Subalpine fir (Abies lasiocarpa): what the agencies record

This page reports what US federal publications say about one tree. It does not identify trees from descriptions or photos and does not say what should be done with any tree. The family overview, tree species in the agency records, explains the sources and holds the comparison table.

At a glance

Item	What the source records
Scientific name	Abies lasiocarpa (Hook.) Nutt. in USDA PLANTS, pine family; Silvics also recognizes corkbark fir (Abies lasiocarpa var. arizonica)
Other names	Balsam, white balsam, alpine fir, western balsam fir, Rocky Mountain fir and others for the typical variety; corkbark fir for the Southwest variety (Silvics)
Native status, USDA PLANTS	Native in Alaska, Canada and the lower 48 states
Size, Silvics	Under closed-forest conditions 30 to 61 cm (12 to 24 in) in diameter and 14 to 30 m (45 to 100 ft) tall, depending on site and stand density; trees larger than 76 cm (30 in) and 39.6 m (130 ft) are exceptional; on exposed sites near timberline it is often reduced to a prostrate shrub
Age, Silvics	Growth is not rapid: trees 25 to 51 cm (10 to 20 in) across are often 150 to 200 years old in closed forest, and trees older than 250 years are not uncommon
Green weight of the wood, NRS-38	28 lb per cubic foot, without bark

Native range

The Silvics of North America handbook (Agriculture Handbook 654, volume 1, 1990) calls subalpine fir the smallest of eight true fir species indigenous to the western United States and a widely distributed North American fir, with a range from 32 degrees north latitude in Arizona and New Mexico to 64 degrees 30 minutes north in Yukon Territory. Along the Pacific coast the range extends from southeastern Alaska through British Columbia along the east slopes of the Coast Range to the Olympic Mountains of Washington and along both slopes of the Cascades to southern Oregon. It is absent from the west slopes of the Coast Range in southern British Columbia and from the Coast Range of Washington and Oregon, though Vancouver Island has it, and it is found locally in northeastern Nevada and northwestern California.

In the Rocky Mountain region it extends from the interior valleys of British Columbia south along the high elevations of the Rocky Mountain system to southern New Mexico and Arizona. Corkbark fir, the only recognized natural geographical variety, is described as readily distinguished by its whitish, corky bark and restricted to the Rocky Mountains of southern Colorado and the Southwest.

Flowers, cones and roots

Silvics says subalpine fir is monoecious, with male flowers in pendulous clusters on the lower branchlets and fewer female flowers borne erect on the uppermost branchlets of the crown. Pollen is wind-disseminated during late spring and early summer, cones are indigo blue when they open in mid-August to mid-October, and seed ripens from mid-September to late October. The handbook says the species has a shallow root system on sites that limit root penetration, with the superficial lateral root system of the seedling stage persisting to old age, and a relatively deep lateral root system under more favorable conditions.

Growth and stands

The handbook says subalpine fir usually grows in mixed stands and makes up only a minor part of the volume. Where it grows with Engelmann spruce in the Rocky Mountains and Pacific Northwest it usually makes up only 10 to 20 percent of the saw log volume. It says pure stands in the Rocky Mountains occur most often on sites so severe that the species has little commercial value, while in the Pacific Northwest pure stands on commercial sites typically occur on southerly slopes and are usually less than 150 years old. On special uses, Silvics says the forests where subalpine fir grows occupy the highest water yield areas in much of the West, and that the species has no special or unique properties in much of the Rocky Mountains.

Wood

The Wood Handbook (FPL-GTR-282, 2021) groups subalpine fir with the western true firs, whose wood-use description is set out once on the white fir page. Silvics says fir is used as lumber in building construction, boxes, crates, planing mill products, sashes, doors, frames and food containers, and that it has not been widely used for pulpwood because of inaccessibility, though it can be pulped by the sulfate, sulfite or groundwood processes. Table 5-3b has a separate subalpine fir row, shown below.

Wood Handbook Table 5-3b	Specific gravity	Modulus of rupture (lbf per square inch)	Side hardness (lbf)
Green	0.31	4,900	260
At 12% moisture content	0.32	8,600	350

The Wood Handbook states that specific gravity is based on oven-dry weight and the volume when green or at 12% moisture content. The green weight of the wood without bark is in the NRS-38 table, the same figure used in the log weight calculator.

Diseases, insects and damage the handbook names

Silvics (1990) names these agents by the names it used.

Windthrow. The handbook says subalpine fir is susceptible to windthrow, generally attributed to a shallow root system, though soil depth, drainage, stand conditions, the kind and intensity of cutting and topographic exposure also influence it.
Budworm and bark beetles. In spruce-fir forests the most important insect pests are the western spruce budworm (Choristoneura occidentalis) and the western balsam bark beetle (Dryocoetes confusus). The silver fir beetle and the fir engraver may at times be destructive locally.
Balsam woolly adelgid. In the Cascades the handbook calls this European introduction (Adelges piceae) the most destructive insect pest, saying it has caused significant mortality to subalpine fir and virtually eliminated it from some stands in Oregon and southern Washington.
Broom rust and wood rots. Fir broom rust (Melampsorella caryophyllacearum) and wood rotting fungi are said to be responsible for most disease losses. Important root and butt rots listed are Gloeocystidiellum citrinum, Coniophora puteana, Armillaria mellea, Coniophorella olivaea, Polyporus tomentosus var. circinatus and Pholiota squarrosa, and important trunk rots are Haematostereum sanguinolentum, Phellinus pini and Amylostereum chailletii. The handbook says wood rots and broom rust weaken affected trees and predispose them to windthrow and windbreak.
Heart rot and fire. Silvics says the species suffers severely from heart rot, and that its bark is thin, especially on young trees, with lower limbs persisting after death, which makes it susceptible to death or severe injury from fire.

The guide on decay fungi covers the rot group in general.

The guide on reporting a pest in the United States and the Canada reporting page give the offices that take sightings of regulated pests. Who may apply pesticides is in pesticide licences by country.