|Pinus aristata (Engelmann)
by Kirsten Aamodt, Native Plants Class 2003
Common names: Bristlecone pine, foxtail pine, hickory pine.
Synonymy: Pinus balfouriana Greville & Balfour var. aristata (Engelmann) Engelmann Etymology: Pinus is Latin for pine. The specific epithet can be translated into awned, probably referring to the incurved prickles extending from the tips of the cone scales. (1).
Growth form: Pinus aristata is a tree achieving heights of 15 m. The appearance is very bushy with a rounded crown, and dense with foliage often stemming from ground level. Notable are the disfigured, twisted, and sheared semblances these pines can acquire while demonstrating their ability to continue to slowly grow in spite of the soil erosion; drought; wind, sand and ice blasting occurring in their timberline habitats (3, 4, 8).
Roots: In saplings the roots are sparse and successful transplants become increasingly less successful with age and increased size.
Stem: Commonly malformed and up to a meter in diameter. Young trunks will have smooth, pale gray and thin bark. On mature trees it is reddish brown, scaly, shallowly furrowed, with flattened irregular ridges. The wood is densely resinous. Branches can be contorted and sheared to the leeward side with pale red-brown bark ageing to gray. Twigs are stout, covered with soft hairs, orange turning black, clothed in thick tufts of foliage resembling bottlebrushes. (4, 6, 8)
Leaves: Crowded together, the long persistent needles (10 –17 years (4, 6) are stout, upcurved, and 2.5-4 cm long by .08-1 mm wide. Occurring in fascicles of 5, needles are deep blue-green, lustrous, with drops or scales of white resin dotting their inside surface. There is an obvious, narrow, median groove along the outside surface (4, 6, 8).
Pollen Cones: The male cones are ellipsoid, 10 mm long and bluish to dark orange-red (4, 6, 8).
Seed Cones: The purple to brown seed cones are nearly sessile, 6-11 cm in length, mature in 2 years, and shed their seeds before falling. The cone scales have a thickened triangular base extending into a fragile incurved bristle 4-10 mm long. Seeds are 5-6 mm with a 10-13 mm long grayish to black wing (3, 4, 5, 6).
Similar species: Populations of Pinus longaeva have been separated from Pinus aristata by the Colorado Green River drainage, a distance of 260 km, for millions of years. They differ from each other in needle structure and cone morphology (5). Both are known as Bristlecone pines, live in high alpine environments and are famous for their longevity. Methuselah is the name given to a specimen of P. longaeva that is considered the oldest living tree in the world. Ages given vary from 4000 to 5000 years. Ages given for specimens of P. aristata vary from 1500 to 2500 years. The two are definitively distinguished by distribution. In Arizona, P. aristata grows in conjunction with Pinus flexilis, which also has needles in bundles of 5. However, the foliage of P. flexilis is bunched at branch ends rather than clothing the entire branch and the cones are larger, and lack the bristle (5, 8).
Life history: Perennial. Evergreen. Tree.
Native/introduced: Native, occurring in pure, same aged stands or in associations with Pinus flexilis, Abies concolor, Abies lasiocarpa, Picea engelmannii, Pinus ponderosa, and/or Populus tremuloides in montane and subalpine areas at elevations of 2300-3650 m (3, 8).
Photosynthetic pathway: C3
Phenology: Undaunted by the short growing season and daily temperature extremes, P. aristata buds in June, shoots grow in July, and active growth can occur from June to September. Pollen cones bud in July and pollen falls in late July. Seed cones mature in July and open in late September shedding seeds through October. Leaves are shed in October (3).
Distribution: CO, NM, and AZ (2, 5, 8). Also in CA, NV and on the eastern slopes of the Laramie Range in southwest WY, south through the San Juan Mountains of CO, to the Sangre de Cristo Mountains of NM, with a disjunctive population occurring in northern AZ’s San Francisco Peaks in Coconino County (3, 9).
The soft, resinous wood has little lumber value, is locally used as fuel or props in mines, salvage protected in Arizona (3, 4). Cover is provided and seeds are edible by Clark’s Nutcracker, various other small birds and small mammals. Popular as a Bonsai specimen. Due to its longevity, its greatest significance to modern man is as a cross reference for radiocarbon dating and the tree ring chronologies for paleoclimatic indicators, especially for temperature fluctuations. Fires are not problematic in bristlecone habitats as severe weather factors inhibit understory growth, and with needles shedding only every 10 –17 years, little litter exists as fuel (3). Shoshoni Indians used a poultice of heated pitch to apply to sores and boils (10).
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