Grand Fir (Abies grandis)

Grand Fir (Abies grandis) is a towering evergreen tree native to the American Pacific Northwest. The softwood lumber is useful for papermaking and the citrusy foliage scent makes Abies grandis a popular choice as a Christmas tree. The tallest recorded specimen in the wild is 81 m tall!

I. Appearance and Characteristics

Abies grandis (grand fir, giant fir, lowland white fir, great silver fir, western white fir, Vancouver fir, or Oregon fir) is a fir native to northwestern North America, occurring at altitudes of sea level to 1,700 meters (5,600 ft). It is a major constituent of the Grand Fir/Douglas Fir Ecoregion of the Cascade Range.

The species was first described by Scottish botanical explorer David Douglas, who in 1830 brought its seeds back to Britain; in 1831 he described specimens he had collected along the Columbia River in the Pacific Northwest.

Abies grandis is a large evergreen conifer growing to 40–70 meters (130–230 feet) tall, exceptionally 100 m (330 ft), with a trunk diameter of up to 2 m (6+1⁄2 ft). The dead tree tops sometimes fork into new growth. The bark is 5 centimeters (2 inches) thick, reddish to gray (but purple within), furrowed, and divided into slender plates. The leaves are needle-like, flattened, 3–6 cm (1+1⁄8–2+3⁄8 in) long and 2 millimeters (3⁄32 in) wide by 0.5 mm thick, glossy dark green above, with two green-white bands of stomata below, and slightly notched at the tip.

The leaf arrangement is spiral on the shoot, but with each leaf variably twisted at the base so they all lie in two more-or-less flat ranks on either side of the shoot. On the lower leaf surface, two green-white bands of stomata are prominent. The base of each leaf is twisted a variable amount so that the leaves are nearly coplanar.

The green-to-reddish cones are 6–12 cm (2+1⁄4–4+3⁄4 in) long and 3.5–4.5 cm (1+1⁄2–1+3⁄4 in) broad, with about 100–150 scales; the scale bracts are short, and hidden in the closed cone. The winged seeds are released when the cones disintegrate at maturity about 6 months after pollination.

Varieties

There are two varieties, probably better treated at subspecies rank though not yet formally published as such:

• Abies grandis var. grandis. Coast grand fir. Coastal lowland forests, at sea level to 900 m altitude, from Vancouver Island and coastal British Columbia, south to Sonoma County, California. A large, very fast-growing tree to 70 m tall. Foliage strongly flattened on all shoots. Cones slightly narrower (mostly less than 4 cm broad), with thinner, fairly flexible scales. Tolerates winter temperatures down to about -25° to -30 °C; growth on good sites may exceed 1.5 m per year when young.
• Abies grandis var. idahoensis. Interior grand fir. Interior forests, at (600–) 900–1800 m altitude, on the east slope of the Cascades in Washington and in the Rocky Mountains from southeast British Columbia south to central Idaho, northeast Oregon and western Montana. A smaller, slow-growing tree to 40–45 m tall. Foliage not strongly flattened on all shoots, the leaves often raised above the shoot, particularly on upper crown shoots. Cones slightly stouter (mostly over 4 cm broad), with thicker, slightly woody scales. Tolerates winter temperatures down to about -40 °C; growth on good sites not exceeding 0.6 m per year even when young.

Grand fir is very closely related to white fir (Abies concolor), and intergrades with it in central Oregon. Firs of the Blue Mountains and Oregon East Cascade Slope are intermediate between the two species in genetics and appearance. The intergrades are often referred to as “Abies grandis x concolor”, a variety which itself intergrades into Abies concolor lowiana farther south, around the California state line.

II. How to Grow and Care

Sunlight

The most difficult task you may face is deciding the amount of sun a grand fir needs. All information will show that the species prefers full sun to part shade, but this is not the full story. Initially, when a grand fir is beginning to establish itself in the wild, it relies on other taller trees to provide shade. As it grows, it will provide the same cover for younger generations, ensuring the species’ survival and receiving the full sun it now needs as a large mature tree.

This is the dilemma — finding a place that will provide part shade to a young tree in the first decades of its life, and full sun to an adult tree in the same landscape while also giving the tree enough space to grow. Overcoming this issue can be dealt with by planting in the shadow of other trees and structures but far enough away that it will get some sun and not encroach on the other plants and structures as it becomes a huge tree in time.

Taking pictures of your landscape at various times of the day is a great way to see how certain plantings and buildings will affect shade and lighting and solve any problems before they even develop.

