Spruce

This article is about the tree. For other uses, see Spruce (disambiguation).

A spruce is a tree of the genus Picea (/paɪˈsiː.ə/),^[1] 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.

Spruce Temporal range: Valanginian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Picea abies, Norway spruce
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Pinaceae
Subfamily:	Piceoideae Frankis
Genus:	Picea Dietrich
Type species
Picea abies (L.) H. Karst.
Species
About 37; see text.
Synonyms
Veitchia Lindley

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.

Etymology

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".^[2][3]

Description

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.^[4]

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.^[5]

Picea abies botany. 1:young female cone; 2:male cones; 3:mature female cone; 4:pulvinus at leaf base; 5:squarish cross-section of leaf; 6:top of scale; 7:underside of scale; 10:winged seed

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.^[6][7][8] Picea glauca and Picea engelmannii, for instance, do differ in flower, shoot and needle characteristics, "but those in the cone are most easily assessed".^[9][10][11]

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.^[12]

• 
  Leaf arrangement. Picea abies
• 
  The squarish needle has a peg-like base, the pulvinus. Picea abies
• 
  Pulvini remain after the needles fall. Picea glauca
• 
  Young female cone of Picea abies, bracts visible
• 
  Resinous mature female cone of Picea engelmannii, bracts no longer visible

Evolution

Fossil history

Further information: List of fossil Picea species

Fossilised winged seeds of Picea ugoana. Early Miocene, Niigata Prefecture, Japan

The Picea lineage begins in the fossil record some 130 million years ago (mya). The only surviving branch of that lineage, however, diverged only around 30 mya, meaning that the rest of the crown group has no living descendants. That, in turn, means that the biogeography and ecology of the crown group cannot be inferred from living members of the genus.^[13] For example, middle Eocene spruce fossils have been found in the Buchanan Lake Formation of Canada (46.2–40.4 mya).^[14]

External phylogeny

Based on transcriptome analysis, Picea is most closely related to the genus Cathaya; those form a clade, sister to the genus Pinus. These genera, with firs and larches, form the pinoid clade of the Pinaceae.^[15]

Pinaceae	Abietoideae (firs, cedars, hemlocks) Pinoideae Lariceae Pseudotsuga (Douglas firs) Larix (larches) Pineae Cathaya (1 sp.) Picea (spruces) Pinus (pines)

Internal phylogeny

DNA analyses have shown that traditional classifications based on the morphology of needle and cone are artificial.^[16][17] A 2006 study found that P. breweriana had a basal position, followed by P. sitchensis,^[16] and the other species were further divided into three clades, suggesting that Picea originated in North America. The oldest record of spruce that has been found in the fossil record is from the Early Cretaceous (Valanginian) of western Canada, around 136 million years old.^[18]

A phylogeny of the genus is shown in the cladogram.^[19][20]

Picea

section P. sitchensis (Bongard) Carrière Sitcha section P. breweriana Watson Brewerianae section series P. likiangensis (Franchet) Pritzel P. farreri Page & Rushforth P. spinulosa (Griffith) Henry Likiangenses series P. schrenkiana Fischer & Meyer Schrenkianae series P. smithiana (Wallich) Boiss. P. glauca (Moench) Voss P. engelmannii Parry ex Engelmann Glaucae series P. martinezii T.F.Patt. P. chihuahuana Martínez P. alcoquiana (Veitch ex Lindley) Carrière P. brachytyla (Franchet) Pritzel P. neoveitchii Masters P. morrisonicola Hayata P. purpurea Masters P. wilsonii Masters P. orientalis (von Linné) Peterm. P. maximowiczii Regel ex Masters P. polita (Siebold & Zuccarini) Carrière Orientales Casicta section series P. pungens Engelmann Pungentes series P. glehnii (Schmidt) Masters P. jezoensis (Sieb. & Zuccarini) Carrière P. rubens Sargent P. mariana (Miller) Britton, Sterns & Poggenburg P. omorika (Pančić) Purkyne Jezoenses series P. obovata Ledeb. P. abies (von Linné) Karsten P. koyamae Shiras. P. asperata Masters P. koraiensis Nakai P. torano (Siebold ex Koch) Koehne P. retroflexa Masters P. shirasawae Hayashi P. crassifolia Komarov P. meyeri Rehder & Wilson Abies Picea

