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The blue spruce (''Picea pungens''), also commonly known as green spruce, Colorado spruce, or Colorado blue spruce, is a
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
of spruce tree. It is
native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...
to North America, and is found in USDA growing zones 1 through 7. It is found naturally in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming. It has been widely introduced elsewhere and is used as an ornamental tree in many places far beyond its native range. The blue spruce has blue-green colored needles and is a
coniferous 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 extan ...
tree.


Description

In the wild, ''Picea pungens'' grows to about , but when planted in parks and gardens it seldom exceeds tall by 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 long, are arranged radially on the shoots which curve upwards. The pale brown cones are up to long.USDA
Accessed 2012-12-01
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 Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, bird ...
. The specific epithet ''pungens'' means "sharply pointed", referring to the leaves. The blue spruce is the state tree of
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 ...
.


Cultivation

''Picea pungens'' and its many cultivars are often grown as ornamental trees in gardens and parks. It is also grown for the
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 ...
industry.


Pests and diseases

The blue spruce is attacked by two species of ''
Adelges ''Adelges'' is a genus of insects which feed on conifers. Excepting galls formed by the spruce gall midge, galls are caused by aphid-like insects of the superfamily Phylloxeroidea (family Adelgidae) commonly known as the spruce gall adelgids. ...
'', an aphid-like insect that causes galls to form.
Nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
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 ''Choristoneura'' is a genus of moths in the family Tortricidae. Several species are serious pests of conifers, such as spruce and are known as spruce budworms. Species *'' Choristoneura adumbratanus'' (Walsingham, 1900) *'' Choristoneura afr ...
eat the buds and growing shoots while the
spruce needle miner A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ( taiga) regions of the Earth. ''Picea'' is the sole genus in the subfam ...
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 Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...
, 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'', the spruce beetle, is a species of bark beetle native to British Columbia, Newfoundland and Labrador, Nova Scotia, Ontario, Quebec, Northern Manitoba, the Yukon, Colorado, Wyoming, Montana, and Maine. They are known ...
(''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 ''Cytospora'' is a genus of ascomycete fungi. The genus was first described in 1818 by Christian Gottfried Ehrenberg.Ehrenberg, C.G. (1818''Sylvae mycologicae Berolinenses'' 40 as ''Cytispora'' ''Cytospora'' species are known as plant pathogens ...
'' 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.


Rooting habits

Blue spruce seedlings have shallow roots that penetrate only 6.4 cm (2.5 inches) of soil during the first year. Although freezing can't damage much in blue spruce, frost 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.


Cultivars

Common cultivars (those marked have gained the Royal Horticultural Society's
Award of Garden Merit The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. History The Award of Garden Merit ...
): *'Glauca Globosa' – shrub from in height *'Fat Albert' – compact perfect cone to of a silver blue color *'Glauca Jean's Dilly' – shrub from in height *'Glauca Pendula' – drooping branches, spreads to about wide by tall *'Hoopsii' *'Koster' *'Baby Blue Eyes' *'Baby Blue'


Uses

The Navajo and
Keres In Greek mythology, the Keres (; Ancient Greek: Κῆρες), singular Ker (; Κήρ), were female death-spirits. They were the goddesses who personified violent death and who were drawn to bloody deaths on battlefields. Although they were pre ...
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 defense and protection ag ...
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.


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


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.


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. And fifth 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.


References


External links


Conifers.org: Picea pungens (blue spruce) descriptionLady Bird Johnson Wildflower Center NPIN
— Native Plant Information Network
Interactive Distribution Map of ''Picea pungens''

''Picea pungens''
— U.C. Photo Gallery {{Authority control Picea Trees of North America Trees of Canada Trees of the United States Trees of the Western United States Trees of the South-Central United States Trees of the Southwestern United States Flora of the Rocky Mountains Least concern flora of the United States Symbols of Colorado Plants used in traditional Native American medicine Garden plants of North America Ornamental trees Plants described in 1879