The blue spruce (''Picea pungens''), also commonly known as Colorado spruce or Colorado blue spruce, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...

tree native to North America in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming. It is noted for its blue-green colored needles, and has therefore been used as an ornamental tree in many places far beyond its native range.

Description

In the wild, ''Picea pungens'' grows to as much as in height, but more typically tall. When planted in parks and gardens it most often grows tall with a spread of . It has scaly grey-brown bark with a slight amount of a cinnamon-red undertone on its trunk, not as rough as an

Engelmann spruce ''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 highly prized for producing distinctive tone wood for acoustic guitars ...

. On older trees the trunk bark will be deeply furrowed and scaly. The diameter of the trunk may reach as much as . Blue spruces are

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

s with a pyramidal or conical

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

when young, but more open and irregular in shape as they become older. The stout branches grow out horizontally in well defined whorls, but lower branches droop downwards as trees age. Young twigs never hang downwards and are yellow-brown in color. The narrow, needle-like,

evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

leaves are quite sharply pointed and may be dull green, blue, or pale white. Each of the needles is four sided with

stomata In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...

on every side, stiff, and long. The needles are attached radially to their shoots, but curve upward. The leaf buds are golden brown and cone shaped. The buds may be in size and the tip may either be blunt or pointed. The pollen producing cones, more properly strobili, develop throughout the crown of blue spruce trees, but are more common in the upper half of the crown. Pollen cones are mainly yellow with a touch of red and average long. The seed cones begin growing in May or June and release their mature seeds in the autumn of the same year in which they start to grow. When young they are purple-brown in color. When fully mature they are light brown with thin, papery scales and are often curved. Overall they are longer than they are wide, between long, and circular in cross section. The seed cones are only found at the top of the tree. This helps to facilitate cross-pollination. Picea pungens seeds

The seeds are dark brown. They average 4 mm in length with the papery wing extending beyond the tip almost twice this length.

Chemistry

The

phytochemistry Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and ...

of the blue spruce is relatively little studied. The ripe seeds have a 1.17% yield of essential oils while the cones produce only 0.38% when steam distilled for four hours. The main component, over 40%, of the essential oils is

limonene Limonene () is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the essential oil of citrus fruit peels. The (+)-isomer, occurring more commonly in nature as the fragrance of oranges, ...

with β-Pinene and α-Pinene the next most significant.

Taxonomy

''Picea pungens'' was given its first valid scientific description by

George Engelmann George Engelmann, also known as Georg Engelmann, (2 February 1809 – 4 February 1884) was a German-American botanist. He was instrumental in describing the flora (plants), flora of the west of North America, then very poorly known to Europeans; ...

in 1879. He had previously named it ''Abies menziesii'' in 1862 and later as ''Picea menziesii'' in 1863, but both those names had already been used making them illegitimate names.

Names

''Picea'', the genus name, is thought to come from the Latin word ''pix'' meaning "pitch", a reference to the typical sticky resin in spruce bark. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''pungens'' means "sharply pointed", referring to the leaves. The most frequently used

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

in English is ''blue spruce''. It was first used for other trees in 1817 and is still used for any spruce tree with a glaucous blue color to their needles, but most frequently meaning ''Picea pungens''. Though this is the most common name, in the wild only part of the population has the waxy blue-gray coating for which the tree is named. Less frequently, but still common, is ''Colorado blue spruce'', a name first used in 1912. The usage of ''Colorado spruce'' dates to 1881, but is less frequent than the longer alternate. Occasionally encountered are the names ''Parry's spruce'', ''prickly spruce'', ''silver spruce'', and ''white spruce''. Blue spruces are also rarely called ''silvertip fir'', but this name is also applied to ''

Abies magnifica ''Abies magnifica'', the red fir or silvertip fir, is a western North American fir, native to the mountains of southwest Oregon and California in the United States. It is a high-elevation tree, typically occurring at elevation, though only rare ...

