|Norway Spruce (Picea abies)|
About 35; see text.
A spruce is a tree 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 about 20-60 metres (about 60-200 feet) 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 pulvinus. The needles are shed when 4–10 years old, leaving the branches rough with the retained pulvinus (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 (moth and butterfly) species; see list of Lepidoptera that feed on spruces. They are also used by the larvae of gall adelgids (Adelges species).
In the mountains of western Sweden scientists have found a Norway Spruce tree, nicknamed Old Tjikko, which by reproducing through layering has reached an age of 9,550 years and is claimed to be the world's oldest known living tree.
- 1 Classification
- 2 Growth
- 3 Nomenclature
- 4 Uses
- 5 Diseases
- 6 Predators
- 7 Etymology
- 8 Comparison Chart
- 9 References
- 10 External links
DNA analyses have shown that traditional classifications based on the morphology of needle and cone are artificial. A recent study found that P. breweriana had a basal position, followed by P. sitchensis, and the other species were further divided into three clades, suggesting that Picea originated in North America.
There are thirty-five named species of spruce in the world.
- Clade I
- Clade II
- 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 purpurea – Purple 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 torano – Tiger-tail Spruce, Japan
- Picea wilsonii – Wilson's Spruce, western China
- Clade III
- Picea abies – Norway Spruce, Europe; important in forestry, the original Christmas tree
- Picea alcoquiana – ("P. bicolor") Alcock's Spruce, central Japan (mountains)
- 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
- Picea asperata – Dragon Spruce, western China; several varieties
- Picea crassifolia – 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 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
Determining that a tree is a member of a spruce species is not difficult; evergreen needles that are more or less 4-angled, and especially the pulvinus, give it away. But beyond that, determination can become more difficult. Intensive sampling in the Smithers/Hazelton/Houston area of British Columbia showed Douglas (1975), according to Coates et al. (1994), that cone scale morphology was the feature most useful in differentiating species of spruce; the length, width, length: width ratio, the length of free scale (the distance from the imprint of the seed wing to the tip of the scale), and the percentage free scale (length of free scale as a percentage of the total length of the scale) were most useful in this regard. Daubenmire (1974), after range-wide sampling, had already recognized the importance of the 2 latter characters. Taylor (1959) had noted that the most obvious morphological difference between typical Picea glauca and typical P. engelmannii was the cone scale, and Horton (1956,1959) found that the most useful diagnostic features of the 2 spruces are in the cone; differences occur in the flower, shoot and needle, “but those in the cone are most easily assessed” (Horton 1959). Coupé et al. (1982) recommended that cone scale characters be based on samples taken from the mid-section of each of 10 cones from each of 5 trees in the population of interest.
Without cones, morphological differentiation among spruce species and their hybrids is more difficult. Species classification for seeds collected from spruce stands in which introgressive hybridization between white and Sitka spruces (Picea sitchensis) may have occurred is important for determining appropriate cultural regimes in the nursery. If, for instance, white spruce grown at container nurseries in southwestern British Columbia are not given an extended photoperiod, leader growth ceases early in the first growing season, and seedlings do not reach the minimum height specifications (Arnott 1974, 1979). But, if an extended photoperiod is provided for Sitka spruce, seedlings become unacceptably tall by the end of the first growing season (Arnott, unpublished data, cited by Yeh and Arnott 1986). Species classification of seedlots collected in areas where hybridization of white and Sitka spruces has been reported has depended on (i) easily measured cone scale characters of seed trees, especially free scale length, (ii) visual judgements of morphological characters, e.g., growth rhythm, shoot and root weight, and needle serration, or (iii) some combination of (i) and (ii) (Yeh and Arnott 1986). Useful to a degree, these classification procedures have important limitations; genetic composition of the seeds produced by a stand is determined by both the seed trees and the pollen parents, and species classification of hybrid seedlots and estimates of their level of introgression on the basis of seed-tree characteristics can be unreliable when hybrid seedlots vary in their introgressiveness in consequence of spatial and temporal variations in contributions from the pollen parent (Yeh and Arnott 1986). Secondly, morphological characters are markedly influenced by ontogenetic and environmental influences, so that to discern spruce hybrid seedlot composition with accuracy, hybrid seedlots must differ substantially in morphology from both parent species. Yeh and Arnott (1986) pointed out the difficulties of estimating accurately the degree of introgression between white and Sitka spruces; introgression may have occurred at low levels, and/or hybrid seed lots may vary in their degree of introgression in consequence of repeated backcrossing with parental species.