Taxonomy

Taxonomic history

In 1824, Albert Dietrich set up the genus Picea. In 1887, the German botanist Heinrich Moritz Willkomm revised the genus using vegetative characteristics of the trees, rather than of the cones. His classification was followed in 1890 by that of the German botanist Heinrich Mayr, and again in 1982 by that of the Taiwanese biologist Leroy Liu on a similar basis.^[5] Only in 1989 did Peter A. Schmidt classify the species in the genus using mainly seed cone characteristics.^[5][21]

Species

As of September 2025^[update], Plants of the World Online accepted 37 species.^[22] The grouping is based on Ran et al. (2006).^[16]

Basal species

• Picea breweriana – Brewer's spruce, Klamath Mountains, North America; local endemic
• Picea sitchensis – Sitka spruce, Pacific coast of North America; the largest species, to 95 m tall; important in forestry

Clade I (northern and western North America, in boreal forests or high mountains)

• Picea engelmannii – Engelmann spruce, western North American mountains; important in forestry
• Picea glauca, syn. Picea laxa – white spruce, northern North America; important in forestry

Clade II (throughout Asia, mostly in mountainous areas, a few isolated populations in higher elevations of Mexico)

• Picea brachytyla – Sargent's spruce, southwest China
• Picea chihuahuana – Chihuahua spruce, northwest Mexico (rare)
• Picea farreri – Burmese spruce, northeast Burma, southwest China (mountains)
• Picea likiangensis – Likiang spruce, southwest China
• Picea martinezii – Martinez spruce, northeast Mexico (very rare, endangered)
• Picea maximowiczii – Maximowicz spruce, Japan (rare, mountains)
• Picea morrisonicola – Taiwan spruce, Taiwan (high mountains)
• Picea neoveitchii – Veitch's spruce, northwest China (rare, endangered)
• Picea orientalis – Caucasian spruce or Oriental spruce, Caucasus, northeast Turkey
• Picea polita, syn. Picea torano – tiger-tail spruce, Japan
• Picea purpurea – purple cone spruce, western China
• Picea schrenkiana – Schrenk's spruce, mountains of central Asia
• Picea smithiana – morinda spruce, western Himalaya, eastern Afghanistan, northern and northwest India
• Picea spinulosa – Sikkim spruce, northeast India (Sikkim), eastern Himalaya
• Picea wilsonii – Wilson's spruce, western China

Clade III (Europe, Asia, and North America, mostly in boreal forests or mountainous areas)

• Picea abies – Norway spruce, Europe; important in forestry, the original Christmas tree
• Picea alcoquiana – ("P. bicolor") Alcock's spruce, central Japan (mountains)
• Picea asperata – dragon spruce, western China; several varieties
• Picea crassifolia – Qinghai spruce, China
• Picea glehnii – Glehn's spruce, northern Japan, Sakhalin
• Picea jezoensis – Jezo spruce, northeast Asia, Kamchatka south to Japan
• Picea koraiensis – Korean spruce, Korea, northeast China
• Picea koyamae – Koyama's spruce, Japan (mountains)
• Picea mariana – black spruce, northern North America
• Picea meyeri – Meyer's spruce, northern China (from Inner Mongolia to Gansu)
• Picea obovata – Siberian spruce, north Scandinavia, Siberia; often treated as a variant of P. abies (and hybridises with it), but has distinct cones
• Picea omorika – Serbian spruce, Serbia and Bosnia; local endemic; important in horticulture
• Picea pungens – blue spruce or Colorado spruce, Rocky Mountains, North America; important in horticulture
• Picea retroflexa – green dragon spruce, China
• Picea rubens – red spruce, northeastern North America; important in forestry, known as Adirondack in musical-instrument making

Others

• Picea aurantiaca Mast.
• Picea austropanlanica Silba
• Picea linzhiensis (W.C.Cheng & L.K.Fu) Rushforth

