Traité Gén. Conif., ed. 2 250. 1867.
Trees to 40m; trunk to 1.5m diam.; crown conic. Bark charcoal gray to reddish brown, scaly and deeply fissured. Twigs yellow-brown, glabrous to densely pubescent. Buds oblong, 3–4mm. Leaves 10–25(–30)mm, mostly spreading in all directions from twigs, curved toward twig apex, thickened centrally along midline, somewhat rounded or 4-angled in cross section, both surfaces glaucous, with ±inconspicuous stomatal bands; margins entire. Seed cones oblong-cylindric, 3–6 × 1.5–3cm; scales broadly fan-shaped, 8–15 × 8–15mm, apex rounded to pointed. 2n =24.
Habitat: Coastal and montane forests to alpine slopes (where it occurs in krummholz form)
B.C., Alaska, Calif., Idaho, Mont., Nev., Oreg., Wash.
The wood of Tsuga mertensiana is somewhat inferior to that of western hemlock both for building purposes and as pulp. This is a very handsome tree with its branches densely clothed with pale, spreading leaves and is adaptable to a wide variety of climatic conditions.
M.Van Campo-Duplan and H.Gaussen (1948) postulated that this taxon originated by hybridization between Picea and Tsuga. Although this is unlikely, some characteristics such as leaf arrangement and shape, phenolic chemistry, and pollen grain structure lend some support for this hypothesis.