Spruce seedlings are most susceptible immediately following germination, and remain highly susceptible through to the following spring. More than half of spruce seedling mortality probably occurs during the first growing season and is also very high during the first winter (Alexander 1987), when seedlings are subjected to freezing damage, frost heaving and erosion, as well as smothering by litter and snow-pressed vegetation. Seedlings that germinate late in the growing season are particularly vulnerable because they are tiny and have not had time to harden off fully.
Mortality rates generally decrease sharply thereafter, but losses often remain high for some years. “Establishment” is a subjective concept based on the idea that once a seedling has successfully reached a certain size, not much is likely to prevent its further development. Criteria vary, of course, but Noble and Ronco (1978), for instance, considered that seedlings 4 to 5 years old, or 8 cm to 10 cm tall, warranted the designation “established”, since only unusual factors such as snow mold, fire, trampling, or predation would then impair regeneration success. Eis (1967) suggested that in dry habitats on either mineral soil or litter seedbeds a 3-year-old seedling may be considered established; in moist habitats, seedlings may need 4 or 5 years to become established on mineral soil, possibly longer on litter seedbeds.
Growth remains very slow for several to many years. Three years after shelterwood felling in subalpine Alberta, dominant regeneration averaged 5.5 cm in height in scarified blocks, and 7.3 cm in non-scarified blocks (Day 1970), possibly reflecting diminished fertility with the removal of the A horizon.
|This section requires expansion. (June 2009)|
|This section needs additional citations for verification. (June 2009)|
Spruce is useful as a building wood, commonly referred to by several different names including North American timber, SPF (spruce, pine, fir) and whitewood. Spruce wood is used for many purposes, ranging from general construction work and crates to highly specialised uses in wooden aircraft. The Wright brothers' first aircraft, the Flyer, was built of spruce.
Because this species has no insect or decay resistance qualities after logging, it is generally recommended for construction purposes as indoor use only (ex. indoor drywall framing). Spruce wood, when left outside cannot be expected to last more than 12–18 months depending on the type of climate it is exposed to.
Spruce is one of the most important woods for paper uses, as it has long wood fibres which bind together to make strong paper. The fibres are thin walled and collapse to thin bands upon drying. Spruces are commonly used in mechanical pulping as they are easily bleached. Together with northern pines, northern spruces are commonly used to make NBSK. Spruces are cultivated over vast areas as pulpwood.
Food and medicine
The fresh shoots of many spruces and pines are a natural source of vitamin C. Captain Cook made alcoholic sugar-based spruce beer during his sea voyages in order to prevent scurvy in his crew. 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 [clarification needed]. 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 [clarification needed]. Spruce can be used as a preventive measure for scurvy in an environment where meat is the only prominent food source [clarification needed].
Spruce is the standard material used in soundboards for many musical instruments, including guitars, mandolins, cellos, violins, and the soundboard at the heart of a piano and the harp. Wood used for this purpose is referred to as tonewood.
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).
Native Americans in North America use 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.
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 branches are also used at Aintree racecourse, Liverpool, to build several of the fences on the Grand National course. It is also used to make sculptures and Christmas trees.
