Spruce

A spruce is a tree of the genus Picea (/paɪˈsiː.ə/), a genus of some 37 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Northern Hemisphere. Picea is the sole genus in the subfamily Piceoideae.

Spruces can be distinguished from other genera of the family Pinaceae by their needles (leaves), which are four-sided and attached singly to small persistent peg-like structures (pulvini) on the twigs. The needles are shed when 4–10 years old, leaving the twigs rough with the retained pegs. Pests of spruce forestry include the eastern spruce budworm, the European spruce bark beetle, and the great spruce bark beetle.

Spruce is a major producer of timber for construction, and of pulp for paper. It is the standard material for the soundboards of stringed instruments. Native Americans use the roots of some species for weaving baskets. The Norway spruce is widely used for Christmas trees. Artists including Augustin Hirschvogel in the 16th century, Edvard Munch around 1900, and Eija-Liisa Ahtila in the 21st century have depicted spruces in etchings, oil paintings, and video installations.

Spruce, from Middle English spruse or Sprws appears originally to have denoted goods, including wooden objects, imported from Prussia. The Middle English word is in turn from Old French Pruce, "Prussia".

Spruces differ from other Pinaceae in two distinctive characters. Firstly, they have evergreen needle leaves that are more or less square in cross-section. Secondly, they have a pulvinus (plural pulvini), a small peg-like structure at the base of each needle, that remains when the needle falls. Needles stay on the tree for between four and ten years.

The tree has a straight trunk. It is resinous and monoecious, with separate male and female cones on the same tree. Young trees have a pyramidal crown; in older trees, this tends to become a roughly cylindrical column. Branches grow from the trunk in regular whorls; lower branches are mostly soon lost. Young branches rise above the horizontal, but older branches do not. The cones have leaflike bracts that appear at the time of pollination, but unlike Abies (fir cones) these are later covered by the seed scales. Each seed sits with its lower half in a cup on the seed scale; the seeds have a large wing.

The structure of the cone scales, including length, width, and how much of the scale is free, is the most useful feature for telling species of spruce apart. Picea glauca and Picea engelmannii, for instance, do differ in flower, shoot and needle characteristics, "but those in the cone are most easily assessed".

Spruce may be one of the longest-living trees. In the mountains of Dalarna, Sweden, a Norway spruce nicknamed Old Tjikko has reproduced by layering, reaching an age of 9,550 years; it is claimed to be the world's oldest known living tree.