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Pinus

See list of 8 species in this genus

Reference: Kral (1993).

  • 1a. Leaves in fascicles of 5, with 1 fibrovascular bundle in cross-section; bud scales with entire margins; seed cones 8–20 cm long; umbo terminal
  • 1b. Leaves in fascicles of 2 or 3, with 2 fibrovascular bundles in cross-section; bud scales fringed on the margin; seed cones 3–10 cm long; umbo dorsal
    • 2a. Leaves in fascicles of 3; apophyses of mature seed cones red-brown (fading on older, fallen cones)
    • 2b. Leaves in fascicles of 2; apophyses of mature seed cones cream to light brown or gray, or red-brown in P. resinosa
      • 3a. Leaves (7–) 9–16 cm long, straight or only slightly twisted; seed cones symmetric, with a straight axis and without unequal development of apophyses
        • 4a. Leaves brittle, tending to break when bent; winter buds red-brown; smaller branches orange-brown; seed cones, when falling, leaving some of the basal scales on the branch (i.e., the seed cone hollow-based); umbo unarmed
        • 4b. Leaves pliable, tending not to break when bent; winter buds gray; smaller branches brown to gray-brown; seed cones falling with all the scales intact; umbo armed with a slender prickle (though the prickle often deciduous)
          • 5a. Winter buds resinous; growth habit relatively uniform and often with an unbranched main stem; seed cones sessile, with a ± rounded base
          • 5b. Winter buds not resinous; growth habit irregular, the main stem and branches often forked; seed cones stalked, with a ± truncate base
      • 3b. Leaves 2–7 (–8) cm long, noticeably twisted (relatively straight in the planted P. mugo); seed cones ± asymmetric, with a curved axis and/or obviously unequal development of apophyses on one side

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