A spruce is a tree of the genus Picea ( ), a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal (taiga) regions of the earth. Spruces are large trees, from 20–60 (–95) m tall when mature, and can be distinguished by their whorled branches and conical form. The needles, or leaves, of spruce trees are attached singly to the branches in a spiral fashion, each needle on a small peg-like structure called a pulvinus. The needles are shed when 4–10 years old, leaving the branches rough with the retained pulvinus (an easy means of distinguishing them from other similar genera, where the branches are fairly smooth).

Spruces are used as food plants by the larvae of some Lepidoptera species; see list of Lepidoptera that feed on spruces. They are also used by the larvae of Gall Adelgids (Adelges species).

The word "spruce" derives from an obsolete term for Prussia in Polish ("z Prus")

Scientists have found a cluster of Norway Spruce in the mountains in western Sweden, nicknamed Old Tjikko, which at an age of 9,550 years are claimed to be the world's oldest known living trees. However, this is not an age of an individual trunk but of the clone, and Pando, a clone of 47,000 Quaking Aspens, is estimated to be between 80,000 and one million years old.

Classification

DNA analysesRan, J.-H., Wei, X.-X. & Wang, X.-Q. 2006. Molecular phylogeny and biogeography of Picea (Pinaceae): Implications for phylogeographical studies using cytoplasmic haplotypes. Mol Phylogenet Evol. 41(2): 405-19.Sigurgeirsson, A. & Szmidt, A.E. 1993. Phylogenetic and biogeographic implications of chloroplast DNA variation in Picea. Nordic Journal of Botany 13(3): 233-246. have shown that traditional classifications based on the morphology of needle and cone are artificial. A recent study found that P. breweriana had a basal position, followed by P. sitchensis, and the other species were further divided into three clades, suggesting that Picea originated in North America: