Syn: Pinus sitchensis Bongard 1832; Abies falcata Rafinesque; A. menziesii (Douglas ex D. Don) Lindley 1835, not Mirbel 1825; Picea falcata (Rafinesque) Suringar; P. menziesii (Douglas ex D. Don) Carrière; Pinus menziesii Douglas ex D. Don (Taylor 1993).
Freely hybridizes with P. glauca to form Lutz or Roche spruce, P. × lutzii, wherever the ranges of the two species overlap, such as along major river corridors across the British Columbia Coast Range and in coastal Alaska. Analysis of this introgression zone indicates that the region was first colonized by P. sitchensis during late Pleistocene deglaciation, with subsequent introgression when P. glauca arrived via dispersal from Alaskan or eastern Canadian refugia (Hamilton and Aitken 2013). In the Chilliwack River Valley of British Columbia, it occurs with and hybridizes with Picea engelmannii. The area is near sea level and the Fraser Valley, yet comes right out of the heart of the North Cascades. This hybrid may occur elsewhere, where the species' ranges are contiguous (such as the Federation Forest/Crystal Mountain area of Washington) but has not been seen yet (Van Pelt 1999). Hybridization between P. sitchensis and "interior spruce" (the P. glauca × P. engelmannii hybrid) have been reported in the Skeena River area of British Columbia (Sutton et al. 1994).
A 2006 analysis of both paternal and maternal molecular markers (chloroplast and mitochondrial DNA) of all living species of Picea indicated that Picea breweriana and secondarily P. sitchensis are basal to Picea, with the other species in the genus divisible into three clades derived from two episodes of dispersal to Eurasia via the Beringian land bridge (Ran et al. 2006). In this phylogeny, both P. engelmannii and P. glauca equally closely related to P. sitchensis, a result consistent with the hybridization patterns noted above.
Tree to 80 m tall and 500 cm dbh with straight trunk from buttressed base and an open, conical crown of horizontal branches. Bark grey, smooth, thin, becoming dark purplish-brown with scaly plates. Branches somewhat drooping; twigs not or slightly pendent, rather stout, pinkish brown, glabrous, rough, with peglike bases. Buds reddish brown, 5-10 mm, apex rounded. Needles (1.2)1.5-2.5(3) cm, flattened or broadly triangular in cross section (lower surface rounded or slightly angular), rather rigid (painfully sharp), blue-green to light yellow-green, upper surface darker green with stomatal bands very narrow or absent, lower surface glaucous with conspicuous stomatal bands separated by ridge, apex sharp-pointed, dark green, 15-25 mm long. Ovulate cones 5-9 (-10) cm long, cylindrical, short-stalked, green or reddish, ripening pale buff to light orange-brown, pendant from ends of twigs, opening at maturity and falling soon after. Cone scales variable, elliptic to narrowly diamond-shaped, 15-22 × 12-16 mm, rather thin and flexible, margin at apex erose, apex extending 4-8 mm beyond seed-wing impression. 2n=24 (Peattie 1950, Taylor 1993). Bract scale the longest of any spruce, to 7-8 mm long and very occasionally slightly exserted by up to 0.5 mm on basal scales.
Along the northwest coast of North America from Kodiak Island in the western Gulf of Alaska to Mendocino County, California, never more than 200 km from the sea and usually much closer. See also Thompson et al. (1999). USDA hardiness zone 7 (Californian origins zone 8; hybrid P. × lutzii zone 5). Grows at timberline (ca. 1000 m) in Alaska, while remaining below 400 m in California. Typically found in areas with high rainfall and a cool climate, although a considerable range of precipitation and temperature values is encountered across this species' wide latitudinal range. Usually found growing on well-drained acidic soils, in pure stands or with Tsuga heterophylla. Other frequent associates, as they might be encountered traveling from the southern to northern limits of Sitka spruce's range, include the conifers Sequoia sempervirens, Chamaecyparis lawsoniana, Pseudotsuga menziesii, Pinus monticola, Cupressus nootkatensis, Pinus contorta subsp. contorta, Tsuga mertensiana, Picea glauca, and Abies lasiocarpa. An important hardwood associate is Alnus rubra, which often colonizes gravel bars along large rivers at the same time as Sitka spruce (Harris 1990).