'' especially when sold as Christmas trees. In addition it is sometimes labeled as "Colorado green spruce" or "green spruce" by plant nurseries or tree farms. Similar to the meaning of the scientific name, the

Navajo The Navajo or Diné are an Indigenous people of the Southwestern United States. Their traditional language is Diné bizaad, a Southern Athabascan language. The states with the largest Diné populations are Arizona (140,263) and New Mexico (1 ...

name for this species is a compound ''c’ó deniní'' with c’ó meaning spruce and deniní meaning "it is sharp".

Ecology

Blue Spruce occurs at high elevations, in the forests of the South Central Rockies and in the

Southern Rocky Mountains The Southern Rocky Mountains are a major subregion of the Rocky Mountains of North America located in the southeastern portion of the U.S. state of Wyoming, the central and western portions of Colorado, the northern portion of New Mexico, and ext ...

. It grows in mesic montane conifer forests, often associating with

Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is the tallest tree in the Pinaceae family. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Or ...

ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine, is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is t ...

, or

white fir ''Abies concolor'', the white fir, concolor fir, or Colorado fir, is a coniferous tree in the pine family Pinaceae. This tree is native to the mountains of western North America, including the Sierra Nevada and southern Rocky Mountains, and int ...

. It has a

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

affinity, preferring moist soils such as those along streams or at the edges of wet meadows. The Douglas-fir or ponderosa pine only become associated with streams at lower, warmer elevations. It also may be found alongside the

quaking aspen ''Populus tremuloides'' is a deciduous tree native to cooler areas of North America, one of several species referred to by the common name aspen. It is commonly called quaking aspen,

(''Populus tremuloides'') in the high mountain habitats of desert ranges in the Intermountain West.

Climate

Blue spruce usually grows in cool and humid climatic zones where the annual precipitation mainly occurs in the summer. Blue spruce is most common in Colorado and the Southwest. The annual average temperature ranges from 3.9 to 6.1 degrees C (39 to 43 degrees F). And ranges from - 3.9 to - 2.8 degrees C (25 to 27 degrees F) in January. In July, the average temperature ranges from 13.9 to 15.0 degrees C (57 to 59 degrees F). The average minimum temperature in January ranges from - 11.1 to 8.9 degrees C (12 to 16 degrees F), and the average maximum temperature in July ranges from 21.1 to 22.2 C (70 to 72 degrees F). There is a frost-free period of about 55 to 60 days from June to August. Annual mean precipitation generally vary from 460 to 610 mm (18 to 24 in). Winter is the season with the poorest rainfall, the precipitation is usually less than 20 percent of the annual moisture falling from December to March. Fifty percent of the annual precipitation occurs during the growing season of the plants. Blue spruce is generally considered to grow best with abundant moisture. Nevertheless, this species can withstand drought better than any other spruce. It can withstand extremely low temperatures (-40 degrees C) as well. Furthermore, this species is more resistant to high insolation and frost damage compared to other associated species.

Distributed soil types and topography

Blue spruce generally exists on gentle uplands and sub irrigated slopes, in well-watered tributary drainage, extending down intermittent streams, and on lower northerly slopes. Blue spruce always grow naturally in the soils which are in the order Mollisols, and the soil will also be in the orders histosols and inceptisols in a lesser extent. Blue spruce is considered as a pioneer tree species in moist soil in Utah.

Rooting habits

Blue spruce seedlings have shallow roots that penetrate approximately into the soil during the first year of growth. Although freezing can't damage much in blue spruce,

frost heaving Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated int ...

will cause seedling loss. Shadows in late spring and early autumn minimize this frost heaving loss. Despite the shallow roots, blue spruce is able to resist strong winds. Five years before transplanting, the total root surface area of 2-meter-high trees was doubled by pruning the roots of blue spruce. It also increases the root concentration in drip irrigation pipeline from 40% to 60%, which is an advantage in landscape greening.

Pests and diseases

The blue spruce is attacked by two species of ''

Adelges ''Adelges'' is a genus of insects which feed on conifers. They have complex life cycles, some species feeding exclusively on spruce, others feeding on spruce and an alternate Pinophyta, conifer. However, galls characteristic of each species are ...

'', an aphid-like insect that causes galls to form.

