Pinus edulis, the pinyon pine, Colorado pinyon, or simply pinyon (US: /ˈpɪnjən/ PIN-yuhn, UK: /piːˈnjɒn/ pee-NYON, or /pinˈjɑn/ peen-YAHN), is a species of pinyon pine from the southwestern United States noted for its large, edible seeds. Although all of the species in its section of the pine genus are called pinyon pines this is the species most associated with the name.
Description The pinyon pine is a shrub to moderate sized tree growing to as much as 21 meters (69 ft) in height, but is more typically 5 to 15 meters (16–49 ft) tall. When young the crown of the tree is fairly pyramid shaped, but becomes more rounded with age. Young trees also have branches nearly at ground level and only losing them once the tree is quite mature. With increasing age the crown can become more open and irregular with a gnarled appearance. The crown is usually nearly as broad as the tree's height. A pinyon pine with a trunk diameter of 1.72 meters (5 ft 8 in) has been documented, though a thickness of 60 cm (2 ft) at breast height is more typical of fully mature trees. The bark is sepia-brown thin, and scaly when new, eventually becoming unevenly furrowed and gray. The twigs are lite red-brown to tan that fade to gray and are usually rough with small warty nodules, but can occasionally be smooth. The needle-like leaves are usually two to a bundle, but might also be three to a bundle or solo, but the sheath at the base of the bundle is lost early. They curve upwards and are 2–4 centimeters (0.8–1.6 in) long and just 0.9–1.5 millimeters wide. Solitary needles have two groves while those in two-needle bundles have two sides. When three are three needles to a bundle they will have three sides. They are blue-green with pale bands of stoma, especially on the upper surface, and can either have smooth edges or very fine serrations. The classic two leaved Colorado pinyon needle will have a crescent shaped cross section with two or three resin ducts. Each needle lasts four to six years. Pinyon pine buds are red-brown, resinous, ellipsoid to egg-shaped, and 0.5–1 cm long. Buds a formed in the summer and begin developing into new twigs and needles the following spring. The pollen cones are typically 3–6 mm long; yellowish to red-brown and ellipsoidal. New seed cones in the spring are small, around 6.4 mm (0.25 in) in diameter and resemble a pincushion pale yellow-green to red-purple in color. When receptive the seed cone's scales open to accept pollen blown breezes from other trees. By fall it will have reached about 1.3 cm (0.5 in). In the second year the green seed cone will developing to full maturity, growing through the spring and summer. When mature the seed cones can be 3 to 5 centimeters (1.2–2.0 in), but are typically around 4 cm.
The seeds are somewhat egg-shaped ellipsoids to fully ellipsoid, and large for a pine, mostly measuring 8–16 millimeters long with thick brown shells. Cones can also contain seeds with light tan shells, but these are almost invariably hollow and sterile. They are wingless and leave quite visible hollows in the cone scales. Pinyons bear cone seeds at a fairly young age, just 25 years old when they are 1.5 to 3 meters (5–10 ft) tall, though they do not produce large quantities of seeds until 75 to 100 years of age. As a long lived tree they can produce large crops for centuries. Areas with stable woodlands, undisturbed by fire, have living trees from 300 to 1,000 years old. Pinyon pines are very similar to the single-leaf pinyon (Pinus monophylla), but most of the needles on the single-leaf pinyon are solitary and round in cross section, though often with a grove on each side. The solitary needles also give the twigs of the single-leaf pinyon a more spiky look; its crushed needles are described as smelling 'pungent' while those of the pinyon pine are 'fragrant'. However, there is a population of trees in central Arizona south of the Mogollon Rim that will often grow single needles in dry years and two needles in wet years, that may or may not be part of the species. This pattern is repeated in at least one population of trees in Nevada.
Phytochemistry The oleoresin, the gummy crude turpentine produced by wounds, from the pinyon pine is largely α-pinene, δ-3-carene, and ethyl octanoate. The large amounts of ethyl octanoate, more than 20 times as much compared with single-leaf pinyon pines, is responsible for the characteristic pleasant odor of the trees. The essential oils from the trunk of the tree are similar, being largely α-pinene, ethyl octanoate, germacrene D, with some trees also containing significant amounts of longifolene. Needles essential oils are more than half α-pinene, with variable amounts of longifolene and significant amounts of β-pinene, myrcene, 6-3-carene, beta phellandrene, ethyl octanoate, and bornyl acetate.
Taxonomy
Pinus edulis was scientifically described and named by the botanist George Engelmann in 1848. He described the species from specimens sent to him by Friedrich Adolph Wislizenus from the Sangre de Cristo Range in New Mexico. It is part of subsection Cembroides within the genus Pinus, which is classified in the Pinaceae family. It has been described as a subspecies or variety of Pinus cembroides.
Pinus edulis forms natural hybrids with other species, including Pinus cembroides and Pinus monophylla. A named nothospecies called Pinus × kohae Frankis is listed as accepted in Plants of the World Online, but is formed with a disputed species named Pinus californiarum. They are a population of single leaved pines largely south of the Mogollon Rim in Arizona and the transition between the two groups have also been interpreted as being a variety named P. edulis var. fallax.
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