Hardy to Zone 7 (cold hardiness limit between -17.7°C and -12.2°C) (Bannister and Neuner 2001).
Sitka spruce is the world's largest spruce (Little 1980), and in terms of wood volume, is the second-largest species in the Pinaceae after Pseudotsuga menziesii. In old growth stands, trees may commonly reach a height of 70 m and diameter of 300 cm. The very largest known specimen (see top photo) grows near road's end in the Queets River valley of Olympic National Park. Bob Van Pelt relates that "Bob Wood first told me about this tree during the late 1980's when I began measuring western trees. He indicated that it had a huge, 15 foot (457 cm) thick trunk, and that it was taller than the tree at Quinault Lake. He also mentioned that a recent study on the growth of this tree indicated that the growth rings are still relatively large, so much so that the tree adds a foot to its circumference every 35 years or so. The implications of this, since the tree has approximately 5,300 ft2 (492 m2) of living cambium, that close to 46 ft3 (4.3 m2) per year are produced by this tree, making it one of the fastest growing trees on the planet!" This tree has a measured diameter of 455 cm and height of 75.6 m, with an estimated wood volume of 337 m3 (Van Pelt 2001).
The second-largest known tree is the San Juan spruce, which grows at a campsite beside the San Juan River on Vancouver Island, a few miles from the largest known tree in the Pinaceae. In fact, the San Juan spruce is the third largest tree in the Pinaceae, with a diameter of 371 cm, a height of 62.5 m, and a wood volume of 333 m3 (Van Pelt 2001).
Neither of these trees is widely known, but at least two other spruces have been proclaimed to be 'the world's largest spruce.' One, a very large specimen near Lake Quinault in Olympic National Forest, WA, has 539 cm dbh due to a large butt swell; it is 58.2 m tall with a wood volume of 298 m3 (Van Pelt 2001). It could be called the world's largest spruce if the only criterion is diameter at a height of 1.4 m, which is sort of like determining the world's largest man by the size of his ankles. The other putative largest tree, near Seaside, OR, fell in a 2006 winter storm. There is debate whether heavy levels of visitor use and construction of a viewing platform around this tree's base contributed to its demise. Certainly, though, the primary cause of its death was extensive stem rot that had been apparent for many years (pers. obs. by C.J. Earle and R. Van Pelt).
The tallest two trees on record, 96.7 m and 96.4 m, are in Prairie Creek Redwoods State Park, California, which is also home to many of the very tallest redwoods (Steve Sillett, pers. comm. 2001.07.14, reporting data collected by Chris Atkins and Michael Taylor, who measured the trees using a survey laser). Third tallest known is the Carmanah Giant, 96.0 m with a dbh of 305 cm, in Pacific Rim National Park in BC (Stoltmann 1993).
In late November 2008, a Sitka spruce was discovered that will definitely be among the largest ones known. This weird-looking tree (photo at left) has a strong lean, with five huge limb systems emerging from the trunk at heights of 7 to 15 m on the uphill side, partly compensating for the lean. At about 30 m height, the main stem divides into four trunks, each of which is over 60 m tall. The DBH is about 365 cm. The average diameter of the crown is more than 36 meters, and the giant limbs support mats of the fern Polypodium scouleri that are among the largest ever recorded (R. Van Pelt, pers. comm. 2008.11.29, and Steve Sillett, e-mail 2008.12.03).
Thought to be 700 or 800 years (Harris 1990), but no supporting data are available.
The sharp needles were believed to give this tree special powers of protection against evil thoughts (though not from chainsaws). Various Northwest Coast peoples have eaten the inner bark or the young shoots; the latter are an excellent source of vitamin C (also much appreciated by the native elk, Cervus canadensis). The pitch was chewed for pleasure and as a medicine for various skin irritations. The roots, peeled, split and dried, were used to make twined, water-tight hats and baskets (Pojar and MacKinnon 1994).