Sirococcus conigenus blight (Deuteromycotina, Coelomtcetes)
Sirococcus conigenus causes shoot blight and seedling mortality of conifers in North America, Europe, and North Africa. Under its former name, Ascochyta piniperda, twig blight damage to seedlings of white and red spruces in a nursery near Asheville, North Carolina, were reported by Graves (1914). Hosts include white, black, [[Picea engelmannii |Engelmann]], Norway, and red spruces, although they are not the plants most commonly damaged. Sirococcus blight of spruces in nurseries show up randomly in seedlings to which the fungus was transmitted in infested seed. First-year seedlings are often killed, and larger plants may become too deformed for planting. Outbreaks involving < 30% of spruce seedlings in seedbeds have been traced to seed lots in which only 0.1% to 3% of seeds were infested. Seed infestation has in turn been traced to the colonization of spruce cones by S. conigenus in forests of the western interior. Infection develops readily if conidia are deposited on succulent plant parts that remain wet for at least 24 hours at 10°C to 25°C. Longer periods of wetness favour increasingly severe disease. Twig tips killed during growth the previous year shows a characteristic crook.
Rhizosphaera kalkhoffi needle cast
Rhizosphaera infects white spruce, blue spruce (Picea pungens), and Norway spruces throughout Ontario, causing severe defoliation and sometimes killing small, stressed trees. White spruce is intermediately susceptible. Dead needles show rows of black fruiting bodies. Infection usually begins on lower branches. On white spruce, infected needles are usually retained on the tree into the following summer. The fungicide Chlorthalonil is registered for controlling this needle cast (Davis 1997).
Valsa kunzei branch and stem canker
A branch and stem canker associated with the fungus Valsa kunzei Fr. var. picea was reported on white and Norway spruces in Ontario (Jorgensen and Cafley 1961) and Quebec (Ouellette and Bard 1962). In Ontario, only trees of low vigour were affected, but in Quebec vigorous trees were also infected.
Small mammals consume conifer seeds, and also eat seedlings. Cage feeding of deer mice (Peromyscus maniculatus) and red-backed vole (Myodes gapperi) showed a daily maximum seed consumption of 2000 white spruce seeds and of 1000 seeds of lodgepole pine, with the 2 species of mice consuming equal amounts of seed, but showing a preference for the pine over the spruce (Wagg 1963). The short-tailed meadow vole (Microtus pennsylvanicus Ord) voraciously ate all available white spruce and lodgepole pine seedlings, pulling them out of the ground and holding them between their front feet until the whole seedling had been consumed. Wagg (1963) attributed damage observed to the bark and cambium at ground level of small white spruce seedlings over several seasons to meadow voles.
Once shed, seeds contribute to the diet of small mammals, e.g., deer mice, red-backed voles, mountain voles (Microtus montanus), and chipmunks (Eutamias minimus). The magnitude of the loss is difficult to determine, and studies with and without seed protection have yielded conflicting results. In western Montana, for example, spruce seedling success was little better on protected than on unprotected seed spots (Schopmeyer and Helmers 1947), but in British Columbia spruce regeneration depended on protection from rodents (Smith 1955).
An important albeit indirect biotic constraint on spruce establishment is the depredation of seed by squirrels. As much as 90% of a cone crop has been harvested by red squirrels (Zasada et al. 1978). Deer mice, voles, chipmunks, and shrews can consume large quantities of seed; 1 mouse can eat 2000 seeds per night (Radvanyi 1970b). Repeated applications of half a million seeds/ha failed to produce the 750 trees/ha sought by Northwest Pulp and Power, Ltd., near Hinton, Alberta (Radvanyi 1972), but no doubt left a lot of well-fed small mammals. Foraging by squirrels for winter buds (Rowe 1952) has not been reported in relation to young plantations, but Wagg (1963) noted that at Hinton AB, red squirrels were observed cutting the lateral and terminal twigs and feeding on the vegetative and flower buds of white spruce.
Red squirrels in Alaska have harvested as much as 90% of a cone crop (Zasada et al. 1978); their modus operandi is to cut off great numbers of cones with great expedition early in the fall, and then “spend the rest of the fall shelling out the seeds”. In Manitoba, Rowe (1952) ascribed widespread severing of branch tips 5 cm to 10 cm long on white spruce ranging “from sapling to veteran size” to squirrels foraging for winter buds, cone failure having excluded the more usual food source. The damage has not been reported in relation to small trees, outplants or otherwise.
