1 Leaves either borne in fascicles of 2-5 (basally bound by a scarious sheath) or on short shoots in clusters of many leaves in apparent whorls.

  2 Leaves borne in fascicles of 2-5 (basally bound by a scarious sheath); [subfamily Pinoideae]

  2 Leaves borne on short shoots in clusters of many (>10) leaves in apparent whorls.

    3 Leaves evergreen; cones 6-12 cm long; [subfamily Abietoideae]

    3 Leaves deciduous; cones 1-2 cm long; [subfamily Pinoideae]

1 Leaves alternate.

      4 Leaves distinctly flattened (2-sided) in cross-section.

        5 Leaves jointed, on short, persistent base; cones 1-3.8 cm long, pendent; [subfamily Abietoideae]

        5 Leaves attached directly to twig; cones 4-15 cm long, erect (Abies) or pendent (Pseudotsuga)

          6 Seed cones erect, disintegrating scale by scale and leaving the cone axis as a persistent spike on the tree; [subfamily Abietoideae]

          6 Seed cones pendent, falling whole from the tree; [subfamily Pinoideae]

1 Leaves opposite or in whorls of 3.

  2 Longest internodes 2-10 cm long; stems green, Equisetum-like

  2 Longest internodes < 1 cm long; stems green, brown, or tan, not resembling Equisetum.

    3 Leaves scale-like or acicular and <16 mm long; mature cones either dry and cone-like, or fleshy and < 12 mm in diameter

    3 Leaves linear, 15-45 mm long; mature female “cones” fleshy and drupe-like, > 15 mm in diameter

      4 Leaf apex acute, but not stiff, pungent, or spinose; midvein obviously raised (use 10× magnification) on the upper surface, that surface flat or nearly so, except for the revolute margins; stomatal bands on the leaf undersurface broad, white, together making up about 3/4 of the width of the leaf; drupe-like 'fruit' 18-25 mm long, brown, brown or brownish-orange and not striped

      4 Leaf apex acuminate, extended into a stiff, pungent spine; midvein not obviously raised on the upper leaf surface, that surface convex-curved; stomatal bands on the leaf undersurface narrow, greenish gray, together making up about 1/4 of the width of the leaf; drupe-like 'fruit' 25-35 mm long, dark-green and also longitudinally striped with paler green, tan, or purple

1 Leaves either alternate, or in fascicles of 2-5 (basally bound by a scarious sheath), or on short shoots in clusters of many 10-60 leaves in apparent whorls.

        5 Leaves either borne in fascicles of 2-5 (basally bound by a scarious sheath) (Pinus) or on short shoots in clusters of many leaves in apparent whorls (Cedrus, Larix)

        5 Leaves alternate.

          6 Leaves 4-angled in cross-section.

             7 Twigs green

          6 Leaves distinctly flattened (2-sided) in cross-section.

               8 Leaves (fresh) very soft in texture, seasonally deciduous as twiglets; [primarily Coastal Plain]

               8 Leaves (fresh) stiffer in texture, evergreen; [collectively more widespread].

                 9 Leaves tapering from base to a long-acuminate tip

                 9 Leaves with parallel margins for most of their length, or widest near middle and gradually tapering to base and apex, the apex acute, obtuse, or retuse.

                   10 Cone dry, brown, and woody at maturity

                   10 ”Cone” fleshy, red or purplish at maturity

                     11 Seed surrounded by a fleshy scale, appearing drupe-like, this also subtended by a swollen and fleshy receptacle

                     11 Seed partially or fully enclosed in a fleshy aril, the subtending receptacle neither swollen nor fleshy

                       12 Leaf apex acuminate, extended into a stiff, pungent spine; midvein not obviously raised on the upper leaf surface, that surface convex-curved; stomatal bands on the leaf undersurface narrow, greenish gray, together making up about 1/4 of the width of the leaf; drupe-like 'fruit' 25-35 mm long, dark-green and also longitudinally striped with paler green, tan, or purple, the leathery exterior fully enclosing the seed

                       12 Leaf apex acute, but not stiff, pungent, or spinose; midvein obviously raised (use 10× magnification) on the upper surface, that surface flat or nearly so, except for the revolute margins; stomatal bands on the leaf undersurface medium to broad, white or whitish-green, together making up about 1/2 or 3/4 of the width of the leaf; drupe-like 'fruit' either 4-7 mm long, red or orange when ripe, with a softly fleshy exterior open at the top (the seed) visible, or 18-25 mm long, brown, brown or brownish-orange and not striped, the fleshy exterior fully enclosing the seed.

                          13 Stomatal bands on the leaf undersurface broad, white, together making up about 3/4 of the width of the leaf; drupe-like 'fruit' 18-25 mm long, brown, brown or brownish-orange and not striped, the fleshy exterior fully enclosing the seed; leaf resin canal present, below the vascular tissue (break leaf and use 10× magnification); drupe-like 'fruits' clustered on peduncles

                          13 Stomatal bands on the leaf undersurface medium, whitish-green, together making up about 1/2 of the width of the leaf; drupe-like 'fruit' 4-7 mm long, red or orange when ripe, with a softly fleshy exterior open at the top (the seed) visible; leaf resin canal absent; drupe-like 'fruits' solitary, sessile or nearly so