Western society regards Sitka spruce as one of the foremost timber species in its region and also in NW Europe, where it is by far the most widely planted timber tree. The lumber has a high strength-to-weight ratio. It is preferred for acoustic uses such as piano sounding boards and guitar tops and also makes superior ladders, masts, spars, oars, and experimental airplane components including frames and propellers (Harris 1990).
The most famous, and perhaps the best, places to see old growth Sitka spruce forests are the Queets, Hoh and other river valleys of western Olympic National Park (Washington), and Pacific Rim National Park and Carmanah Pacific Provincial Park on Vancouver Island (British Columbia). The former site includes some of the largest spruce, and the latter some of the tallest. See Randy Stoltmann's book, "Hiking the ancient forests of British Columbia and Washington" (1996. Vancouver, BC: Lone Pine) for details on visiting these areas and finding the largest trees.
Together, Sitka spruce and western hemlock dominate one of the great forest types of North America, the coastal forest of the Pacific Northwest. Their native environment is characterized by a cool, moist maritime climate (Franklin 1988).
The most widespread forest disturbance in this environment is windthrow. Severe storms, occurring at intervals of decades to centuries, may flatten entire forests. Wind is also an important chronic disturbance, contributing to about 80% of within-stand mortality in these forests (Franklin 1988). Both spruce and hemlock have adapted to this situation in a distinctive way: their seedlings typically germinate and thrive on a substrate of decaying conifer wood. An old growth spruce-hemlock forest is thus characterized by the presence of "nurse logs," logs that may be covered with seedlings of hemlock and spruce (Kirk and Franklin 1992).
One consequence of life in a cool, moist maritime climate is the development of huge aboveground biomass accumulations, mostly in the form of live and decaying wood. Old growth Sitka spruce-western hemlock forests have been found to have an average aboveground biomass of 1163 tonnes per hectare, a value exceeded only by forests of giant sequoia and redwood (Franklin 1988).
Sitka spruce is also somewhat noteworthy for its tolerance to salt spray, which permits this species to occur on rocky sites along the seashore, sometimes with lodgepole pine, another species tolerant of the salt. Spruce growing in such an environment often show a gnarled and twisted growth form reminiscent of trees growing at timberline. This growth form has been shown to be related to the production of increased amounts of coumarin, a growth hormone widespread among conifers (Löve et al. 1970).
Trees typically begin to produce cones at 15 to 40 years of age. Seeds are small, with an average weight of 2.2 mg. Most seed is dispersed within 6 weeks of initial cone opening, and dispersal is by wind. Trees grow slowly for the first few years after germination but growth then increases rapidly, with heights at 100 years of age ranging from 33 m in Alaska to 48 m in Oregon (Harris 1990); in cultivation in Britain, growth rates of 40 m in 43 years, and 60 m in 110 years, are recorded on the best sites (A F Mitchell).
This is one of the conifer species that can produce epicormic branches. If a stand is opened up to light, for instance by an adjacent clearcut, new branches may originate along the exposed tree trunks (Harris 1990).
Sitka spruce is the state tree of Alaska (Harris 1990).
Jill A. Hamilton and Sally N. Aitken. 2013. Genetic and morphological structure of a spruce hybrid (Picea sitchensis × P. glauca) zone along a climatic gradient. American Journal of Botany 100(8):1651-1662.
B. C. S. Sutton, S. C. Pritchard, J. R. Gawley, C. H. Newton, and G. K. Kiss. 1994. Analysis of Sitka spruce–interior spruce introgression in British Columbia using cytoplasmic and nuclear DNA probes. Canadian Journal of Forest Research 24(2):278-285.
This page co-edited with Michael P. Frankis, 1998.12.
Daubenmire, R. 1968. Some geographic variations in Picea sitchensis and their ecologic interpretation. Canadian Journal of Botany 46:787-798.
Last Modified 2013-12-10