Picea Sitchensis: An In-Depth Guide

World's record Sitka Spruce is more than 55 feet in circumference, 17.68 feet in diameter and 191 feet tall at Quinault Lake, Washington, on August 22, 2018. USDA

Picea sitchensis, commonly known as the Sitka spruce, is a vital coniferous tree in the Pinaceae family. Native to the west coast of North America, this species is renowned for its robust nature and impressive height, making it an essential component of its native ecosystems and a striking addition to varied landscapes.

Key Characteristics

Height and Structure: In landscape and urban settings, Sitka spruce generally reaches heights of 80-120 feet (25-36 meters), and in some cases up to 160 feet (49 meters), with a broadly conical form and thin, horizontally spreading branches.
Bark and Leaves: Features gray, smooth, and thin bark, becoming purplish-brown with age. Needles are stiff, 0.5 to 1 inch (15-25 mm) long, glossy green above, and silvery-white below.
Cones: Cylindrical-oblong, approximately 2.5 to 4 inches (6-10 cm) , with thin, flexible scales.

Habitat and Growth

Thriving in moist, cool climates, Sitka spruce is often found along riverbanks and coastal areas with high humidity. It prefers well-drained, acidic soils and is known for its fast growth rate and longevity. Hardy in USDA Zone 7, this species requires high soil moisture and high humidity and is found primarily in moisture-rich maritime environments.

Landscape Use

Ideal Settings and Design Considerations

Suitable for large open spaces like parks and estates.
Effective as windbreaks or natural screens in large properties.
Minimal pruning is needed, but monitoring for health is essential.

Aesthetic and Companion Plantings

Provides year-round color and texture as an evergreen.
It pairs well with shade-tolerant understory plants and other native species like Western Hemlock or Douglas Fir.

Conservation and Threats

Sitka Spruce faces challenges from logging, habitat loss, and climate change, with conservation efforts focusing on protecting old-growth forests and sustainable timber practices. In the Willamette Valley, adelgids, aphid-like insects, produce galls on the tips of young twigs of Sitka spruce, causing their death.

Pest and Disease Concerns

White Pine Weevil and Spruce Beetles: These are potential insect problems for Sitka spruce, which landscape managers and arborists should monitor and manage.

Wildlife Support

Bird Habitat

Sitka spruce forests are crucial habitats for various wildlife, especially birds.
They provide excellent nesting and roosting habitats for avifauna, including primary and secondary cavity nesters.
Notably, bald eagles predominantly use Sitka spruce for nesting, while peregrine falcons in coastal British Columbia utilize these trees for platform and cavity nesting.

Mammal Cover

The forests offer essential cover for mammals like Sitka deer, Roosevelt elk, woodland caribou, Alaskan brown bear, and mountain goat.
Old-growth Sitka spruce forests are particularly important as winter habitats, providing thermal cover and facilitating access to food sources.

Cultivar: Papoose Sitka Spruce (Picea sitchensis 'Papoose')

The Papoose Sitka Spruce (Picea sitchensis 'Papoose') is a coniferous evergreen cultivar native to Oregon and part of the Pinaceae family. Initially forming a dense, globe-shaped shrub, it gradually evolves into a broadly conical form, growing about 1.57 inches (4cm) per year. Its distinctive bicolored foliage, blending blue and green, features short, sharp needles. Suited for full sun, 'Papoose' thrives in moist to wet, sandy soil and cool air, showing hardiness in USDA Zone 7. It was discovered on Vancouver Island, British Columbia, and was later shared with William Goddard of Floravista Gardens around 1964. (Oregon State University)

Conclusion

The Sitka spruce, with its notable stature and ecological significance, is a remarkable species and an impressive landscape feature. While it offers year-round beauty and ecological benefits, its specific environmental needs limit its suitability for certain landscapes. Understanding and preserving this species is crucial for maintaining the biodiversity and balance of Pacific Northwest forests and beyond.

Additional Reading

The Morton Arboretum. (n.d.). Sitka spruce. Retrieved from https://www.mortonarb.org/trees-plants/tree-plant-descriptions/sitka-spruce.
U.S. Forest Service Research and Development. (n.d.). Sitka Spruce. Retrieved from https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/picea/sitchensis.htm.
North Carolina State University. (n.d.). Picea sitchensis (Coast Spruce, Sitka Spruce, Tideland Spruce). Retrieved from https://plants.ces.ncsu.edu/plants/picea-sitchensis/.
Oregon State University. (n.d.). Picea sitchensis. Retrieved from https://landscapeplants.oregonstate.edu/plants/picea-sitchensis.
University of Washington. (n.d.). Sitka spruce. Retrieved from https://depts.washington.edu/propplnt/Plants/Sitka_spruce.htm