Temperature and Humidity

Because of the inhospitable climate, grand firs do not do very well in the east of the Pacific Northwest. The species does best in the cool, moist climate of Oregon and Washington state, and pushing eastward will test its hardiness. The USDA recommends zones 5 to 6, but in reality, this is deceiving as the humidity in some areas in these zones will affect the tree.

Watering

The soil of the grand fir needs to be moist at all times. You are not looking for soaking wet soil but moist to the touch down to two-three inches. This is especially important during the first two years after planting and during the summer months. It would be best if you watered as needed at these times, checking the soil for moisture rather than setting a routine. Sometimes it may be necessary to water more often. Let the soil be the judge.

Soil

As mentioned, the conditions that the grand fir are what will determine whether your tree is happy and healthy. Soil conditions for the grand fir are somewhat fussy, it will grow best in very rich, consistently moist soil, that is a bit on the acidic side. Consider the ecosystem the species is native to, the Pacific Northwest, and imagine the soil you’d find on the damp floor of its temperate rainforests. That is what you are working to achieve.

Fertilizing

You should not need to provide the grand fir with any supplemental fertilizer. On its own in the right conditions it has the potential to grow four feet per year. Adding a fertilizer may increase growth you can see but a tree of this size needs time to also establish a good healthy root structure so inducing accelerated growth will not allow this to occur at a relative pace to the rest of the tree.

Pruning

If your grand fir is healthy, you should not need to do any pruning to the wild type, though certain cultivars may call for pruning to establish form. In those cases, refer to any information regarding the cultivar and that particular form.

The grand fir should only need pruning when there are dead or damaged branches. When this happens, be careful to prune branches right up to the trunk at the collar of the damaged branch. Pruning like this will maintain the even conical appearance that grand firs have.

Propagation

Two methods are used to propagate a grand fir. The first and most unreliable, and most time-consuming is by seed. This method is not recommended. The second is done through grafting, usually onto the rootstock of Abies firma. While not very difficult, grafting can take a bit of trial and error and may require some research to understand the full technique before giving it a shot.

Pests and Diseases

There are benefits to being big. When the grand fir reaches maturity, it often becomes large enough to shrug off most issues that plague it. The time to worry is when the tree is young or stressed. During those times, it may be affected by some diseases or pests.

The tree might be bothered by spider mites in hot, dry weather. On the other hand, root rot may become an issue when the soil becomes overly wet and the drainage is poor, leading to soaking wet rather than moist soil. When your grand fir is younger, and you can still give it an overall inspection, keep an eye on it and call a certified arborist at the first sign of any problems.

III. Uses and Benefits

• Ornamental uses

The foliage has an attractive citrus-like scent. It is sometimes used for Christmas decorations in the United States, including Christmas trees, although its stiff branches do not allow it to be economically packed. It is also planted as an ornamental tree in large parks.

• Medicinal uses

Native Americans used both grand fir and white fir, powdering the bark or pitch to treat tuberculosis or skin ailments; the Nlaka’pamux used the bark to cover lodges and make canoes, and branches were used as bedding. The inner bark of the grand fir was used by some Plateau Indian tribes for treating colds and fever. The Okanagan-Colville tribe used the species as a strengthening drug to nullify the feeling of weakness.

• Other uses

Timber

The lumber is non-resinous and fine textured. In the North American logging industry, the grand fir is often referred to as “hem fir”, with hem fir being a number of species with interchangeable types of wood (specifically the California red fir, noble fir, Pacific silver fir, white fir, and western hemlock). Grand fir is often shipped along with these other species. It can also be referred to as “white fir” lumber, an umbrella term also referring to Abies amabilis, Abies concolor, and Abies magnifica.

Lumber from the grand fir is considered softwood. As such, it is used for paper making, packing crates, and construction. Hem fir is frequently used for framing, and is able to meet the building code span requirements of numerous construction projects.

As a hem fir, the trunk of the grand fir is considered slightly below the “Douglas fir-larch” species combination in strength, and stronger than the “Douglas fir-South” and “spruce-pine-fir (South)” species combos (both umbrella terms for a number of species with similar wood). Because it is nearly as strong as Douglas fir-larch, it often meets the structural load-bearing requirements for framing in residential, light commercial, and heavy construction.

Excluding Douglas fir-larch, hem fir’s modulus of elasticity value as a stiffness factor in floor systems (denoted as MOE or E) is stronger than all other western species combinations. Hem fir is preferred by many builders because of its ability to hold and not be split by nails and screws, and its low propensity for splintering when sawed.