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Key to Crataegus, Key C: hawthorns with leaf blades widest at midpoint or beyond midpoint; blade bases acute or cuneate;
leaves eglandular, or if glandular then twigs and branchlets not geniculate

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1 Leaves abaxially canescent, margins mostly entire; fruit calyx open, exposing pyrenes
1 Leaves abaxially pubescent, villous or glabrous, margins toothed; fruit calyx not fully open.
  2 Leaves spatulate or oblanceolate, < 13 mm wide; fruit < 6 mm diameter; pyrenes about 3 mm long
  2 Leaves variously shaped but most > 13 mm wide; fruit > 6 mm; pyrenes 4 mm long or more.
    3 Leaves abaxially with dense hair tufts in proximal main vein axils, especially in spring; [plants typically of wet or floodplain habitats].
      4 Inflorescence simple, 1-5-flowered; fruit 10-15 mm diameter, lustrous red, mature in late spring.
        5 Leaf blades mostly 5-7 cm long, elliptic, margin wavy or with uneven, blunt teeth
        5 Leaf blades usually < 5 cm long, most obovate, margin finely toothed.
          6 Leaf adaxial surface usually glossy; whitish hair tufts in main vein axils abaxially
          6 Leaf adaxial surface matte; reddish hair tufts in main vein axils abaxially
      4 Inflorescence compound, 5-20-flowered; fruit 5-15 mm diameter, dull red or orange-red, mature in autumn.
             7 Petiole 5-10 mm long; terminal shoot leaves < 25 mm broad
             7 Petiole > 10 mm long; terminal shoot leaves > 25 mm broad; [Virides series and hybrids].
               8 Leaves glabrous, except for hair tufts.
                 9 Leaves mostly ovate; terminal shoot leaves suborbicular, unlobed or barely lobed; bases rounded
                 9 Leaves predominately lanceolate, elliptical, rhomboid or obovate; terminal shoot leaves often ovate; bases usually cuneate.
                   10 Leaves rarely lanceolate, mostly elliptical or rhomboid.
                     11 Leaf serrations small or crenate; terminal shoot leaves often incised on each side nearly to midrib
               8 Leaves and/or inflorescences hairy, at least in spring.
    3 Leaves glabrous or with hairs scattered, not in tufts; [plants typically of upland habitats].
                                16 Leaves persistently pubescent, at least on petiole or main veins abaxially.
                                               23 Sepals foliaceous, equaling or exceeding petal length in flower and persistent on fruit; flowers usually 1-5 per inflorescence.
                                                    25 Thorns short (< 2 cm), or spinose spur shoots present; main lateral leaf veins run to sinuses and lobe tips in lobed leaves.
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