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 15 cm broad or more. Flowering stems (scapes) up to 15 cm or more.

Leaves alternate, all in basal rosettes. Petioles (0.7)1.0–2.0(2.5) cm, up to 1/2–2/3 the length of blades. Blades very variable in size, most often in the range 1.0–2.0(2.3) × (0.5)0.7–1.3 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 rounded, more rarely subacute, green or bluish green, sparsely pubescent with white 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, 1.5–2.5(5) 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, not or rarely overlapping. White flowers are much more common than yellow ones. Stamens (4,) 8, ca. 16 or ca. 24. Gynoecium of 4–6 fused carpels, with a low pyramidal disc with 4–6 stigmatic rays decurrent for more than 2 mm. Stigmatic papillae short, 0.15–0.4 mm, pale green to yellow.

Fruit a globose or subglobose capsule (8)10–12(13) × (6)7–9(10) mm, broadest part some distance above the middle but narrowing immediately below 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 cornwallisense is present and frequent in all zones and sections. Whereas it constitutes 30 % of the total Papaver collections from Svalbard, it constitutes 40–60 % of the collected material in all the 'Lands' of western and central parts of Spitsbergen, from south to north: Wedel Jarlsberg, Nathorst, Nordenskiöld, Bünsow, Dickson, James I, Oscar II, Albert I, and Haakon VII. All the four specimens collected from the offshore western island of Prins Karls Forland belong to P. cornwallisense. When a Papaver is collected (or photographed) in the places people usually visit in Svalbard, there is an even chance that it is P. cornwallisense rather than P. dahlianum. In the eastern parts of Spitsbergen and in the other islands, it seems to be very rare. There are only one collection each from the eastern Spitsbergen 'Lands' of Sabine, Olav V and Andrée, and Ny-Friesland, and only one collection each from the islands of Nordaustlandet (in Gustav V Land: Kinnvika) and Barentsøya. As far as the herbarium specimens tell, P. cornwallisense has not yet been recorded from Kong Karls Land, Edgeøya (but see Little 2013), Hopen, or Bjørnøya.

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 reaches 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. cornwallisense is a common plant in N and especially in NE Greenland (but not reaching much southwards) and in the Canadian Arctic Archipelago westwards to Banks Island and southwards to the entrance of Hudson Bay (Southampton Island), see Solstad & Elven (in prep.). It does not reach Alaska or Beringia and there is no record whatsoever from Russia. Papaver cornwallisense in Svalbard therefore most probably originates from Greenland or Canada.

In most arctic regions, several species of Papaver co-occur, probably with little hybridization. Through more than 15 years of field work with arctic Papaver, 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.

For the name P. polare, see P. dahlianum.

Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.

Baskin, C.C. & Baskin, J.M. 2001. Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. – London: Academic Press.

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/

Engelskjøn, T. & Schweitzer, H.J. 1970. Studies on the flora of Bear Island (Bjørnøya). I. Vascular plants. – Astarte 3: 1–36.

Hadač, E. 1942. Notulae ad floram Svalbardiae spectantes. – Studia Botanica Cechica 5: 1–5.

Hadač, E. 1944. Die Gefässpflansen des "Sassengebietes", Westspitsbergen. – Norges Svalbard og Ishavs-undersøkelser 87. 72 pp. + XIV Tafel.

Hadač, E. 1960. The history of the flora of Spitsbergen and Bear Island and the age of some arctic plant species. – Preslia 32: 225–253.

Hagen, D. 2002. Propagation of native Arctic and alpine species with a restoration potential. – Polar Research 21: 37–47.

Little, L. 2013. The role of flower colour in polar regions. – PhD. Thesis (submitted 2013), Univ. Otago, Otago, New Zealand.

Löve, Á. 1955. Cytotaxonomical remarks on the Icelandic Papaver. – Nytt Magasin for Botanikk 4: 5–18.

Müller, E., Cooper, E.J. & Alsos, I.G. 2011. Germinability of arctic plants is high in perceived optimal conditions but low in the field. – Botany 89: 337–348. Doi 10.1139/b11-022.

Nordal, I., Hestmark, G. & Solstad, H. 1997. Reproductive biology and demography of Papaver radicatum – A key species in Nordic plant geography. – Opera Botanica 132: 77–87.

Solstad, H. 2009. Taxonomy and evolution of the diploid and polyploid Papaver sect. Meconella (Papaveraceae) – PhD. Thesis, Univ. Oslo, Oslo.

Solstad, H. & Elven, R. in prep. Revision of Papaver L. sect. Meconella (Papaveraceae) in non-Beringian arctic North America including Greenland.

Solstad, H., Eriksen, P.B., Little, L. & Elven, R. 2014. To valmue-arter på Svalbard, og litt om fjell- og polarvalmuer. – Blyttia 72: 187–196.

Sunding, P. 1962. Høydegrenser for høyere planter på Svalbard. – Norsk Polarinstitutts Årbok 1960: 32–59.

Steen, S.W. 1998. Population structure and RAPD phylogeography of Papaver dahlianum in Svalbard. – M. Sc. Thesis, Univ. Oslo, Oslo.

Wilhelmsen, A.M. 2007. Klimaeffekter på frøspiring og blomstring hos svalbardvalmue (Papaver dahlianum Nordh.). – M. Sc. Thesis, Univ. Tromsø, Tromsø.