Picea abies, commonly known as the Norway spruce, is a species of spruce native to northern, central and eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, at 9 to 17 centimetres (3.5 to 6.7 in) long. It is very closely related to the Siberian spruce, which replaces it east of the Ural Mountains, and with which it hybridizes freely. The Norway spruce has a wide distribution of planting for its wood, and is the species used as the main Christmas tree in several countries around the world. It was the first gymnosperm to have its genome sequenced. This young female Norway spruce cone, with a length of 43 millimetres (1.7 in) at the time of pollination, was photographed in Keila, Estonia.Photograph credit: Ivar Leidus