Papaver nudicaule, commonly called Iceland Poppy, is not actually from Iceland, but rather from Asia. It lives from Siberia to Mongolia and southwards into the mountains of central Asia as far as Afghanistan. It is mostly a plant of mountain screes and moraines, steppes and river gravels at altitudes up to 15,100 feet. Those that you find in cultivation may actually be crosses of nudicaule and one or more of its cousins. This breeding has formed a race of rather gaudy poppies commonly called Iceland poppies and generally found in catalogues and lists under the name Papaver nudicaule.
The true P. nudicaule is rather tall, about 20 inches, with solitary-flowered, rather bristly scapes. The basal leaf tufts are blue/green and covered with grey hairs. The flowers are yellow (note my photo is probably of the one commonly sold here since it is orange) and 2-3 inches across.
Those plants that are the hybrids have stems up to 24 inches tall and flowers that can be up to 7 inches across. Mine are more in the 3-4 inch range. The color range is orange, red, yellow, apricot, pink, salmon, cream and white. Semi-double forms are quite common. The first flowers open on each plant will be the largest.
These are excellent garden plants and will flowers over a long season. Ours start with the first hot weather and continue sporadically until frost. They are easy to start from seed, either directly sown in the garden, or started ahead of time in the greenhouse or on the windowsill. Although these are perennial, you may lose them to rot in wet winters. We have had ours for many years, maybe because they sit in a high spot in the garden, and therefore aren't subjected to wet feet.
These poppies make excellent cut flowers, though like the others, you need to either plunge ends of the stems into boiling water or sear them with a match or lighter. I just carry a lighter with me in the garden if I am planning to pick any of these. They are best picked when the buds are ready to burst open but have not yet done so. This will insure the longest possible indoor display (unless your cats like to play with flowers, in which case, nothing you do to the stems will prolong the life of the flowers).
There are a number of named varieties and strains. The ones we got were the 'Champange Bubbles' type which have large flowers in various shades. These are good from zones 3-10, according to one source, but I do know they can take the cold here in zone 6.
Two more kinds of poppies to go - the most common and the ones most people think of when you say poppies.