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.
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.
- 1c Cones with smoothly rounded scales; leaves viciously sharp-pointed
- * Picea maximowiczii Maximowicz Spruce. Japan (rare, mountains).
- * Picea torano Tiger-tail Spruce. Japan.
- * Picea neoveitchii Veitch's Spruce. Northwest China (rare, endangered).
- * Picea martinezii Martinez Spruce. Northeast Mexico (very rare, endangered).
- * Picea chihuahuana Chihuahua Spruce. Northwest Mexico (rare).
2 Cones with thickish wavy scales, leaves slightly to strongly flattened: section Omorika
- 2a Cones mostly with rounded scales; leaves flattened in section, white below
- * Picea breweriana Brewer's Spruce. Klamath Mountains, North America; local endemic.
- * Picea brachytyla Sargent's Spruce. Southwest China.
- * Picea farreri Burmese Spruce. Northeast Burma, southwest China (mountains).
- * Picea omorika Serbian Spruce. Serbia; local endemic; important in horticulture.
- 2b Cones mostly with wavy scales; leaves slightly flattened in section, often paler below
- * Picea mariana Black Spruce. Northern North America.
- * Picea rubens Red Spruce. Northeastern North America; important in forestry.
- * Picea glehnii Glehn's Spruce. Northern Japan, Sakhalin.
- * Picea alcockiana ("P. bicolor") Alcock's Spruce. Central Japan (mountains).
- * Picea purpurea Purple Spruce. Western China.
- * Picea balfouriana Balfour's Spruce. Western China.
- * Picea likiangensis Likiang Spruce. Southwest China.
- * Picea spinulosa Sikkim Spruce. Eastern Himalaya.
3 Cones with very thin, wavy scales: section 'Casicta'
- * Picea glauca White Spruce. Northern North America; important in forestry.
- * Picea engelmannii Engelmann Spruce. Western North American mountains; important in forestry.
- * Picea sitchensis Sitka Spruce. Pacific Coast of North America; the largest species, to 95m tall; important in forestry.
- * Picea jezoensis Jezo Spruce. Northeast Asia, Kamchatka south to Japan.
- * Picea pungens Blue Spruce or Colorado Spruce. Rocky Mountains, North America; important in horticulture.
Spruce is one of the most important woods for paper
manufacture, as it has long wood fibres which bind together to make strong paper. Spruces are cultivated over vast areas for this purpose.
Spruces are also popular ornamental trees in horticulture, admired for their evergreen, symmetrical narrow-conic growth habit. For the same reason, some (particularly Picea abies and P. omorika) are also extensively used as Christmas trees.
Spruce wood, often called whitewood, is used for many purposes, ranging from general construction work and crates to highly specialised uses in wooden aircraft and many musical instruments, including guitars, mandolins, cellos, violins, and the soundboard at the heart of a piano. The Wright Brothers first aircraft was built of spruce.
The resin was used in the manufacture of pitch in the past (before the use of petrochemicals); the scientific name Picea is generally thought to be derived from Latin pix, pitch (though other etymologies have been suggested).
The leaves and branches, or the essential oils, can be used to brew spruce beer. The tips from the needles can be used to make spruce tip syrup.
Native Americans in eastern North America once used the thin, pliable roots of some species for weaving baskets and for sewing together pieces of birch bark for canoes. See also Kiidk'yaas for an unusual golden Sitka Spruce sacred to the Haida people. Native Americans in New England also used the sap to make a gum which was used for various reasons.
In survival situations spruce needles can be directly ingested or boiled into a tea. This replaces large amounts of vitamin C. Also, water is stored in a spruce's needles, providing an alternative means of hydration. Spruce can be used as a preventative measure for scurvy in an environment where meat is the only prominent food source.
Spruce branches are also used at Aintree racecourse, Liverpool, to build several of the fences on the Grand National course.