Nymphs A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

of the

pineapple gall adelgid The pineapple gall adelgid (''Adelges abietis'') is a species of conifer-feeding insect that forms pineapple-shaped plant galls on its host species, commonly Norway and Sitka spruce. The adelgids (genus ''Adelges'') are pear-shaped, soft-bodie ...

form galls at the base of twigs which resemble miniature pineapples and those of the Cooley's spruce gall adelgid cause cone-shaped galls at the tips of branches. The larva of the spruce budworm eat the buds and growing shoots while the spruce needle miner hollows out the needles and makes them coalesce in a webbed mass. An elongated white

scale insect Scale insects are small insects of the Order (biology), order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient g ...

, the pine needle scale feeds on the needles causing fluffy white patches on the twigs and aphids also suck sap from the needles and may cause them to fall and possibly dieback. Mites can also infest the blue spruce, especially in a dry summer, causing yellowing of the oldest needles. Another insect pest is the spruce beetle (''Dendroctonus rufipennis'') which bores under the bark. It often first attacks trees which have blown over by the wind and when the larvae mature two years afterwards, a major outbreak occurs and vast numbers of beetles attack nearby standing trees. The blue spruce is susceptible to several needle casting diseases which cause the needles to turn yellow, mottled or brown before they fall off. Various rust diseases also affect the tree causing yellowing of the needles as well as needle fall.

Canker A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...

caused by '' Cytospora'' attacks one of the lower branches first and progressively makes its way higher up the tree. The first symptom is the needles turning reddish-brown and falling off. Meanwhile, patches of white

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

appear on the bark and the branch eventually dies. It is also relatively intolerant of light pollution and when planted near street lights or other outdoor lighting its preparation for winter can be delayed and parts of the tree may be damaged.

Range

The native range of the blue spruce is largely in the Central and

and moist mountain valleys and canyons to the west. In New Mexico it only grows naturally in the higher mountain ranges of the state such as the Sandia–Manzano Mountains,

Sangre de Cristo Mountains The Sangre de Cristo Mountains (Spanish language, Spanish for "Blood of Christ") are the southernmost mountain range, subrange of the Rocky Mountains. They are located in southern Colorado and northern New Mexico in the United States. The mountai ...

, and

San Juan Mountains The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized (the Colorado Mineral Belt) and figured in the gold and silver mining industry ...

, as well as on Sierra Blanca Peak to the south. In Arizona the range is even more limited, growing in just Coconio and

Apache The Apache ( ) are several Southern Athabaskan language-speaking peoples of the Southwestern United States, Southwest, the Southern Plains and Northern Mexico. They are linguistically related to the Navajo. They migrated from the Athabascan ho ...

counties. In Apache County it is found in the White Mountains in central eastern Arizona and the Lukachukai Mountains in the northeastern corner of the state. In Coconino County they only grow on the Kaibab Plateau. The blue spruce grows in every county in the western two-thirds of Colorado; approximately half of natural range of the species is in the mountains of Colorado. In Utah they are a locally common part of forests in the

Uinta Mountains The Uinta Mountains ( ) are an east-west trending mountain range in northeastern Utah extending a short distance into northwest Colorado and slightly into southwestern Wyoming in the United States. As a subrange of the Rocky Mountains, they are u ...

. West of the Uintas blue spruces are less frequent in canyons south of Salt Lake City. The blue spruce has become

naturalized Naturalization (or naturalisation) is the legal act or process by which a non-national of a country acquires the nationality of that country after birth. The definition of naturalization by the International Organization for Migration of the ...

outside of its native range. In North America has escaped from cultivation in the states of Minnesota and New York. It has also become established to some extent in many western and northern European countries including Iceland, Norway, Sweden, the United Kingdom, France, and Belgium. In middle and southern Europe it is found in Germany, Switzerland, Austria, the former Czechoslovakia, and mainland Italy. To the east it grows in European portions of Russia, the Caucasus, and Bulgaria.

