Solitary herb with a central root and a subterranean stem as a vertical, simple or branched caudex supporting one to several leaf rosettes forming tussocks up to 20 cm broad or more. Flowering stems (scapes) up to 20 cm or more.

Leaves alternate, all in basal rosettes. Petioles 1–4(5) cm, up to 1/2–2/3 the length of blades. Blades very variable in size, mostly in the range (1.0)1.2–2.6(3.0) × 0.8–1.8(2.0) cm, ovate, oblong or obovate in outline, deeply lobed with (1)2–3 pairs of lateral lobes and a terminal lobe, lobes contiguous or overlapping, lobe apices subacute, more rarely rounded, green or greyish green, sparsely to densely pubescent with long, white or yellowish hairs.

Flowers singly on ascending to erect, leaf-less scapes from the rosettes. Scapes with dense, patent, dark brown to blackish hairs.

Buds globular to ovoid, densely covered by blackish hairs. Flowers radially symmetric, 2–5(6) cm in diameter, with 2 sepals fused as a hood (caducous, i.e., falling off before or at anthesis) and 4 petals. Flowers cup-shaped and changing direction following the orbit of the sun (parabolic). Petals obovate or broadly obovate, usually overlapping, varying significantly in size between populations. White and yellow flowers are equally common. Stamens numerous (more than 24). Gynoecium of 5–7 fused carpels, with an almost flat disc with 5–7 stigmatic rays decurrent for 1–2 mm. Stigmatic papillae long, 0.6–1.2 mm, pale green to yellow, often remaining as a tall fringe also into the fruit stage.

Fruit an urn-shaped (pyriform) capsule 10–14(15) × (4)5–9(10) mm, with its broadest part at the very top, just at the transition to the disc, with one room and numerous seeds attached along the sutures between the carpels. Capsule opening by pores under the disc, number of pores the same as number of stigmatic rays.

Sexual reproduction by seeds; no vegetative reproduction. The following information concerns both P. dahlianum and P. cornwallisense as the two species have not been kept apart until very recently. A single plant of Papaver in Svalbard often produces 10 or more flowers, each flower a capsule with 40 or more seeds. Flowers and fruits are rarely damaged by bad weather but grazing (reindeer and birds, especially snow buntings) reduces the seed output appreciably in many areas. The seeds have a combination of morphological and physiological dormancy (Baskin & Baskin 2001) and germination percentages are low (Müller et al. 2011; Alsos et al. 2013) but may be 60–80 % after 2–6 weeks of cold stratification following a warm stratification (Hagen 2002; Wilhelmsen 2007). Whereas no germination was observed one year when seeds were sown outdoor in Svalbard, 12–15 % germination was observed the following year (Müller et al. 2011).

The scapes stiffen in the fruit stage and contribute, together with the pores, in ballistic spread of seeds. Farther dispersal may be mainly by wind or birds.

Until recently only one species of Papaver has been assumed present in Svalbard: P. dahlianum. The recognition of also P. cornwallisense being present has been suspected from 2009 and onwards and was finally confirmed in 2013 (see Solstad et al. 2014). The two species are similar in many morphological features but they differ distinctly in other features, in molecular markers, and probably has allopolyploid origins from different combinations of more low-ploid parents (see Comments). The best diagnostic differences are found in the number of stamens, the stigmatic papillae, and the shape of the fruit. Papaver dahlianum has numerous stamens (more than 24), very long and 'fuzzy' stigmatic papillae (0.6–1.2 mm) that often remain as a tall fringe also into the fruit stage, the fruit is urn-shaped and broadest at the very top, just at the transition to the disc, and the disc is almost flat with stigmatic rays shortly decurrent (up to 2 mm). Papaver cornwallisense has (for a Papaver) unusually few stamens (4, 8, ca. 16 or ca. 24), short stigmatic papillae (0.15–0.4 mm), the fruit is globular or subglobular with its broadest part well below the disc but above the middle, and a low pyramidal disc with stigmatic rays long decurrent (more than 2 mm). Less diagnostic differences are that P. cornwallisense has smaller flowers than P. dahlianum, usually white petals (almost equally frequent white and yellow in P. dahlianum), and the leaves of P. cornwallisense are less hairy, slightly more bluish green, and with more obtuse lobes than in P. dahlianum.

This information is in common for P. cornwallisense and P. dahlianum. We have so far not seen any noteworthy difference in their habitat. The Papavers are among the hardiest of all arctic vascular plants, P. cornwallisense perhaps even hardier than P. dahlianum. They usually grow in poorly vegetated rocky sites with little or no competition from other plants. Examples of site types are moraines, fell-fields, unstable slopes, patterned ground, mountain plateaus and tops, river bars, screes, and other disturbed sites. They grow on well or moderately well drained, mixed or coarse substrates. Papaver also seems to be somewhat indifferent to snow cover during winter, occurring both in exposed and in quite protected sites with snowbed characteristics. Both species are largely indifferent as to soil reaction (pH).

