Spruce refers to trees 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 sterigmata. The needles are shed when 4–10 years old, leaving the branches rough with the retained sterigmata (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 as food plants by Gall Adelgids (Adelges species).

The word "spruce" derives from an obsolete term for Prussia.

Scientists have found a cluster of Norway Spruce in the mountains in western Sweden which, at an age of 9,550 years, is the world's oldest known living trees.

Classification

1 Cones with thickish scales; leaves quadrangular in cross-section: section Picea

1a Cones with (mostly) pointed scales; leaves blunt or somewhat pointed

• Picea abies Norway Spruce. Europe; important in forestry. The original Christmas tree.
• Picea asperata Dragon Spruce. Western China; several varieties.
• Picea meyeri Meyer's Spruce.

1b Cones with smoothly rounded scales; leaves blunt or somewhat pointed

• Picea orientalis Caucasian Spruce or Oriental Spruce . Caucasus, northeast Turkey.
• Picea morrisonicola Yushan Spruce . Taiwan (high mountains).
• Picea wilsonii Wilson's Spruce . Western China.
• Picea obovata Siberian Spruce. North Scandinavia, Siberia. Often treated as a variant of P. abies (and hybridises with it) but distinct cones.
• Picea schrenkiana Schrenk's Spruce. Mountains of central Asia.
• Picea smithiana Morinda Spruce. Western Himalaya.
• Picea alpestris Norway Spruce, Alpine Spruce. The Alps in Europe; rare, often treated as a variant of P. abies (and hybridises with it) distinct cones.