Flora of North America species comparison

Varieties 2 (1 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)