Two subspecies, engelmannii (described here) and mexicana.
"In the northern part of its range, it hybridizes freely and completely intergrades with P. glauca" (Taylor 1993). This hybrid is commonly called "interior spruce" or P. glauca var. albertiana. In the Chilliwack River Valley of British Columbia, P. engelmannii occurs with and hybridizes with Picea sitchensis. The area is near sea level and the Fraser Valley, yet comes right out of the heart of the North Cascades. This hybrid may occur elsewhere, where the species' ranges are contiguous (such as the Federation Forest/Crystal Mountain area of Washington) but has not been seen yet (Van Pelt 1999). All three species (P. engelmannii, glauca, and sitchensis) hybridize is a zone in the interior Skeena River valley in British Columbia (Sutton et al. 1994).
Additional synonymy for var. engelmannii (Taylor 1993):
"Trees to 45 m, rarely to 60 m; trunk to 1.2 m, rarely 2 m diam.; crown narrowly conic. Bark gray to reddish brown. Branches spreading horizontally to somewhat drooping; twigs not pendent, rather stout, yellow-brown, finely pubescent, occasionally glabrous. Buds orange-brown, 3-6mm, apex rounded. Leaves 1.6-3(3.5) cm, 4-angled in cross section, rigid, blue-green, bearing stomates on all surfaces, apex sharp-pointed." Seed cones violet or deep purple, ripening buff-brown, "3-7(8) cm; scales diamond-shaped to elliptic, widest above middle, 13-20 × 9-16 mm, flexuous, margin at apex irregularly toothed to erose, apex extending 3-8mm beyond seed-wing impression. 2n=24" (Taylor 1993).
Canada: Alberta, British Columbia; USA: Washington, Idaho, Montana, Wyoming, Colorado, Oregon, California, Nevada, Utah, Arizona, New Mexico; as krummholz at the alpine timberline (Taylor 1993). See also Thompson et al. (1999). UHardy to Zone 3 (cold hardiness limit between -39.9°C and -34.4°C) (Bannister and Neuner 2001).
The subsp. mexicana occurs in N Mexico and southern Arizona and New Mexico (Taylor and Patterson 1980: p.438) at 1000-3000 m in montane and subalpine forests.
The largest tree, the North Joffre Spruce in British Columbia, is 220 cm dbh and 41 m tall. A tree named the Easy Pass Tower growing along the North Cascades Highway (Washington Route 20) near the Easy Pass Trailhead is 67.7 m tall and 169 cm dbh (Robert Van Pelt e-mail 2004.02.04). Quite a few comparably tall trees grow in the vicinity. A larger tree from the Payette Lake (Idaho) at 63 m3 had the largest volume ever recorded for this species, but fell victim to bark beetles (Van Pelt 1999).
Tree FCC 23 in central Colorado had a crossdated age of 911 years (Brown et al. 1995, cited in RMTRR 2006). Also, a crossdated age of 852 years for specimen FCC 19, collected in 1994(?) from a stand near the alpine timberline at the headwaters of Fool Creek in Fraser Experimental Forest, Colorado. Also, a crossdated age of 760 years for a specimen from near Peyto Glacier in Alberta collected by B.H. Luckman (Brown et al. 1995). I believe this was from a living tree collected in the late 1980s or early 1990s.
Have one Medicine Bow chronology (Earle 1993), and numerous population studies exist.
Engelmann spruce and subalpine fir form one of the most common forest associations in the Rocky Mountains. They can be seen, for example, in all Rocky Mountain National Parks from Jasper in Canada to Rocky Mountain in Colorado. They also form a dominant forest type in eastern North Cascades National Park and the Pasayten Wilderness in Washington. The southernmost Engelmann spruce stand in the U.S. can be found atop the Chiricahua Mountains of Arizona; this population is now referred to subsp. mexicana (Taylor and Patterson 1980: p.438).
B. C. S. Sutton, S. C. Pritchard, J. R. Gawley, C. H. Newton, and G. K. Kiss. 1994. Analysis of Sitka spruce–interior spruce introgression in British Columbia using cytoplasmic and nuclear DNA probes. Canadian Journal of Forest Research 24(2):278-285.
This page co-edited with Michael P. Frankis, 1998.12.
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. Canadian Journal of Botany 46:649-687.
Last Modified 2013-12-10