Papaver dahlianum is common in all zones and sections and present on all major and most minor islands, including Kong Karls Land, Hopen and Bjørnøya. On these latter islands, and also on Edgeøya, it is the only Papaver documented by herbarium vouchers (but see Little 2013 for Edgeøya), and it is the predominant one on Nordaustlandet, Barentsøya and the eastern parts of Spitsbergen. There is a sharp transition between the eastern and western parts of Spitsbergen: in the eastern parts P. dahlianum predominates, whereas in the western parts P. dahlianum and P. cornwallisense are almost equally frequent (both 40−60 %). Papaver is the vascular plant recorded at the highest elevation in Svalbard, with altitudinal limit at 940 m a.s.l. on Nordenskiöldfjellet by Longyearbyen (Sunding 1962). It is not known which of the two species that reach this altitude. Both are common on the mountains in the surroundings of Longyearbyen but only P. dahlianum has been collected from just that mountain, and the altitude record is not supported by any collection in the herbaria. Outside Svalbard, P. dahlianum is a common plant in N Greenland (reaching much farther southwards than P. cornwallisense both on the east and the west coast) and in the Canadian Arctic Archipelago westwards to Banks Island. It does not reach Alaska or Beringia; however, an undescribed species at a lower ploidy level, possibly a close relative of P. dahlianum, is found in N Alaska (P. murrayi Elven & Solstad ined.). Eastwards, there are records from Franz Joseph Land (with genetic support), Novaya Zemlya, and Taimyr (with genetic support), and the species is present in N Fennoscandia and was originally described from the Varanger Peninsula in NE Norway. It is also probably present in the Murman area in NW Russia (as P. lujaurense N.Semenova).

In most arctic regions, several species of Papaver co-occur, probably with little hybridization. Through more than 15 years of field work with arctic Papavers, we have seen only one possible hybrid population (in N Siberia). However, in gardens many species of Papaver hybridize when grown together (see old studies listed by Solstad 2009). The lack of extensive field hybridization may be partly due to differences in ploidy levels where all levels from diploid (2n = 14) to dodecaploid (2n = 84) or even higher are known among arctic representatives, partly to an assumed high level of inbreeding among arctic species of Papaver, and partly to genetic incompatibility besides the ploidy differences.

In Greenland, four species are common in parts of the island (P. cornwallisense, P. dahlianum, P. labradoricum, P. lapponicum), all four also in the eastern parts and three in the parts closest to Svalbard (P. labradoricum is more southern), see Solstad & Elven (in prep.). In arctic European Russia, at least two species occur (P. dahlianum and P. lapponicum, the latter with at least two subspecies). Until recently, Svalbard has been the only significant arctic region with only one species of Papaver present.

Papaver dahlianum and P. cornwallisense are both high polyploids (2n = 70, perhaps also 2n = 84 in P. cornwallisense, see Elven et al. 2011). They are genetically distinct (Solstad 2009; based on AFLP markers) and no hybridization has been observed or is suspected, even if they are largely sympatric and often grow in mixed stands throughout N Canada and N Greenland (Solstad & Elven in prep.), and Svalbard (Solstad et at. 2014). Their origins from diploid or lower polyploid progenitors may be rather different, making hybridization a rare event and hybrids sterile and short-lived. In their AFLP patterns, they both show affinity to Beringian species as possible progenitors, but to different ones (Solstad 2009). The morphological similarity may be due to ecological convergence in similar environments but perhaps rather to some shared progenitor besides the different Beringian ones.

A sample of 16 individuals from numerous populations in Svalbard were included in the AFLP study of Solstad (2009), but only one genetic group was found, connecting closely to P. dahlianum from the Varanger Peninsula in NE Norway (the type region of this species). We were therefore sceptical when we in 2013 found that the herbarium specimens from Svalbard included 30 % specimens conforming to P. cornwallisense morphologically. We have re-checked the Svalbard voucher specimens collected for Solstad's AFLP study. Whereas they include both species, the selection analysed for AFLPs included only morphologically identifiable P. dahlianum.

Presence of more than one species in Svalbard has been suspected for some time. An early, very observant botanist was Emil Hadač (1942, 1944), describing informally the variation found in the Adventfjorden area in Spitsbergen (near Longyearbyen) as possible races (Hadač 1942, 1944). His suggestions were taken up by Löve (1955) who formally described the proposed races as two varieties of P. dahlianum, and Hadač (1960) raised one of these to rank of subspecies. We have inspected the type specimens of the Hadač/Löve races (in the Oslo herbarium, O) and both belong to P. cornwallisense. Another indication was found in the early molecular study of Steen (1998, based on RAPD markers). He found an east–west variation in Svalbard P. dahlianum that he explained as a geographical change in gene frequencies within one species. We can now explain this more simply as a change in frequency of two species. A similar pattern has recently been found by Little (2013), also suggesting that the genotype of P. cornwallisense may be present on Edgeøya.

The name P. polare (Tolm.) Perfil., based on P. radicatum ssp. polare Tolm., has been problematic to assign until now. Tolmachev (1923) described his new race from several regions in the North Atlantic areas, from Greenland and Iceland eastwards across Svalbard to arctic Russia, and thereby included parts of the ranges of 3–4 species: P. radicatum s. str. (Iceland), P. lapponicum (Greenland and Russia), P. dahlianum (probably Greenland, Svalbard, and Russia) and P. cornwallisense (at least Svalbard) within its circumscription. The name P. polare was therefore impossible to assign to any species until Egorova (1998) chose a type for the name from the Longyearbyen area in Spitsbergen, Svalbard. The identity of this type specimen (deposited in the Komarov Herbarium, LE, in St. Petersburg), as belonging to either P. dahlianum or P. cornwallisense, is essential for the correct application of the name P. polare. The name has usually been considered synonymous with P. dahlianum but with some exceptions, e.g., Nilsson (2001; as P. dahlianum ssp. dahlianum in mainland Norway and ssp. polare in Svalbard) and Kiger & Murray (2003; as P. radicatum ssp. polare and as specifically distinct from P. dahlianum). These authors have all considered the Svalbard plants to belong to a single taxon, different from the mainland Norwegian plants at some level, a view countered by the study of Solstad (2009). None of the mentioned authors have considered P. cornwallisense as distinct from P. polare. The type material has now been studied, has many stamens, long stigmatic papillae, and belongs to P. dahlianum. The name P. polare is then a later synonym as the name 'dahlianum' was coined for a species in 1932, 'polare' in 1936 (see Solstad et al. 2014).

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