Blue spruce

The blue spruce, also commonly known as 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. It is noted for its often strongly glaucous blue-green 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 gray-brown bark with a slight amount of a cinnamon-red undertone on its trunk, not as rough as an Engelmann spruce. On older trees the trunk bark becomes deeply furrowed and scaly. The trunk diameter may reach as much as. The root system is of the blue spruce is dense and compact, lacking a taproot.
Blue spruce is a conifer with a conical crown when young, but more open and irregular in shape as it becomes 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 leaves are quite sharply pointed and may be dull green, blue, or pale white. The white or blue glaucous color is caused by surface waxes on the needles and is most visible on newly emerging foliage and fades towards summer. In the wild stands of trees tend to have similar coloration. Each of the needles is four sided with stomata 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, longer than they are wide, circular in cross section with thin, papery scales and can be curved or straight. The cones can measure between long, but are more typically. The seed cones are only found in the top tenth to quarter of the tree and are normally near the end of side branches.
The seeds are dark brown. They average 4 mm in length with the papery wing extending beyond the tip almost twice this length.
The blue spruce can be confused with four other spruce species, Engelmann spruce, European spruce, white spruce, however only the range of the Engelmann spruce overlaps with the blue spruce in the wild. Though larger for the blue spruce, the measurements of their cones and cone scales overlap with the Engelmann spruce. The cones of the Engelmann measuring 3–8 cm with the scales measuring 3–8 mm beyond the seed impression while the blue spruce measures 5–12 cm with scales that measure 8–10 mm beyond the seed impression. However, the twigs of the Engelman are always finely hairy while those of the blue are usually hairless.

Chemistry

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

Taxonomy

Picea pungens was given its first valid scientific description by George Engelmann 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. The specimens of the tree used to describe it were collected by Charles Christopher Parry on Pikes Peak, also in 1862.
There was confusion regarding the correct scientific name for the species during the late 1800s and early 1900s with Picea parryana believed by many to be the correct name, though with various authorities attached to it. This was caused by the 1876 description of it as a variety of Abies menziesii named parryana by André Michaux coming before its description by Engelmann in 1879. Despite this, Picea pungens was used as the correct name throughout this time by well known scientists such as Ludwig Beissner, Alfred Rehder, and Augustine Henry. By 1925 Picea pungens was being used for the species in US government scientific publications. It is classified in the genus Picea as part of the family Pinaceae. It has no accepted varieties, but has several in its heterotypic synonyms.

Name	Year	Rank	Notes
Abies commutata var. glauca Chargueraud	1889	variety
Abies menziesii Engelm.	1862	species	nom. illeg.
Abies menziesii var. parryana André	1876	variety
Abies parlatorei Dallim. & A.B.Jacks.	1923	species
Picea commutata Beissn.	1891	species
Picea menziesii Engelm.	1863	species	nom. illeg.
Picea menziesii var. parryana André	1876	variety
Picea parryana Sarg.	1905	species
Picea parryana argentea R.C.Rosenthal	1887
Picea parryana glauca-pendens Sudw.	1898
Picea parryana glauca-pendula André	1901
Picea pungens f. argentea Branner	1918	form	nom. illeg.
Picea pungens f. argentea Beissn.	1887	form
Picea pungens argentea-pendula Beissn.	1899		nom. subnud.
Picea pungens f. coerulea Beissn.	1891	form
Picea pungens var. compacta Rehder	1916	variety
Picea pungens f. compacta Rehder	1915	form
Picea pungens var. glauca Regel	1883	variety
Picea pungens f. glauca Beissn.	1887	form
Picea pungens glauca-pendens Sudw.	1897
Picea pungens f. glauca-pendula H.Kost. ex Beissn.	1891	form
Picea pungens var. hunnewelliana Hornibr.	1923	variety
Picea pungens f. hunnewelliana Rehder	1949	form
Picea pungens var. kosteriana A.Henry	1912	variety
Picea pungens f. kosteriana O.L.Lipa	1939	form
Picea pungens f. pendens Rehder	1949	form
Picea pungens var. pendula Zederb.	1907	variety
Picea pungens subvar. pendula Mouill.	1898	subvariety
Picea pungens f. pendula Schwer.	1920	form	nom. illeg.
Picea pungens f. perpendicularis Schwer.	1920	form
Picea pungens f. typica Schwer.	1920	form	not validly publ.
Picea pungens var. viridis Regel	1883	variety
Picea pungens f. viridis O.L.Lipa	1939	form
Pinus armata Voss	1907	species
Pinus parryana Voss	1907	species	nom. illeg.

Genetic analysis of the genus Picea indicates that the closest living relative of the blue spruce may be Picea mexicana, a disputed species from northern Mexico also known as Picea engelmannii subsp. mexicana. Together they are part of a group with seven other related species that includes all the species from North America except for Brewer's spruce. The related species include Sitka spruce, white spruce and Engelmann spruce, black spruce, red spruce, Chihuahua spruce, and Nuevo León spruce. Though visually very similar, the blue spruce and Engelmann spruce split from their common ancestor between 10 and 20 million years ago.

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 pungens means "sharply pointed", referring to the leaves.
The most frequently used common name 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. Due to its affinity with streams and well watered canyons it is also known as the water spruce. 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 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 name for this species is a compound c'ó deniní with c'ó meaning spruce and deniní meaning "it is sharp".