Porcupines (Erethizon dorsatum L.) may damage spruce (Nienstaedt 1957), but prefer red pine (McLeod 1956). Bark-stripping of white spruce by black bear (Euarctos americanus perniger) is locally important in Alaska (Lutz 1951), but the bark of white spruce is not attacked by field mice (Microtus pennsylvanicus Ord) (Littlefield et al. 1946), even in years of heavy infestation.
The word "spruce" entered the English language from Old French Pruce, the name of Prussia. Spruce was a generic term for commodities brought to England by Hanseatic merchants and the tree was believed to have come from Prussia.
This is a Spruce Comparison Chart to help identification, ordered by Needle Length. It is drawn from Wikipedia Pages ('wiki' columns) and the needle lengths given in Collins Tree Guide ("CTG") (Paperback 2006 ISBN 978-0-00-720771-8) which differ slightly from wiki pages but CTG relates to Britain/N Europe.
|Latin||Needle Len mm||(Wiki)||Cone Len cm||(Wiki) Len x Width closed/open cm||English||Page CTG|
|Picea orientalis||6-12||6-8||7||5-9 x 1.5||Oriental Spruce,Caucasian Spruce||108-1|
|Picea maximowiczii||10-13||7||Maximowicz Spruce||108-1b|
|Picea mariana||15||6-15||2-3.5||1.5-4 x 1-2||Black Spruce||104-1|
|Picea glehnii||10-15||6||Sakhalin Spruce,Glehn's Spruce||108-2b|
|Picea jezoensis var. hondoensis||15||5||Hondo Spruce||110-2|
|Picea purpurea||6-15||5||Purple Spruce||110-1b|
|Picea rubens||15||12-15||5||3-5||Red Spruce||104-2|
|Picea likiangensis||16||12||Likiang Spruce||110-1|
|Picea glauca||10-16||12-20||6||3-7 x 1.5/2.5||White Spruce||114-3|
|Picea wilsonii||16||8||Wilson's Spruce||106-1|
|Picea asperata||10-18||10-25||12||6-15 x 2-3||Dragon Spruce||112-3|
|Picea alcoquiana||18||12||Alcock's Spruce||108-2|
|Picea koyamae||18||8-16||10||4-9 x 2||Koyama's Spruce||104-3|
|Picea torano||20||12||12 x 5||Tiger-Tail Spruce||112-2|
|Picea pungens f. glauca||20||30||12||10||Blue Colorado Spruce||114-1|
|Picea brachytyla||20||Sargent's Spruce||110-3|
|Picea engelmannii f. glauca||20||30||4-8 x 1.5/3||Blue Engelmann Spruce||114-2|
|Picea jezoensis||15-20||4-7 x 2/3||Jezo Spruce,Jezo Spruce, Yezo Spruce|
|Picea koraiensis||12-22||4-8 x 2||Korean Spruce|
|Picea omorika||22||10-20||6||4-7||Serbian Spruce||106-3|
|Picea chihuahuana||17-23||7-12 x 3/4-5||Chihuahua Spruce|
|Picea alpestris||15-25||12-24||20||9-17||Norway Spruce,Alpine Spruce||102-1b|
|Picea spinulosa||25||17-32||7-11||6-12 x 2||Sikkim Spruce||112-1|
|Picea obovata||15-25||10-20||5-11||5-10 x 1.5-2||Siberian Spruce||102-2|
|Picea abies||15-25||12-24||20||9-17||Norway Spruce,European Spruce||102-1|
|Picea meyeri||13-25||7-11 x 3||Meyer's Spruce|
|Picea sitchensis||30||15-25||10||6-10 x 2/3||Sitka Spruce||106-2|
|Picea breweriana||30||15-35||11||8-15 x 2/3-4||Brewer Spruce, Brewer's Spruce,Weeping Spruce, Brewer's Weeping Spruce||100-2|
|Picea engelmannii||15-30||4-8 x 1.5/3||Engelmann Spruce,White Spruce,Mountain Spruce, Silver Spruce|
|Picea pungens||30||10||Colorado Spruce, Blue Spruce, Colorado Blue Spruce, Green Spruce White Spruce|
|Picea martinezii||23-35||8-16 x 3/6||Martinez Spruce|
|Picea schrenkiana||35||15-35||14||6-12 x 2/2.5-3.5||Schrenk's Spruce, Asian Spruce||100-1b|
