–15 leaves. Leaf rosettes 10–20(25) cm in diameter, with 0–5 hollow scapes usually 5–15 cm long and 3–5 mm thick. Scapes pink or purple. The entire plant is glabrous.

Leaf

Leaves 10–20 × 2.5–3.5 cm, with a winged petiole 1/4–1/6 of the entire leaf length. Blade oblanceolate or spathulate in outline, broadest in the distal 1/3, with 4–6 pairs of distant, shallow (rarely deep), retrorse, acute and dentate lobes (a runcinate leaf), end lobe usually triangular and obtuse or subacute, green with a broad pale mid vein.

Inflorescence and Flower

The primary inflorescence of Asteraceae is a head (capitulum) surrounded by an involucrum of one or more rows of phyllaries (involucral bracts). The flowers sit on a flat, concave or convex receptacle, sometimes with scales (the bracts of the single flowers). The flowers are epigynous with perianth at top of the gynoecium. The sepals are always transformed into a pappus, mostly by hairs or sometimes by scales. The 5 stamens are inserted in the corolla tube and the anthers form a ring through which the style grows and pushes the pollen outwards. Gynoecium of two fused carpels, 2 stigmas. The fruit is an achene with one seed.

Inflorescence a single apical head 2.0–3.0 cm broad. Involucrum of 2 rows of dark green phyllaries, some or most of them with appendages (‘horns’) in distal parts. Outer phyllaries 10–16, 6–8 × ca. 2 mm, less than half as long as inner phyllaries, mostly reflexed, broadly or narrowly triangular with a slightly extended obtuse apex. Inner phyllaries 10–18, 15–20 × 2.5–3 mm, appressed, narrowly triangular, the inner ones with a narrow white hyaline margin. Receptacle flat, without scales. Flowers monosymmetric. Corollas ligulate (above the corolla tube all petals are fused in a long ligula facing outwards), ligulas >30, 10–15 mm, ending in (3)5 short, irregular teeth, yellow, with a broad grey to pinkish stripe on the outer surface.

Fruit

The fruit is divided into a body, a narrowly cylindrical beak with a conical thickening at the base (the cone), and a pappus as a stalked, feathery umbrella on the fruit. Fruit body 4.5–5.5 × 0.9–1.1 mm, narrowly obconical, dull straw coloured with shallow ribs and moderately dentate in the distal 25 %, cone insignificant, beak 7–8 mm, pappus rays 6–7 mm, white and obscurely dentate.

Reproduction

Asexual reproduction by seeds; very local vegetative reproduction by fragmentation of rhizome. Nearly all species of Taraxacum (and there are thousands, more than 1200 described from Europe alone) are agamospermous, i.e., with seed development independent of fertilization. Pollen may be well developed (yellow) or not (green or blackish green) but is assumed non-functional in nearly all species. Among the boreal and arctic species, sexual reproduction is suspected in only one species: the west arctic T. holmenianum Sahlin with a diploid chromosome number (2n = 16). Taraxacum brachyceras is known as tetraploid (2n = 32). Flowering and seed set is usually abundant.

Fruits are easily spread by wind due to their umbrella-like pappus.

Comparison

The runcinate leaves and the scabose heads with only ligulate flowers are unique for the genus Taraxacum in Svalbard. Taraxacum brachyceras differs from the other yellow-flowered species in Svalbard in its presence of distinct appendages (‘horns’) on at least some of the phyllaries, from T. acromaurum (Bjørnøya) in addition by its reflexed outer phyllaries and fruits with much longer beaks but distinctly fewer and shorter teeth on the upper parts of the fruit body.

Habitat

Herb vegetation on climatically favourable slopes, in early snowbeds, stable scree and places with bird manuration. On substrates with circumneutral or basic soil reaction (pH).

Distribution

Thermophilous. This species is mainly confined to the middle arctic tundra zone, slightly transgressing into the northern arctic, and to the transitional to clearly continental sections. It has an interrupted range restricted to Spitsbergen and mainly in the fjord districts from Hornsund (Wedel Jarlsberg Land) in the south to Liefdefjorden (Haakon VII Land) in the north. It is more or less regularly found in favourable sites in areas with basic substrates, especially north of Isfjorden.

The general distribution is N Eurasian with transgressions across the North Atlantic to Greenland and across the Bering Straits to Alaska.

Comments

The section Borealia, to which Taraxacum brachyceras belongs, is one of the two largest sections in the Arctic (the other being sect. Antarctica with, e.g., T. arcticum), see Elven et al. (2011) for a summary. Almost all other sections of the genus are restricted to Europe and W Asia. The section is represented by six other species in Fennoscandia, of which T. simulum Brenner (in both S and N Fennoscandia) is the most similar morphologically.

Literature

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF).