Picea engelmannii

Picea engelmannii

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Picea engelmannii

Picea engelmannii (Engelmann Spruce) is a species of spruce native to western North America, from central British Columbia and southwest Alberta, southwest to northern California and southeast to Arizona and New Mexico; there are also two isolated populations in northern Mexico. It is mostly a high altitude mountain tree, growing at 900-3650 m altitude, rarely lower in the northwest of the range; in many areas it reaches the alpine tree line.

Foliage

It is a medium-sized to large evergreen tree growing to 25-40 m tall, exceptionally to 65 m tall, and with a trunk diameter of up to 1.5 m. The bark is thin and scaly, flaking off in small circular plates 5-10 cm across. The crown is narrow conic in young trees, becoming cylindric in older trees. The shoots are buff-brown to orange-brown, usually densely pubescent, and with prominent pulvini. The leaves are needle-like, 15-30 mm long, rhombic in cross-section, glaucous blue-green above with several thin lines of stomata, and blue-white below with two broad bands of stomata.

The cones are pendulous, slender cylindrical, 4-8 cm long and 1.5 cm broad when closed, opening to 3 cm broad. They have thin, flexible scales 15-20 mm long, with a wavy margin. They are reddish to dark purple, maturing pale brown 4-7 months after pollination. The seeds are black, 2-3 mm long, with a slender, 5-8 mm long pale brown wing.

Two geographical subspecies (treated as varieties by some authors, and as distinct species by others) occur:

Picea engelmannii subsp. engelmannii (Engelmann Spruce). All of the range except as below.
Picea engelmannii subsp. mexicana (Mexican Spruce). Two isolated populations on high mountains in northern Mexico, on the Sierra del Carmen in Coahuila (Sierra Madre Oriental) and on Cerro Mohinora in Chihuahua (Sierra Madre Occidental). Engelmann Spruces of the Madrean sky islands mountains in the extreme southeast of Arizona and southwest of New Mexico also probably belong to this subspecies, though this is disputed.

Engelmann Spruce hybridises and intergrades extensively with the closely related White Spruce found further north and east in the Rocky Mountains, and to a lesser extent with the closely related Sitka Spruce where they meet on the western fringes of the Cascades.

Uses

Engelmann Spruce is of economic importance for its wood, harvested for paper-making and general construction. Wood from slow-grown trees at high altitude has a specialised use in making acoustic guitars and harps. It is also used to a small extent as a Christmas tree.