|Picea smithiana||40||30-50||14||9-16 x 3/5-6||Morinda Spruce,Morinda Spruce, West Himalayan Spruce||100-1|
|Picea glauca var. porsildii||Alaska White Spruce|
|Picea bicolor||Alcock's Spruce|
|Picea farreri||Burmese Spruce|
|Picea x lutzii||Lutz's Spruce|
|Picea glauca var. albertiana||Alberta White Spruce|
|Picea glauca var. densata||Black Hills White Spruce|
|Picea glauca var. glauca||White Spruce,Eastern White Spruce|
|Picea neoveitchii||Veitch's Spruce|
|Picea polita : see Picea torano||Tiger-Tail Spruce|
|Picea montigena||Dragon Spruce|
|Picea morrisonicola||Yushan Spruce|
- Sunset Western Garden Book, 1995:606–607
- Swedish Spruce Is World's Oldest Tree: Scientific American Podcast
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- Aðalsteinn Sigurgeirsson & Alfred E. Szmidt (1993). "Phylogenetic and biogeographic implications of chloroplast DNA variation in Picea". Nordic Journal of Botany 13 (3): 233–246. doi:10.1111/j.1756-1051.1993.tb00043.x.
- Douglas, G.W. 1975. Spruce (Picea) hybridization in west-central British Columbia. B.C. Min. For., Forest Science, Smithers BC, unpublished report, cited by Coates et al. 1994. (Cited by Coates et al. 1994, orig. not seen)
- Coates, K.D.; Haeussler, S.; Lindeburgh, S.; Pojar, R.; Stock, A.J. 1994. Ecology and silviculture of interior spruce in British Columbia. Canada/British Columbia Partnership Agreement For. Resour. Devel., Victoria BC, FRDA Rep. 220. 182 p.
- Daubenmire, R. 1974. Taxonomic and ecologic relationships between Picea glauca and Picea engelmannii. Can. J. Bot. 52(7):1545–1560.
- Taylor, T.M.C. 1959. The taxonomic relationship between Picea glauca (Moench) Voss and P. engelmannii Parry. Madrono 15(4):111–115. (Cited in Coates et al. 1994).
- Horton, K.W. 1956. A taxonomic and ecological study of Picea glauca and Picea engelmannii in North America. Diploma thesis, Oxford Univ., U.K. 103 p.
- Horton, K.W. 1959. Characteristics of subalpine spruce in Alberta. Can. Dep. Northern Affairs National Resour., For. Branch, For. Res. Div., Ottawa ON, Tech. Note 76. 20 p.
- Coupé, R.; Ray, C.A.; Comeau, A.; Ketcheson, M.V.; Annas, R.M. 1982. A guide to some common plants of the Skeena area, British Columbia. B.C. Min. For., Res. Branch, Victoria BC.
- Arnott, J.T. 1974. Germination and seedling establishment. p. 55–66 in Cayford, J.H. (Ed.). Direct Seeding Symposium, Timmins ON, Sept. 1973, Can. Dep. Environ., Can. For. Serv., Ottawa ON, Proc., Publ. 1339.
- Arnott, J.T. 1979. Effect of light intensity during extended photoperiod on growth of amabalis fir, mountain hemlock, and white and Engelmann spruce seedlings. Can. J. For. Res. 9:82–89.
- Yeh, F.C.; Arnott, J.T. 1986. Electrophoretic and morphological differentiation of Picea sitchensis, Picea glauca, and their hybrids. Can. J. For. Res. 16(4):791–798.
- Alexander, R.R. 1987. Ecology, silviculture, and management of the Engelmann spruce–subalpine fir type in the central and southern Rocky Mountains. USDA, For. Serv., Washington DC, Agric. Handb. 659. 144 p.
- Noble, D.L.; Ronco, F. 1978. Seedfall and establishment of Engelmann spruce and subalpine fir in clearcut openings in Colorado. USDA, For. Serv., Rocky Mountain For. Range Exp. Sta., Res. Pap. RM-200. 12 p.
