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Quercus
See list of 16 species in this genusThe following identification key has been written for mature sun leaves. Due to the differences in shape and pubescence between sun and shade leaves, adjustments may be needed if shade leaves are used. References: Palmer (1948), Miller and Lamb (1985), Jensen (1997), Nixon and Muller (1997).
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1a. Leaf blades with bristle-tipped teeth or lobes (entire in Q. imbricaria and Q. phellos,
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2a. Leaf blades entire
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3a. Leaf blade ovate to elliptic or obovate, 15–75 mm wide; petioles 10–20 mm long; carpellate involucres 5–9 mm tall and 10–18 mm in diameter; nuts 10–18 mm wide
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3b. Leaf blade linear to narrow-elliptic, 10–25 mm wide; petioles 2–4 (–6) mm long; carpellate involucres 3–6.5 mm tall and 7.5–11 mm in diameter; nuts 6.5–10 mm wide
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2b. Leaf blades lobed
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4a. Petioles (8–) 10–25 mm long; nut 8–11 mm wide, the outer surface pubescent; leaf blades abaxially tomentose, with triangular to ovate lobes; short to tall shrubs up to 5 m tall
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4b. Petioles 20–70 mm long; nut 9–21 mm wide, the outer surface glabrous or nearly so; leaf blades abaxially glabrous or with hairs along the veins and/or in the axils of veins (infrequently with patches of tomentum on the surface in Q. velutina), with oblong or rectangular lobes; trees to 30 m tall
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5a. Carpellate involucre pubescent on the inner surface, the marginal bracts loose and projecting, forming a fringe around the nut; terminal winter buds 7–10 mm long, the scales pubescent on the abaxial surface [Fig. 663]
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5b. Carpellate involucre glabrous on the inner surface or with a ring of hairs around the nut scar, the marginal bracts covered and concealed, not forming a fringe; terminal winter buds 3–7 mm long, the scales glabrous on the abaxial surface or pubescent only near the apex
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6a. Terminal winter bud pubescent in the apical half, noticeably 5-angled in cross-section; carpellate involucre concealing ⅓ to ½ of the nut; nut with 1 or more concentric rings of fine pits near the apex [Fig. 659]
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6b. Terminal winter bud glabrous or with a few hairs near the apex, terete to obscurely angled in cross-section; carpellate involucre concealing ⅕ to ⅓ of the nut; nut lacking rings of fine pits near apex
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7a. Sinuses of leaf blade generally extending more than ½ the distance from the tips of the lobes to the midrib; nut 10–16 mm long; carpellate involucre 9.5–16 mm in diameter; terminal winter buds bluntly pointed at apex, 3–5 mm long
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7b. Sinuses of leaf blade generally extending less than ½ the distance from the tips of the lobes to the midrib; nut 15–30 mm long; carpellate involucre 18–30 mm in diameter; terminal winter buds sharply pointed at apex, 4–7 mm long
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1b. Leaf blades with rounded to acutely pointed teeth or lobes (the teeth with an apical papilla in Q. muehlenbergii and Q. prinoides) [Fig. 660]; bracts of carpellate involucre thickened and/or with darkened or pubescent calluses at the base; fruits maturing in first year, therefore, only 1 size of fruit present on a given plant; inner surface of endocarp glabrate or minutely pubescent near base and apex
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8a. Terminal and axillary winter buds with persistent, filiform stipules; carpellate involucre with irregularly spreading scales
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8b. Winter buds without persistent stipules; carpellate involucre with closely appressed scales
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9a. Leaf blades with prominent lobes, at least some of the sinuses extending more than ⅓ the distance from the tip of the lobes to the midrib; mature leaf blades abaxially glabrous or pubescent
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10a. Mature leaf blades abaxially glabrous or essentially so (at least appearing so without high magnification); branchlets glabrous
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11a. Leaf blades cuneate at the base, on petioles 8–25 mm long; nut subsessile or on a peduncle to 25 (–40) mm long; carpellate involucre concealing ¼ (rarely to ⅓) of the nut
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11b. Leaf blades cordate at the base, on petioles 4–8 mm long; nut on a peduncle (25–) 35–65 (–100) mm long; carpellate involucre concealing ⅓ to ½ (or more) of the nut
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10b. Mature leaf blades abaxially with simple and/or stellate hairs; branchlets often pubescent
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12a. Leaf blades typically with 1 or more deep sinuses near or below the middle of the blade that extend more than ½ distance from the tips of the lobes to the midrib, the distal portion of the blade with shallower sinuses or merely with tooth-like lobes [Fig. 660]; carpellate involucre (8–) 15–50 mm tall, the scales terminated by soft awns, these forming a loose, marginal fringe; branches often with corky wings
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12b. Leaf blades usually either ± regularly lobed or with deeper sinuses toward the apex, in either case lacking a pandurate shape; carpellate involucre 7–15 (–18) mm tall, the scales not projecting to form a fringe; branches lacking corky wings
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13a. Leaf blades often cruciform (i.e., with 2 larger lobes that project at ± right angles from the midrib), abaxially with minute, stellate hairs; peduncle up to 6 (–40) mm long
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13b. Leaf blades variably lobed, but never cruciform, abaxially with both minute, stellate hairs and taller, erect, 1- to 4-rayed hairs; peduncles (20–) 40–70 mm long (in part)
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9b. Leaf blades with short, tooth-like lobes, the sinuses extending less than ⅓ the distance from the tip of the lobes to the midrib; mature leaf blades abaxially with simple and/or stellate-branched hairs
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14a. Peduncle (20–) 40–70 mm long; leaf blades abaxially with both minute, stellate hairs and taller, erect, 1- to 4-rayed hairs across the surface; plants of swamps, riparian forests, and other poorly drained habitats (in part)
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14b. Peduncle essentially absent or up to 20 (–25) mm long; leaf blades abaxially with only minute, stellate hairs across the surface, though taller, erect hairs are found along the veins in Q. montana (taller, erect, red hairs often found across the abaxial surface in coastal MA populations of Q. prinoides); plants of dry, well-drained ridges, slopes, and plains
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15a. Leaf blade abaxially with both minute, stellate hairs and taller, erect simple or fascicled hairs along the veins, each tooth-like lobe lacking a papilla-like point; bark dark gray to dark brown with deep furrows, neither flaky nor scaly; carpellate involucre 18–25 mm in diameter; peduncle 8–20 (–25) mm long
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15b. Leaf blades abaxially with sparse to dense, minute stellate hairs only (coastal MA populations of Q. prinoides often have erect, reddish hairs in addition the stellate ones), each tooth-like lobe terminating with a papilla-like point [Fig. 661]; bark gray, without deep furrows, flaky or scaly on mature stems; carpellate involucre 8–20 (–22) mm in diameter; peduncle up to 8 mm long
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16a. Leaf blades with (9–) 10–14 (–16) pairs of secondary veins; small trees to 18 m tall, usually found on limestone and marble hills and outcrops
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16b. Leaf blades with 5–8 (–9) pairs of secondary veins [Fig. 661]; colonial shrubs rarely exceeding 3 m in height, found usually on dry soils of ridges and sandy plains
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Each photo represents one species in this genus.