Picea abies, 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, 9 - 17 cm long. It is very closely related to the Siberian spruce (Picea obovata), which replaces it east of the Ural Mountains, and with which it hybridises freely. The Norway spruce is widely planted for its wood, and is the species used as the main Christmas tree in several cities around the world. It was the first gymnosperm to have its genome sequenced, and one clone has been measured as 9,550 years old.