Flora of the Southeastern United States
2022 Edition


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Key to Juniperus

1 Leaves flat-acicular or grooved, 8-25 mm long, never scale-like, with a white stomatal band on the upper surface; leaves borne in whorls of 3, spreading at 45-90 degrees from the twig; female cones ("berries") axillary, maturing in 2-3 years; [section Juniperus]
..2 Leaves U- or V-shaped in ×-section; white stomatal band <1× as wide as the green leaf margin; female cone (“berry”) 8-12 mm in diameter; procumbent shrub
..2 Leaves flat to broadly curved in ×-section; white stomatal band 1-3× as wide as the green leaf margin; female cone (“berry”) 6-10 mm in diameter; prostrate to spreading-ascending shrub or columnar small tree.
....3 White stomatal band 2-3× as wide as the green leaf margin; strict, columnar trees; leaves 15-20 (-30) mm long, straight (not curved)
....3 White stomatal band 1-1.5× as wide as the green leaf margin; prostrate or low shrub with ascending branchlet tips (or occasionally a spreading shrub or small strict tree to 2-4 m tall; leaves 10-15 mm long, linear and spreading or curved upwards
1 Leaves primarily scale-like (scale-leaves), ca. 1-2 mm long, though acicular and 2-10 mm long (whip-leaves) are often present on young trees and some lower branches of larger trees, without a white line on the upper surface (though often somewhat glaucous); leaves of mature twigs borne in opposite pairs of 2, decussate (thus 4-ranked), appressed to the twig (leaves of immature twigs sometimes in whorls of 3, spreading at 10-45 degrees from the twig); female cones ("berries") terminal on short branches, maturing the first year; [section Sabina].
......4 Margins of scale-leaves entire; [collectively widespread in our area].
........5 Prostrate shrubs, < 3 dm tall; apex of scale leaves apiculate; female cones ("berries") with 3-5 seeds; (Long Island NY and northwards]
........5 Upright shrubs or trees; apex of scale leaves obtuse to acute; female cones ("berries") with 1-2 (-3) seeds; [collectively widespread].
..........6 Female cones ("berries") 3-4 mm long; male cones 4-5 mm long; terminal twigs 0.75-0.90 mm wide (including the scale-like leaves); scale leaves 1.20-1.45 mm long, obtuse to acute; trees generally with rounded or flattened crowns, the lower branches often drooping; [upland to wetland saline or calcareous habitats near the coast]
..........6 Female cones ("berries") 4-7 mm long; male cones 3-4 mm long; terminal twigs 0.85-1.00 mm wide (including the scale-like leaves); scale leaves 1.40-1.65 mm long, acute; trees generally with sharply tapered crowns, the lower branches generally ascending; [upland habitats inland]
......4 Margins of scale-leaves finely and irregularly toothed (use at least 10× and preferably 20× magnification); [s. MO, AR, and e. TX westwards and southwestwards].
............ 7 Scale-leaves lacking a raised hemispheric gland; mature female cones ("berries") copper to reddish-brown and lacking a glaucous 'bloom'
............ 7 Scale-leaves with a raised hemispheric gland; mature female cones ("berries") dark blue and with a glaucous 'bloom'.
............ ..8 Whip-leaf glands hemispherical; female cones ("berries") (8-) avg. 9 (-10) mm in diameter; seeds usually 1 per cone
............ ..8 Whip-leaf glands oval to elliptical; female cones ("berries") (5-) avg. 6 (-8) mm in diameter; seeds usually 2 per cone