''Picea engelmannii'', with the common names Engelmann spruce, white spruce, mountain spruce, and silver spruce, is a species of spruce native to western North America. It is mostly a high-altitude mountain tree but also appears in watered canyons.

Description

''Picea engelmannii'' is a medium-sized to large evergreen tree growing to tall, exceptionally to tall, and with a trunk diameter of up to . The reddish

bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, e ...

is thin and scaly, flaking off in small circular plates 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 A pulvinus (pl. ''pulvini'') is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvini are common, for example, in members of the bean family Fabaceae (Leguminosae) and the prayer plant ...

. The

leaves A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

are needle-like, long, flexible, 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 needles have a pungent odour when crushed. Purple

cones A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...

of about 1 cm appear in spring, releasing yellow pollen when windy. The cones are pendulous, slender cylindrical, 2.5–8 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 to light brown 4–7 months after pollination. The seeds are black, 2–3 mm long, with a slender, 5–8 mm long light brown wing. The tree grows in a '' krummholz'' form along the fringe of alpine tundras.

Distribution

Engelmann spruce is native to western North America, primarily in the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

and east slopes of the

Cascade range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

from central British Columbia to Southern Oregon in the Cascades and commonly in Montana,

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyomi ...

, and

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

, and more sparsely towards Arizona and New Mexico in the

Sky islands Sky islands are isolated mountains surrounded by radically different lowland environments. The term originally referred to those found on the Mexican Plateau, and has extended to similarly isolated high-elevation forests. The isolation has ...

; there are also two isolated populations in

Northern Mexico Northern Mexico ( es, el Norte de México ), commonly referred as , is an informal term for the northern cultural and geographical area in Mexico. Depending on the source, it contains some or all of the states of Baja California, Baja California ...

. It is mostly a high-altitude mountain tree, in many areas reaching the tree line, but at lower elevations occupies cool watered canyons. It grows from above sea level, rarely lower towards the northwest. It appears in the canyons of the Idaho Panhandle and more limitedly in the northeastern Olympic Mountains; the latter includes exceptionally large specimens, e.g. one thick and tall. It can be found in the

Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

(mostly on the eastern slopes) from elevations of and liberally in the

. It can also be found in the

Monashee The Monashee Mountains are a mountain range lying mostly in British Columbia, Canada, extending into the U.S. state of Washington. They stretch from north to south and from east to west. They are a sub-range of the Columbia Mountains. The high ...

and

Selkirk Mountains The Selkirk Mountains are a mountain range spanning the northern portion of the Idaho Panhandle, eastern Washington, and southeastern British Columbia which are part of a larger grouping of mountains, the Columbia Mountains. They begin at Mica ...

, as well as the highlands surrounding the Interior Plateau.

Ecology

Both water uptake and water stored in roots appear to be critical for the survival of subalpine Engelmann spruce saplings that are exposed above the snowpack in later winter to early spring.Boyce, R.L. and Lucero, S.A. 1999. Role of roots in winter water relations of Engelmann spruce saplings. Tree Physiol. 19:893–898. Transpiration is greatly reduced in small saplings while engulfed in snowpack. For exposed trees, the availability of soil water may be critical in late winter, when transpirational demands increase. Increased rates of transpiration in response to loss of snowpack, coupled with low sapwood water reserves and an extended period of soil frost in windswept areas, may prevent Engelmann spruce from regenerating in open areas both above and below the tree line. Cuticular damage by windblown ice is probably more important at the tree line,Hadley, J.L.; Smith, W.K. 1983. Influence of wind exposure on needle desiccation and mortality for timberline conifers in Wyoming, USA. Arctic Alpine Res. 15:127–135. (Cited in Coates et al. 1994).Hadley, J.L.; Smith, W.K. 1986. Wind effects on needles of timberline conifers seasonal influence on mortality. Ecology 67:12–19. Cited in Coates et al. (1994). but damage caused by desiccation is likely to be more important at lower elevations. Despite wind damage, the species tends to grow taller than others at the tree line. It is shade tolerant, but not so much as

subalpine fir ''Abies lasiocarpa'', the subalpine fir or Rocky Mountain fir, is a western North American fir tree. Description ''Abies lasiocarpa'' is a medium-sized evergreen conifer with a very narrow conic crown, growing to tall, exceptionally , with a t ...

