Abies lasiocarpa (Subalpine Fir)

Abies lasiocarpa, also known as the Subalpine Fir or Rocky Mountain Fir, is a North American fir species belonging to the pine family (Pinaceae).

Native: Subalpine Fir is native to the high elevation, cool, and moist climates of western North America, stretching from Alaska through the western United States to northern Mexico. It thrives in mountainous areas, hence its common name, and is often found at the tree line.

Description: Subalpine Fir is a slender, spire-like coniferous tree. It boasts a narrow, spire-like crown with short, dense branches covered in smooth bark that’s gray to whitish-gray. The tree’s needles are blue-green, curved upward to expose two blue-white bands below, creating a silvery appearance.

Size: It typically reaches heights of 20-90 feet (6-27 meters) with a spread of 10-20 feet (3-6 meters). In the mountains, it can grow to a height of up to 90 feet (27 meters), with only 10 feet (3 meters) of width. In gardens, Subalpine Fir is usually shorter and loses its narrow shape. Slow-growing, it may never exceed 20 feet in height but spread to 15-20 feet (4.5-6 meters) in width.

Cones: The tree produces cylindrical, upright cones 2-4 inches (5-10 cm) long. These cones are initially green or purple, turning brown as they mature. They disintegrate on the tree to release their winged seeds, which are dispersed by the wind.

Hardiness: Abies lasiocarpa is hardy and adapted to USDA Hardiness Zones 5-6.

Soil and Sunlight: This fir thrives in well-drained, acidic soils and prefers cooler climates with high rainfall. It’s a shade-tolerant species and can persist under the forest canopy until a gap opens up, at which point it grows quickly towards the light. Due to its tolerance for cold, harsh conditions, it’s often found growing in rocky and poor soils where other species cannot thrive.

Uses: Subalpine Fir is used for Christmas trees and as an ornamental tree in large parks and gardens due to its unique growth habit and attractive foliage. Its wood, though not commercially valuable due to the tree’s typically small size and slow growth rate, is sometimes used for pulp. It can be used as a bonsai.

Benefits: Subalpine Fir trees play a crucial role in watershed protection in their native mountain habitats. Their root systems help stabilize steep slopes, reducing soil erosion. These trees also help mitigate climate change by acting as carbon sinks.

Wildlife: Subalpine Fir provides habitat and food for a variety of wildlife. Its seeds are favored by squirrels, birds, and other small mammals. The tree’s dense foliage provides shelter for various bird species.

Deer and Rabbits: Deer and rabbits do browse on Subalpine Fir, particularly during the winter months when other food sources are scarce. However, the tree’s high-elevation habitat limits its exposure to these animals.

Toxicity: There’s no known toxicity of the Subalpine Fir to humans or pets. However, the sap can cause skin irritation in some individuals.

Pruning: No pruning is required

Propagation: The most common propagation method for Subalpine Fir is from seeds. Collect cones in the fall once they’ve dried out and before they open. Place the cones in a paper bag and allow them to dry until they open and release their seeds. Seeds can then be sown in well-draining soil and placed in a cold frame or greenhouse for protection. Seeds often benefit from a period of cold stratification before planting, which involves storing them in moist sand or peat moss in a sealed plastic bag in the refrigerator for a few weeks to a few months. This helps to break seed dormancy and stimulate germination. Once seedlings are large enough to handle, they can be transplanted to their permanent location.

Pests and Diseases: Pests and diseases can vary significantly by geographic region and local environmental conditions. The list below does not include every potential disease or pest issue. When treating disease or pest problems, it’s best to consult with a local extension service or professional arborist for specific recommendations.

Pests:

• Balsam Woolly Adelgids (Adelges piceae): These are small, aphid-like insects that feed on the sap of fir trees, causing deformation of new growth, resulting in a “woolly” appearance, and, eventually, tree death.
• Bagworms (Thyridopteryx ephemeraeformis): Caterpillars that construct spindle-shaped bags covered with pieces of twigs and leaves. They defoliate trees, which can lead to reduced growth, branch dieback, and tree death in severe infestations.
• Fir Engraver Beetle (Scolytus ventralis): These beetles bore into the bark of the tree, which can cause the browning of the foliage and the eventual death of the tree.
• Spruce Budworms (Choristoneura spp.): This is the larval stage of a moth that primarily feeds on the buds and needles of spruce and fir trees. Infestations can cause severe defoliation and reduce tree vigor.
• Spruce Spider Mite (Oligonychus ununguis): These mites cause damage by sucking sap from the undersides of needles, leading to a speckled or mottled appearance.
• Western Balsam Bark Beetle (Dryocoetes confusus): Small, reddish-brown beetles that attack stressed fir trees. Damage: Their tunnels cut off nutrient and water flow, potentially leading to branch dieback or tree death.

Diseases:

• Cankers: These are areas of dead tissue on the bark of a tree, often caused by fungal pathogens. Cankers can girdle branches or trunks, disrupting nutrient flow and causing dieback.
• Heart Rot: A fungal disease that causes decay in the heartwood of the tree.
• Needle Cast: This is a fungal disease that causes needles to turn color (usually brown or yellow) and drop prematurely from the tree. Over time, it can significantly weaken the tree and make it more susceptible to other stressors.
• Needle Rust: This is a fungal disease that causes yellow to orange pustules on needles. Infected needles often drop prematurely, and severe infections can lead to significant defoliation.
• Root Rot: This is a condition typically caused by a variety of soil-borne fungi. It causes the decay and death of root tissue, leading to a decline in the tree’s health and potentially causing tree death.
• Twig Blight: This is a condition usually caused by fungal pathogens, leading to the death of twigs and small branches. Symptoms often include discoloration, wilting, and dieback of twigs and branches.

Fun Facts:

• Subalpine Fir trees can live up to 250 years.
• The tree’s common name comes from its typically high-altitude habitat.
• Native Americans employed the leaves as a deodorant and burned them as incense or medicinal vapor.