Hybrids

• Picea × albertiana S.Br.
• Picea × fennica (Regel) Kom.
• Picea × lutzii Little
• Picea × notha Rehder

Genome

The nuclear,^[23] mitochondrial^[24][25] and chloroplast^[26] genomes of British Columbia interior spruce have been sequenced. The large (20 Gbp) nuclear genome and associated gene annotations of interior spruce (genotype PG29) were published in 2013^[27] and 2015.^[28]

Ecology

Establishment

Spruce seedlings are most vulnerable from germination to the following spring. More than half of spruce seedling mortality probably occurs during the first growing season and remains high during the first winter.^[29] Seedlings four to five years old can be considered "established", since only unusual factors such as snow mold, fire, trampling, or predation can then impair regeneration success.^[30] In dry habitats, seedlings can be considered established when three years old.^[31]

Distribution and habitat

Like firs and pines, spruces are important both ecologically and economically in the Northern Hemisphere. While some species are widespread, most have limited geographical ranges. Like firs but unlike pines, spruces are mainly confined to colder areas, with many species in the west of China. The spruces are less tolerant of heat than the firs, and accordingly their distribution reaches further north and less far south.^[5]

Diseases

Sirococcus blight is caused by the deuteromycete fungus Sirococcus tsugae. It affects spruces across the Northern Hemisphere, both in forests and in nurseries, causing severe defoliation and shoot blight. It first appeared in Germany and the United Kingdom in 2014. It is spread when rain splashes on the asexual conidia. Control is limited to biosecurity measures.^[32]

Rhizosphaera needle cast, a disease that causes leaf fall, is caused by the infection of spruces by the ascomycete fungus Rhizosphaera in North America. It causes severe defoliation. Dead needles show rows of black fruiting bodies. Infection is mainly on lower branches. Control is possible with the fungicide Chlorothalonil, which prevents new infection, if all needles can be sprayed.^[33]

Canker disease of spruce is caused by the ascomycete fungal pathogen Leucostoma kunzei (also called Cytospora and Valsa). It is dispersed by spores from pycnidia within the tree's bark, which contain asexual conidia. The conidia are spread by rain splash. The disease affects all spruce species. Trees are more vulnerable under water stress. Fungicides containing copper prevent new infection but these are readily washed off by rain and are not suitable for forestry use.^[34]

Predators

Small mammals ingest conifer seeds, and consume seedlings.^[35] The short-tailed meadow vole (Microtus pennsylvanicus Ord) voraciously eats white spruce and lodgepole pine seedlings, pulling them out of the ground and consuming them whole.^[35] The impact varies; in western Montana, spruce seedling success was little better on protected than on unprotected seed spots,^[36] but in British Columbia, spruce regeneration depends on protection from rodents.^[37] A mouse can eat 2000 white spruce seeds per night.^[38] Seed losses can be large: repeated applications of half a million white spruce seeds per hectare in Alberta failed to produce the required 750 trees per hectare.^[39]

Larger mammals too can have an impact; as much as 90% of a cone crop can be harvested by red squirrels,^[40] while bark-stripping of white spruce by black bears is locally important in Alaska.^[41]

Pests

Gallery of the European spruce bark beetle (Ips typographus) in the inner bark (phloem).

The European spruce bark beetle (Ips typographus, also called the eight-toothed spruce bark beetle) lays its eggs in the inner bark (phloem) of Picea abies, other spruces, and sometimes other conifers across Europe and Asia. They bring with them ophiostomatoid fungi, some of them serious tree pathogens.^[42] The larvae make tunnels in the phloem; in large numbers, they can cut off the phloem and kill the tree.^[43]

The eastern spruce budworm (Choristoneura fumiferana) is a major pest of spruce trees in forests throughout Canada and the eastern United States.^[44] Two of the main host plants are black spruce and white spruce.^[45] Population levels oscillate, sometimes reaching extreme outbreak levels that can cause extreme defoliation of and damage to spruce trees. To reduce destruction, there are multiple methods of control in place, including pesticides.^[46]