. Thus, it is somewhat dependent on fires to outgrow competitors, although its thin bark and shallow roots make it vulnerable to fire as well. Spruce bark beetles attack the tree, being particularly deadly to groups which have stood for centuries. It is also susceptible to avalanches. Although older spruce forests are not very useful to animals for forage, they are so in the aftermath of fires, which allow many other plants to rise. Engelmann spruce-shaded streams are exploited by trout. Additionally,

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

s produce galls which hang from the tree and look similar to cones when they dry out.

Subspecies and hybrids

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 Coahuila (), formally Coahuila de Zaragoza (), officially the Free and Sovereign State of Coahuila de Zaragoza ( es, Estado Libre y Soberano de Coahuila de Zaragoza), is one of the 32 states of Mexico. Coahuila borders the Mexican states of Nu ...

(

Sierra Madre Oriental The Sierra Madre Oriental () is a mountain range in northeastern Mexico. The Sierra Madre Oriental is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that ...

) and on Cerro Mohinora in

Chihuahua Chihuahua may refer to: Places * Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mu ...

(

Sierra Madre Occidental The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American Co ...

). Engelmann spruces of the

Madrean sky islands The Madrean Sky Islands are enclaves of Madrean pine–oak woodlands, found at higher elevations in a complex of small mountain ranges in southern and southeastern Arizona, southwestern New Mexico, and northwestern Mexico. The sky islands are sur ...

mountains in the extreme southeast of Arizona and southwest of New Mexico also probably belong to this subspecies, though this is disputed. The Engelmann spruce hybridises and intergrades extensively with the closely related white spruce (''

Picea glauca ''Picea glauca'', the white spruce, is a species of spruce native to the northern temperate and boreal forests in North America. ''Picea glauca'' is native from central Alaska all through the east, across southern/central Canada to the Avalon Pe ...

''), found further north and east in the Rockies, and to a lesser extent with the closely related

Sitka spruce ''Picea sitchensis'', the Sitka spruce, is a large, coniferous, evergreen tree growing to almost tall, with a trunk diameter at breast height that can exceed 5 m (16 ft). It is by far the largest species of spruce and the fifth-larg ...

where they meet on the western fringes of the Cascades.

Uses

Native Americans made various medicines from the resin and foliage. Engelmann spruce is of economic importance for its wood, being light and fairly strong. It harvested for paper-making and general construction. Wood from slow-grown trees at high altitude has a specialised use in making musical instruments such as acoustic guitars, harps, violins, and pianos. Because it is odourless and has little resin, it has been used for food containers such as barrels. It is also used to a small extent as a

Christmas tree A Christmas tree is a decorated tree, usually an evergreen conifer, such as a spruce, pine or fir, or an artificial tree of similar appearance, associated with the celebration of Christmas. The custom was further developed in early modern G ...

Gallery

File:Picea engelmannii Sierra Blanca NM.jpg, Young tree File:Engelmann spruce below Boulder Pond Payette NF.jpg, Forest floor under Engelmann spruces File:Picea engelmannii foliage cones.jpg, Forest, with mature female cones in foreground File:Picea engelmannii UGA1.jpg, Dangling somewhat immature (unopened) female cone File:Picea engelmannii UGA2.jpg, Dangling mature female cone File:Engelmann Spruce cones RMNP.jpg, Purple immature cones and yellow mature cones from the previous year. No male pollen cones are visible; the brownish-golden branch tips are protective bud scales being shed from the spruce buds

References

External links

Jepson Manual Treatment
– Photographs related spruce cones
CalPhotos
{{Authority control engelmannii Trees of the Western United States Trees of Western Canada Trees of the West Coast of the United States Trees of Northwestern Mexico Trees of Chihuahua (state) Trees of Coahuila Trees of the Northwestern United States Trees of the Southwestern United States Trees of the South-Central United States Flora of the Cascade Range Flora of the Klamath Mountains Flora of the Rocky Mountains Alpine flora Least concern flora of the United States Taxa named by George Engelmann Taxa named by Charles Christopher Parry Flora of the Sierra Madre Occidental