Morphology thumb|The peg-like base of the needles, or pulvinus, in Norway spruce (Picea abies) thumb|Pulvini remain after the needles fall (white spruce, Picea glauca) Determining that a tree is a spruce is not difficult; evergreen needles that are more or less quadrangled, and especially the pulvinus, give it away. Beyond that, determination can become more difficult. Intensive sampling in the Smithers/Hazelton/Houston area of British Columbia showed Douglas (1975),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 For., Forest Science, Smithers BC, unpublished report, cited by Coates et al. 1994.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) according to Coates et al. (1994),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. 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 two latter characters. Taylor (1959) (Cited in Coates et al. 1994). had noted that the most obvious morphological difference between typical Picea glauca and typical P. engelmannii was the cone scale, and Horton (1956,1959)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. found that the most useful diagnostic features of the two 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)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. recommended that cone scale characters be based on samples taken from the midsection of each of ten cones from each of five trees in the population of interest.
Morphology thumb|The peg-like base of the needles, or pulvinus, in Norway spruce (Picea abies) thumb|Pulvini remain after the needles fall (white spruce, Picea glauca) Determining that a tree is a spruce is not difficult; evergreen needles that are more or less quadrangled, and especially the pulvinus, give it away. Beyond that, determination can become more difficult. Intensive sampling in the Smithers/Hazelton/Houston area of British Columbia showed Douglas (1975),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) according to Coates et al. (1994),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. 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 two latter characters. Taylor (1959) (Cited in Coates et al. 1994). had noted that the most obvious morphological difference between typical Picea glauca and typical P. engelmannii was the cone scale, and Horton (1956,1959)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. found that the most useful diagnostic features of the two 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)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. recommended that cone scale characters be based on samples taken from the midsection of each of ten cones from each of five trees in the population of interest.