Adaptation: Dry mountain slopes, mesas, plateaus, growing scattered in open woodlands at 1200-2450 (-2700) meters elevation, in pure stands, or commonly mixed with one or more of several species of juniper. Two-needle pinyon is one of the most slow-growing and drought-resistant species of pines, requiring only 12-18 inches of rainfall a year, but it grows best on the higher, wetter sites, just below the zone of ponderosa pine.
Planting: Trees may begin producing cones when 25 years of age but produce significant quantities of seed only after reaching 75-100 years old. Good seed crops occur every 4 to 7 years (on average) or more frequently on better sites, and cone bearing tends to be synchronous over large geographical areas. Germination is generally above 80%.
A relationship of mutual benefit exists between two-needle pinyon and four species of corvid birds: Clark’s nutcracker, Steller’s jay, scrub jay, and pinyon jay. These birds are the primary agents of dispersal of this pine, which provides a large portion of their diet and subsistence, but only the scrub jay and pinyon jay cache seeds in the pinyon-juniper zone and are responsible for its regeneration.
Seed germination and establishment of the two-needle pinyon are best in the shade of trees or shrubs and probably depend on an adequate moisture supply during the first summer. Growth through all stages is extremely slow. Dominant trees in a stand are often 400 years old, and individuals 800-1000 years old have been found.
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