Notable trees

The tallest documented blue spruce tree is an individual in the

of southern Colorado in the Hermosa Creek area. When measured by Matt Markworth in 2015 it was tall. Just three years later in 2018 it was threatened by the 416 Fire. Though the fire killed a shorter American champion tree with a larger trunk and crown spread the tall tree was spared due to being located in a sheltered valley.

Cultivation

''Picea pungens'' and its many

cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...

s are often grown as

ornamental tree Ornamental plants or ''garden plants'' are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars th ...

s in gardens and parks. It is also grown for the

Christmas tree A Christmas tree is a decorated tree, usually an evergreen pinophyta, conifer, such as a spruce, pine or fir, associated with the celebration of Christmas. It may also consist of an artificial tree of similar appearance. The custom was deve ...

industry. It grows best in USDA growing zones 1 through 7, though it also does well in zones warmer than 7 where summer heat is moderate, as at

San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

. Common cultivars (those marked have gained the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...

Award of Garden Merit The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. It includes the full range of cultivated p ...

): *'Baby Blue Eyes', 'Baby Blueeyes', or 'Baby Blue' – This is a semi-dwarf cultivar that grows slowly, but may eventually reach in height. It has a pyramidal shape and holds its color well. *'Fat Albert' – compact perfect cone to of a silver blue color *'Globosa' – shrub from in height *'Hoopsii' – A full size variety with a dense pyramidal habit known for "excellent" silver-blue color of its foliage. It reaches tall when full grown. *'Koster' – A medium sized cultivar that will reach *'Montgomery' – a slow growing dwarf variety. It will typically only grow tall in eight years, but may eventually reach a height of over . *'Pendula' – drooping branches, spreads to about wide by tall *'Sester's Dwarf' – denser foliage than the species, slowly grows to about tall

Culture

The

and Keres Native Americans use this tree as a traditional

medicinal plant Medicinal plants, also called medicinal herbs, have been discovered and used in traditional medicine practices since prehistoric times. Plants synthesize hundreds of chemical compounds for various functions, including Plant defense against h ...

and a ceremonial item, and twigs are given as gifts to bring good fortune. In traditional medicine, an infusion of the needles is used to treat colds and settle the stomach. This liquid is also used externally for rheumatic pains. The blue spruce is the state tree of

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. It officially became Colorado's state tree on 7 March 1939 when House Joint Resolution 7 was enacted by the legislature. Previously a vote of the state's school children was taken on

Arbor Day Arbor Day (or Arbour Day in some countries) is a Secularity, secular day of observance in which individuals and groups are encouraged to plant trees. Today, many countries observe such a holiday. Though usually observed in the spring, the date v ...

in 1892 expressing their preference for the blue spruce as the state tree. From 1933 until 2014 the blue spruce was also the state tree of Utah. It was replaced by the

quaking aspen ''Populus tremuloides'' is a deciduous tree native to cooler areas of North America, one of several species referred to by the common name aspen. It is commonly called quaking aspen,

because the aspen is a great deal more common than the blue spruce in Utah, making up 10% of the state's tree cover.

Gallery

File:Picea pungens Žilina.JPG, Mature tree File:Picea pungens2.jpg, Mature cone File:Picea Pungens Young Cones.jpg, Immature cone File:Picea_pungens_Hoopsii201601.jpg, Hoopsii File:Picea pungens 'Koster' Lappen nursery.jpg, Koster File:Picea pungens Globosa2.jpg, Globosa File:Picea pungens 'Montgomery' 2006-05-03.jpg, Montgomery File:Fat Albert Colorado spruce.jpg, Fat Albert

Citations

References

; Books * * * * * * * * * * * * * * * * * *

External links

Conifers.org: Picea pungens (blue spruce) description

Lady Bird Johnson Wildflower Center NPIN
��Native Plant Information Network
Interactive Distribution Map of ''Picea pungens''

''Picea pungens''
��U.C. Berkeley Photo Gallery {{Authority control Flora of Arizona Flora of Colorado Flora of Idaho Flora of Montana Flora of New Mexico Flora of Utah Flora of Wyoming Picea Plants described in 1879 Symbols of Colorado Trees of Northern America