4. Picea glauca (Moench) Voss, Mitt. Deutsch. Dendrol. Ges. 16: 93. 1907.
White spruce, western white spruce, Porsild spruce, Black Hills spruce, épinette blanche
Pinus glauca Moench, Verz. Ausländ. Bäume, 73. 1785; Abies canadensis Miller; Picea alba (Aiton) Link; P. alba var. albertiana (S.Brown) Beissner; P. albertiana S.Brown; P. canadensis (Miller) Britton, Sterns, & Poggenburg; P. canadensis var. glauca (Moench) Sudworth; P. glauca var. albertiana (S.Brown) Sargent; P. glauca var. densata Bailey; P. glauca var. porsildii Raup; Pinus alba Aiton
Trees to 30m; trunk to 1m diam.; crown broadly conic to spirelike. Bark gray-brown. Branches slightly drooping; twigs not pendent, rather slender, pinkish brown, glabrous. Buds orange-brown, 3--6mm, apex rounded. Leaves (0.8--)1.5--2(--2.5)cm, 4-angled in cross section, rigid, blue-green, bearing stomates on all surfaces, apex sharp-pointed. Seed cones 2.5--6(--8)cm; scales fan-shaped, broadest near rounded apex, 10--16 ´ 9--13mm, flexuous, margin at apex ± entire, apex extending 0.5--3mm beyond seed-wing impression. 2 n =24.
Muskegs, bogs, and river banks to montane slopes; 0--1000m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Maine, Mich., Minn., Mont., N.H., N.Y., S.Dak., Vt., Wis., Wyo.
In areas of sympatry Picea glauca and P . engelmannii regularly hybridize and intergrade completely (R.Daubenmire 1974; E.H. Garman 1957; K.W. Horton 1959; L.Roche 1969; T.M.C. Taylor 1959). This has greatly complicated the taxonomy of P . glauca , a dominant tree of interior forests of Canada and Alaska. Three varieties have been recognized. Picea glauca var. albertiana was described as having unusually prominent leaf bases, cones nearly as broad as long, cone scales acute and broader than long, and an unusually narrow crown. These are common characteristics of hybrids (e.g., R.Daubenmire 1974). Picea glauca var. porsildii was described as differing from the type variety by having smooth bark with resin blisters, short angular cone scales, an unusually broad crown, and pubescent twigs. These characteristics, also largely intermediate between those of P . glauca var. glauca and P . engelmannii , may reflect hybridization where the species overlap. Although the two varieties noted above are reported from well beyond the range of sympatry, the diagnostic characteristics are not well correlated and occur rather sporadically. Also the most distinctive feature of the varieties, the crown shape, is in part responsive to competitive pressures. Because of the problems of hybridization and sporadic occurrence of key characters, P . glauca is treated here in the broad sense.
Picea glauca (white spruce) is the provincial tree of Manitoba and the state tree (as Black Hills spruce) of South Dakota.
LaRoi, G.H. and J.R. Dugle. 1968. A systematic and genecological study of Picea glauca and P. engelmannii, using paper chromatography of needle extracts. Canad. J. Bot. 46: 649--687. Little, E.L. Jr. and S.S. Pauley. 1958. A natural hybrid between black and white spruce in Minnesota. Amer. Midl. Naturalist 60: 202--211.