- Eis, S. 1967. Establishment and early development of white spruce in the interior of British Columbia. For. Chron. 43:174–177.
- Day, M.W.; Rudolph, V.J. 1970. Development of a white spruce plantation. Michigan State Univ., Agric. Exp. Sta., East Lansing MI, Res. Pap. 111. 4 p.
- "Milestones of Flight - 1903 Wright Flyer" - Smithsonian National Air and Space Museum
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- Stubbs, Brett J. (June 2003). "Captain Cook's beer: the antiscorbutic use of malt and beer in late 18th century sea voyages". Asia Pacific Journal of Clinical Nutrition (apjcn.nhri.org.tw) 12 (2): 129–137. Retrieved 2009-10-08.
- The healing trees / Spruce
- Graves, A.H. 1914. Notes on diseases of trees in the southern Appalachians. Phytopath. 4:63–72.
- Davis, C. 1997. [September 24] Tree talk. The Sault Star, Sault Ste. Marie, Ontario. Wednesday, September 24, 1997. p. B2.
- Jorgensen, E. and Cafley, J.D. 1961. Branch and stem cankers of white and Norway spruces in Ontario. For. Chron. 37(4):394–400.
- Ouellette, G.B.; Bard, G. 1962. Observations on a canker and resinosis in white and Norway spruce. Can. Dep. For., For. Ent. Path. Branch, Ottawa ON, Bi-mo. Progr. Rep.18(2):2.
- Wagg, J.W.B. 1963. Notes on food habits of small mammals of the white spruce forest. For. Chron. 39(4):436–445.
- Schopmeyer, C.S.; Helmers, A.E. 1947. Seeding as a means of reforestation in the northern Rocky Mountain Region. USDA For. Serv., Washington DC, Circular 772. 30 p.
- Smith, J.H.G. 1955 [1956 acc to E3999 bib]. Some factors affecting reproduction of Engelmann spruce and alpine fir. British Columbia Dep. Lands For., For. Serv., Victoria BC, Tech. Publ. 43 p. [Coates et al. 1994, Nienstaedt and Teich 1972]
- Zasada, J.C.; Foote, M.J.; Deneke, F.J.; Parkerson, R.H. 1978. Case history of an excellent white spruce cone and seed crop in interior Alaska: cone and seed production, germination and seedling survival. USDA, For. Serv., Pacific NW For. Range Exp. Sta., Portland OR, Gen. Tech. Rep. PNW-65. 53 p.
- Radvanyi, A. 1970b. Small mammals and regeneration of white spruce forests in western Alberta. Ecology 51(6):1102–1105.
- Radvanyi, A. 1972. Small mammals and regeneration of white spruce in western Alberta. p. 21–23 in McMinn, R.G. (Ed.). White Spruce: Ecology of a Northern Resource. Can. Dep. Environ., Can. For. Serv., Edmonton AB, Inf. Rep. NOR-X-40.
- Rowe, J.S. 1952. Squirrel damage to white spruce. Can. Dep. Resour. Devel., For. Branch, For. Res. Div., Ottawa ON, Silv. Leafl. 61. 2 p.
- Nienstaedt, H. 1957. Silvical characteristics of white spruce (Picea glauca). USDA, For. Serv., Lake States For. Exp. Sta., St. Paul MN, Pap. 55. 24 p.
- McLeod, J.W. 1956. Plantations of the Acadia Forest Experiment Station. Can. Dep. Northern Affairs National Resour., For. Branch, For. Res. Div., Ottawa ON, Tech. Note 31. 25 p.
- Lutz, H.J. 1951. Damage to trees by black bears in Alaska. J. For. 49:522–523.
- Littlefield, E.W.; Schoomaker, W.J.; Cook, D.B. 1946. Field mouse damage to coniferous plantations. J. For. 44:745–749.
- Harper, Douglas. spruce. Online Etymology Dictionary. Accessed 8 May 2010.
|Wikimedia Commons has media related to Picea.|
- Arboretum de Villardebelle: Cones of selected species of Picea: page 1, Arboretum de Villardebelle page 2
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