The great spruce bark beetle (Dendroctonus rufipennis) is a destructive pest of spruce forests in western North America,^[47] and has become widespread in Europe and Asia. It arrived in the United Kingdom sometime between 1973 and 1982. It causes dieback of spruce, worst when the trees are stressed by drought. Continued attack can kill the trees. The pest is subject to effective biological control by a natural predator, the Siberian beetle Rhizolophus grandis.^[48]

Uses

Timber

Wood of Norway spruce

Spruce is useful as a building wood, known by names such as North American timber, SPF (spruce, pine, fir) and whitewood.^[49] It is commonly used in Canadian Lumber Standard (CLS) graded wood.^[50] Spruce wood is used for many purposes, ranging from general construction work and crates to highly specialised uses in wooden aircraft.^[51] The Wright brothers' first aircraft, the Flyer, was built of spruce,^[52] but the 1947 Hughes H-4 Hercules flying boat, known as the "Spruce Goose", was, in fact, mainly made of birch.^[53]

Because this species has poor resistance to insects and fungi after logging, it is recommended for indoor construction, such as indoor drywall framing. Spruce wood left outside cannot be expected to last more than 12–18 months depending on the climate.^[54]

Tonewood

A lute with a spruce soundboard

Spruce is the standard material used in soundboards for stringed instruments, including guitars. Wood used for this purpose is called tonewood. Species used include Engelmann spruce in North America, and Sitka spruce in Europe.^[55] In the Dolomites, the Norway spruces of the Paneveggio "Violins Forest" have for centuries been used for making musical instruments, supposedly including by the leading violin-maker Antonio Stradivari.^[56]

Paper

Spruce is a good pulpwood, as it has long fibres which bind together to make strong paper,^[57] especially from trees over 60 years old. The pulp, known as northern bleached softwood kraft (NBSK), is used to make products such as tissue paper.^[58]

Other materials

A spruce root basket woven by Tlingit people, Alaska

The resin was used in the manufacture of pitch in the past (before the use of petrochemicals); the scientific name Picea derives from Latin picea "pitch pine" (the Scots pine).^[59] Native Americans use the thin, pliable roots of some species for weaving baskets^[60][61] and for sewing together pieces of birch bark for canoes.^[62] Kiidk'yaas, felled in 1997, was a golden Sitka Spruce sacred to the Haida people.^[63] Spruces are popular ornamental trees.^[64] Picea abies is extensively used as Christmas trees.^[65] Spruce branches are used at Aintree Racecourse in Liverpool to build fences used as horse jumps on the Grand National course.^[66]

Food and drink

The fresh shoots of many spruces are a natural source of vitamin C.^[67] Captain Cook made alcoholic sugar-based spruce beer during his sea voyages in order to prevent scurvy in his crew.^[68][69]

In Finland, young spruce buds are sometimes used as a spice, or boiled with sugar to create spruce bud syrup.^[70][71]

In art

Around 1900, Edvard Munch made numerous oil paintings of spruce forests, now in the Munch Museum in Oslo.^[72] The Finnish artist and photographer Eija-Liisa Ahtila's work Horizontal–Vaakasuora, exhibited from 2012 at Stockholm's Moderna Museet and the Shirley Sherwood Gallery depicts a 30-metre-tall spruce, arranged horizontally, in six large video panels.^[73][74] XIBT magazine described it as "delving into notions of ecology and symbiosis as well as the essence of existentialism within the context of our external world."^[75]

• 
  Augustin Hirschvogel, River Landscape with Five Bare Spruce Trees, etching, 1549
• 
  Joachim Frich, Study of a Spruce, oil on board, 1851
• 
  Werner Holmberg, Spruce Saplings in Sandy Soil, Study, 1854
• 
  Carl Fredrik Hill, The Black Spruces, oil on canvas, 1878
• 
  Edvard Munch, Dark Spruce Forest, oil on canvas, 1899
• 
  Abby Williams Hill, Basaltic Rocks, oil on canvas, 1904
• 
  Tom Thomson, Black Spruce and Maple, oil on wood panel, 1915