Abies lasiocarpa is native to the mountains of Yukon, British Columbia and western Alberta in Western Canada; and to southeastern Alaska, Washington, Oregon, Idaho, western Montana, Wyoming, Utah, Colorado, New Mexico, Arizona, northeastern Nevada, and the Trinity Alps of the Klamath Mountains in northwestern California in the Western United States.
It occurs at high altitudes, from 300–900 metres (980–2,950 ft) in the north of the range (rarely down to sea level in the far north), to 2,400–3,650 metres (7,870–11,980 ft) in the south of the range; it is commonly found at and immediately below the tree line.
It is a medium-sized tree growing to 20 metres (66 ft) tall, exceptionally to 40–50 metres (130–160 ft) tall, with a trunk up to 1 metre (3.3 ft) across, and a very narrow conic crown. The bark on young trees is smooth, gray, and with resin blisters, becoming rough and fissured or scaly on old trees. The leaves are flat and needle-like, 1.5–3 cm (5⁄8–1 1⁄8 in) long, glaucous green above with a broad stripe of stomata, and two blue-white stomatal bands below; the fresh leaf scars are reddish. They are arranged spirally on the shoot, but with the leaf bases twisted to be arranged to the sides of and above the shoot, with few or none below the shoot. The cones are erect, 6–12 cm (2 1⁄4–4 3⁄4 in) long, dark blackish-purple with fine yellow-brown pubescence, ripening brown and disintegrating to release the winged seeds in early fall.
There are two to three taxa in subalpine fir, treated very differently by different authors:
The only unique populations in this species come from coastal Alaska (A. S. Harris 1965; C. J. Heusser 1954). They are found at lower elevations (0--900 m) and appear to be isolated with no reported introgression between them and the coastal mountain populations. The population on the Prince of Wales Island has distinct terpene patterns and needs morphological and developmental studies to see if these patterns contrast with neighboring populations.
Through central British Columbia and northern Washington, Abies lasiocarpa introgresses with A . bifolia . These trees may have morphologic features resembling either species and may have intermediate terpene patterns; they are best classified as interior subalpine fir ( A . bifolia ´ lasiocarpa ). At the southern end of its range, A . lasiocarpa possibly hybridizes with A . procera (R.S. Hunt and E.von Rudloff 1979). Abies lasiocarpa shares with A . procera a red periderm, crystals in the ray parenchyma (R.W. Kennedy et al. 1968), and reflexed tips of the bracts, features not shared with A . bifolia .
Abies lasiocarpa usually exists in small stands at high elevations and is not often observed. Its differences in comparison to A . bifolia have prompted studies (W.H. Parker et al. 1979) to see if it is A . bifolia introgressed with the sympatric A . amabilis . Abies lasiocarpa and A . amabilis , however, are separated by many morphologic features, and no hybrids have been found (W.H. Parker et al. 1979).