Picea is the name of a genus of coniferous evergreen trees that are more commonly known as spruce trees. They are part of the pine family, Pinacea, which includes 35 distinct species, such as the white spruce, Picea glauca ; the red spruce, Picea rubens ; and the blue spruce, Picea pungens. Its members can be found across the northern hemisphere, from North America to Europe and Asia, and are some of the most abundant species in many parts of Canada, Scandinavia, Russia and parts of the United States. These trees do not grow naturally in the southern hemisphere.
Members of the Picea genus vary in size but generally grow to 65-200 feet (about 20-60 m) tall. The tallest species, the Sitka spruce, Picea sitchensis, sometimes reaching about 250 feet (about 75 m). The bark of these trees can range from gray to reddish-brown, depending on species, and is generally thin, becoming somewhat scaly as the tree ages. Branches grow mostly in a whorled pattern and taper conically toward the apex of the trunk.
The leaves, or needles, of these trees generally are less than 1 inch (2.5 cm) in length and grow singly, emanating from the branch in a spiral pattern. Like all coniferous trees, Picea bear seed cones in the spring. These might be green to purple in color but fade to brown as autumn approaches. These trees can live very long lives; the oldest recorded specimen is an Engelmann spruce, or Picea engelmannii, that has reached an age of more than 850 years.
The Picea genus is important in modern industry and is used extensively in the making of paper, as well as in other more specialized products such as musical instruments. It also is commonly used as building wood, though typically for indoor building only, because spruce wood quickly decays outdoors after it has been logged. Owing to its wide commercial use, the Picea genus is a staple of the forestry industry, with the Sitka spruce and the Norway spruce, Picea abies, being two of the most commonly logged species.
Spruces also remain popular trees in horticulture. They are commonly used as rock garden plants or in hedgerows. Several species, including the Serbian spruce, Picea omorika; the black spruce, Picea mariana; and the Norway spruce are also popular for their use as Christmas trees.