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 10–15 leaves. Leaf rosettes 15–30 cm in diameter, with 0–5 hollow scapes usually 15–30 cm long and 4–5 mm thick. Scapes pink or purple. The entire plant is glabrous.

Leaf

Leaves 10–20 × 2–4 cm, with a winged petiole 1/4–1/5 of entire leaf length. Blade oblanceolate or spathulate in outline, broadest in the distal 1/3–2/3, with 4–6 pairs of deep, retrorse, acute and dentate lobes (a runcinate leaf), end lobe usually triangular and subobtuse or acute, green with a broad pink to purple 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 without appendages (‘horns’). Outer phyllaries 14–18, 9–13 × 2.5–3.5 mm, about half as long or more as inner phyllaries, strongly reflexed, narrowly triangular with an extended obtuse uneven apex. Inner phyllaries 12–18, 17–19 × 2.5–3.5 mm, appressed, narrowly triangular, the innermost ones with a narrow pale green 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, 16–18 mm, ending in (3)5 short, irregular teeth, yellow with a broad grey 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 × 0.9–1.1 mm, narrowly obconical, dull or slightly glossy straw coloured with moderately marked ribs and moderately dentate in the distal ¼ part, cone distinct, 0.8–1.1 mm, beak 9–10 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). The species of Taraxacum sect. Ruderalia are reported to be mostly triploid and hexaploid (2n = 24, 48, see Richards & Sell 1976). 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. Among the yellow-flowered species, Taraxacum sect. Ruderalia differs from T. brachyceras in lack of appendages (‘horns’) on the phyllaries, distinct cone at base of fruit beak, and usually more dissected leaves, from T. acromaurum in reflexed outer phyllaries and especially in fruit bodies much less dentate in upper part.

Habitat

Ruderal ground, mostly on gravelly, dry substrates. Probably indifferent as to soil reaction (pH) but favoured by nutrient supply.

Distribution

Introduced and established with persistent populations in the Russian settlements of Barentsburg (Nordenskiöld Land) and Pyramiden (Dickson Land) in the Isfjorden area, in both places with two or more stands and numerous individuals, with regular seed set and recruitment. The few specimens deposited in the herbaria are too little to evaluate the variation; however, the plants from Barentsburg and Pyramiden are rather different and probably belong to two or more different microspecies. Seedlings and juvenile plants of Taraxacum have been found also in the Norwegian settlements of Longyearbyen and Ny-Ålesund but never reaching a stage where they can be identified, not even to section.

Taraxacum sect. Ruderalia (or the T. officinale aggregate) is one of the largest groups of the genus in Europe and W Asia, with 150–200 named microspecies in Norway alone. No attempt has been made to identify the Svalbard plant down to level of microspecies. Plants of this section are introduced in most other parts of the world.

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Literature

Richards, A.J. & Sell, P.D. 1976. Taraxacum Weber. – In: Flora Europaea 4. Plantaginaceae to Compositae (and Rubiaceae): 332–343.