This species displays some interesting morphological variation. Some authorities discriminate populations east and west of the Cascade crest as Abies grandis var. grandis and Abies grandis var. idahoensis Silba 1990 (syn.: Abies grandis subsp. idahoensis Silba 2008). The distinction between the two varieties, although not generally remarked in the American literature, has been known for a long time in Britain from provenance trials (Lines 1979), which showed that trees from coastal origins grow about twice as fast as those from interior origins, the latter being similar to A. concolor in growth rate. There are also some foliage and cone differences; var. grandis has very flat shade foliage, whereas var. idahoensis has more assurgent shade foliage (similar to that of A. concolor var. lowiana). Also, var. grandis has slightly more slender cones with thinner, less woody scales (M. Frankis e-mail 2009.07.12). Both of these varieties can also be treated as subspecies; I prefer to use varietal rank as the differences are ecotypical, of the sort that can arise within a few generations and may be post-glacial in origin. However the distinction between subspecies and variety is admittedly a subtle one.
Near its southern range limits, A. grandis introgresses A. concolor var. lowiana; populations of such trees (A.concolor × grandis) are sometimes called "Abies grandicolor." Within the zone of introgression individual populations may contain trees displaying characters ranging from very good coastal A. grandis to Sierra Nevada-typical A. concolor var. lowiana. Hunt (1993) is of the opinion that specimens in lower, wetter habitats are best assigned to A. grandis; those in higher, drier habitats, to A. concolor. My field observations, though, suggest that the higher habitats are the wetter (cooler, more snowy) ones, and the trees there resemble A. grandis, shifting toward A. concolor characteristics at lower elevations and on southerly aspects.
Trees to 75 m tall and 155 cm dbh; "crown conic, in age round topped or straggly. Bark gray, thin to thick, with age becoming brown, often with reddish periderm visible in furrows bounded by hard flat ridges. Branches spreading, drooping; twigs mostly opposite, light brown, pubescent. Buds exposed, purple, green, or brown, globose, small to moderately large, resinous, apex round; basal scales short, broad, equilaterally triangular, slightly pubescent or glabrous, resinous, margins entire, apex pointed or slightly rounded. Leaves (1)2-6 cm × l.5-2.5 mm, 2-ranked, flexible, with leaves at center of branch segment longer than those near ends, or with distinct long and short leaves intermixed, proximal portion ± straight, leaves higher in tree spiraled and 1-ranked; cross section flat, grooved adaxially; odor pungent, faintly turpentinelike; abaxial surface with 5-7 stomatal rows on each side of midrib; adaxial surface light to dark lustrous green, lacking stomates or with a few stomates toward leaf apex; apex distinctly notched (rarely rounded); resin canals small, near margins and abaxial epidermal layer. Pollen cones at pollination bluish red, purple, orange, yellow, or ± green. Seed cones cylindric, (5)6-7(12) × 3-3.5 cm, light green, dark blue, deep purple, or gray, sessile, apex rounded; scales ca. 2-2.5 × 2-2.5 cm, densely pubescent; bracts included. Seeds 6-8 × 3-4 mm, body tan; wing about 1.5 times as long as body, tan with rosy tinge; cotyledons (4)5-6(7). 2n=24" (Hunt 1993).
Canada: British Columbia; USA: Montana, Idaho, Washington, Oregon and California at 0-1500 m in moist conifer forests (Hunt 1993). Hardy to Zone 6 (cold hardiness limit between -23.2°C and -17.8°C) (Bannister and Neuner 2001). See also Thompson et al. (1999).
Largest volume: Height 77 m, dbh 185 cm, stem volume 68.3 m3 in 1988; along Duckabush River Trail, Olympic National Park, WA (Van Pelt 1996).
Largest diameter: Height 75.0 m, dbh 220 cm; along the Chilliwack River, BC (Robert Van Pelt , who measured the tree; e-mail 1998.03.18).
Tallest: Height 81.4 m, dbh 158 cm, stem volume 53.0 m3 in 1993; in the Glacier Peak Wilderness, WA (Van Pelt 1996).
Aho (1977) cites a ring count of 472, of which 163 rings are in the first 7.6 cm of the sample (the tree was 87.6 cm DBH and 33.5 m tall). This indicates that the tree attained an impressive age because it spent a long time as a small suppressed advance regeneration tree in the forest understory. A similar situation has been observed among the oldest individuals of Abies amabilis and Abies lasiocarpa, as well as in various species of Picea and Tsuga.
In western Washington and western Oregon, the coastal form of the species is relatively uncommon. Some fine examples can be found along the south shore of Lake Crescent in Olympic National Park; the largest specimen of the species was formerly found here (felled by a severe storm). As noted above (Big trees), some exceptional trees can also be found along the Duckabush River in the eastern Olympics, along the Chilliwack River in British Columbia, and in the Glacier Peak Wilderness.
Var. idahoensis is exceedingly common in riparian settings along streams and rivers within its range. It typically occurs at fairly low elevations, in the company of Pinus ponderosa and Pseudotsuga menziesii var. glauca, and with increasing elevations commonly surrenders to competition with Picea engelmannii. Probably the finest stand I have seen is along White Pine Creek in Washington's Chiwaukum Mountains (47.756°N, 120.941°W), where a portion of the valley is filled by an old growth Abies grandis stand with many trees over a meter in diameter. As the name suggests, it is also a great place to see big Pinus monticola.
Abies grandicolor is quite common in the Klamath Mountains along the road from Happy Camp, California to Cave Junction, Oregon. Look for it at elevations above 1000m while still south of the California-Oregon border. This is also a very good place to see Picea breweriana, as well as a host of other conifers including Abies magnifica × procera, Pinus attenuata, Pinus lambertiana, Pinus jeffreyi, Pseudotsuga menziesii, Calocedrus decurrens, Chamaecyparis lawsoniana, and a shrubby form of Taxus brevifolia.
Aho, P. E. 1977. Decay of grand fir. USDA Forest Service Research Paper PNW-229. Portland, OR: Pacific Northwest Forest and Range Experiment Station. 18 p.
Lines, R. 1979. Natural variation within and between the silver firs. Scottish Forestry 33(2):89-101.
Farjon (1990) provides a detailed account, with illustrations.
Last Modified 2012-11-28