Blue spruce

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Colorado blue spruce
Picea pungens tree.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Pinaceae
Genus: Picea
Species:
P. pungens
Binomial name
Picea pungens
Picea pungens range map.png

The blue spruce (Picea pungens), also commonly known as green spruce, [2] Colorado spruce, or Colorado blue spruce, is a species of spruce tree native to North America in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming. [3] 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. [4]

Contents

Description

In the wild, Picea pungens grows to about 23 m (75 ft), but when planted in parks and gardens it seldom exceeds 15 m (49 ft) tall by 5 m (16 ft) wide. The tree can grow larger if the tip is cut when it is at least 3 years old. It is a columnar or conical evergreen conifer with densely growing horizontal branches. It has scaly grey bark on the trunk with yellowish-brown branches.

Waxy gray-green leaves, up to 3 cm (1 in) long, are arranged radially on the shoots which curve upwards. The pale brown cones are up to 10 cm (4 in) long. [5] [6] [7] [8] Male cones are found on the entire tree, whereas the female cones are found at the top of the tree. This helps to facilitate cross-pollination. [9]

The specific epithet pungens means "sharply pointed", referring to the leaves. [10]

Ecology

Blue Spruce occurs at high elevation (above 6000 ft/1830m) in the Rocky Mountains of the west-central United States. It grows in mesic montane conifer forests, often associating with Douglas-fir, ponderosa pine, or white fir. It has a riparian affinity. [4]

Climate

Blue spruce usually grows in cool and humid climatic zones where the annual precipitation mainly occurs in the summer. [11]

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. [12] [13]

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. And fifth percent[ dubious ] of the annual precipitation occurs during the growing season of the plants. [12] [14]

Blue spruce is generally considered to grow best with abundant moisture. Nevertheless, this species can withstand drought better than any other spruce. [15] 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. [11]

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. [16]

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. [16] [17] [18]

Blue spruce is considered as a pioneer tree species in moist soil in Utah. [19]

Rooting habits

Blue spruce seedlings have shallow roots that penetrate only 6.4 cm (2.5 inches) of soil during the first year. [20] Although freezing can't damage much in blue spruce, frost heaving will cause seedling loss. Shadows in late spring and early autumn minimize this frost heaving loss. [21] [22] Despite the shallow roots, blue spruce is able to resist strong winds. [23] 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. [24]

Pests and diseases

The blue spruce is attacked by two species of Adelges , an aphid-like insect that causes galls to form. Nymphs of the pineapple gall adelgid 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, 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. [25] [26] 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. [27]

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 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 appear on the bark and the branch eventually dies. [25]

Cultivation

'Mission Blue' blue spruce new growth in spring 2015-05-18 13 01 32 Blue Spruce new growth along Terrace Boulevard in Ewing, New Jersey.jpg
'Mission Blue' blue spruce new growth in spring

Picea pungens and its many cultivars are often grown as ornamental trees in gardens and parks. [6] [7] [28] It is also grown for the Christmas tree industry. [6] It grows best in USDA growing zones 1 through 7, [29] though it also does well in zones warmer than 7 where summer heat is moderate, as at San Francisco. [30]

Common cultivars (those marked agm have gained the Royal Horticultural Society's Award of Garden Merit): [31]

Foliage of the cultivar 'Glauca globosa' Picea pungens 'Glauca globosa' in Autumn.JPG
Foliage of the cultivar 'Glauca globosa'

Culture

The Navajo and Keres Native Americans use this tree as a traditional medicinal plant 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. Early people used their wood for building. [42]

The blue spruce is the state tree of Colorado. [43]

See also

Related Research Articles

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The Douglas fir is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three varieties: coast Douglas-fir, Rocky Mountain Douglas-fir and Mexican Douglas-fir.

<span class="mw-page-title-main">Conifer</span> Group of cone-bearing seed plants

Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta, also known as Coniferophyta or Coniferae. The division contains a single extant class, Pinopsida. All extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs. Examples include cedars, Douglas-firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 2002, Pinophyta contained seven families, 60 to 65 genera, and more than 600 living species.

<span class="mw-page-title-main">Spruce</span> Genus of evergreen, coniferous tree

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<i>Picea mariana</i> North American species of spruce tree

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<i>Picea abies</i> Species of plant

Picea abies, the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe.

<i>Pinus wallichiana</i> Species of conifer

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<i>Picea sitchensis</i> Species of large coniferous tree

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<i>Picea omorika</i> Species of conifer

Picea omorika, common name Pančić spruce or Serbian spruce, is a species of coniferous tree endemic to the Drina River valley in western Serbia, and eastern Bosnia and Herzegovina, with a total range of only about 60 ha, at 800–1,600 m (2,625–5,249 ft) altitude. It was originally discovered near the Serbian village of Zaovine, on Mount Tara, in 1875, and named by the Serbian botanist Josif Pančić; the specific epithet omorika is simply the Serbian word for the tree.

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<i>Abies concolor</i> Species of conifer tree

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 into the isolated mountain ranges of southern Arizona, New Mexico, and Northern Mexico. It naturally occurs at elevations between 900 and 3,400 metres.

<i>Tsuga heterophylla</i> Species of conifer

Tsuga heterophylla, the western hemlock or western hemlock-spruce, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California. The Latin species name means 'variable leaves'.

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<i>Picea glauca</i> Species of conifer

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<i>Picea engelmannii</i> Species of North American spruce tree

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-elevation mountain tree but also appears in watered canyons.

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<i>Arceuthobium pusillum</i> Species of dwarf mistletoe

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