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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 frequently lanceolate
                   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
                     11 Leaf serrations acute; terminal shoot leaves moderately lobed
               8 Leaves and/or inflorescences hairy, at least in spring.
                       12 Terminal shoot leaves mostly ovate or rhomboid
                          13 Inflorescence densely pubescent; bracteoles thin, linear, caducous; leaves finely toothed
                          13 Inflorescence villous; bracteoles firm, persist through anthesis; leaves coarsely toothed
                       12 Terminal shoot leaves orbicular, elliptical or obovate
                            14 Terminal shoot leaves orbicular, unlobed; young leaves white-tomentose; inflorescence glabrate
                            14 Terminal leaves elliptical or obovate, prominently toothed; young leaves and inflorescence pubescent
    3 Leaves glabrous or with hairs scattered, not in tufts; [plants typically of upland habitats].
                              15 Pyrenes channeled or pitted on inner sides.
                                16 Leaves persistently pubescent, at least on petiole or main veins abaxially.
                                  17 Sepals glandular-serrate or subentire; inflorescence > 12-flowered
                                  17 Sepals often deeply glandular-serrate or glandular-pectinate; inflorescence < 10-flowered
                                    18 Leaves sharply toothed and lobed
                                    18 Leaves dentate-serrate, usually unlobed
                                16 Leaves glabrous or glabrate abaxially after maturity
                                       19 Leaves scabrate adaxially when young; stamens 7-10
                                       19 Leaves not scabrate; stamens 5-20.
                                         20 Pyrenes with a shallow groove or depression; leaf venation vaguely reticulate, barely impressed adaxially
                                         20 Pyrenes deeply grooved or pitted; leaf venation distinctly reticulate and impressed adaxially.
                                           21 Stamens 5-10 per flower; anthers 1-2 mm long
                                           21 Stamens 15-20 per flower; anthers < 1 mm long.
                                             22 Leaf blades often narrowly obovate or broadly elliptic; fruit 6-8 mm in diameter
                                             22 Leaf blades broadly obovate, rhombic or suborbicular; fruit 7-12 mm in diameter
                              15 Pyrenes plane on inner sides.
                                               23 Sepals foliaceous, equaling or exceeding petal length in flower and persistent on fruit; flowers usually 1-5 per inflorescence.
                                                 24 Terminal shoot leaves broadly elliptic or ovate, often shallowly lobed
                                                 24 Terminal shoot leaves mostly elliptic or obovate, unlobed
                                               23 Sepals not foliaceous, shorter than petals; flowers 5 or more 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.
                                                      26 Fruit black or blue; styles and pyrenes 3-5; most leaves elliptical; [native]
                                                      26 Fruit red; styles and pyrenes 2; most leaves rhombic or obovate; [exotic]
                                                    25 Thorns usually > 2 cm long; main lateral leaf veins lead only to lobe tips in lobed leaves.
                                                        27 Petioles distinctly glandular, usually with 3 or more glands persistent.
                                                          28 Stamens 5-10 (-15) per flower.
                                                            29 Fruit flesh usually hard or dense; calyx collar elevated on fruit; leaves moderately lobed on terminal shoots.
                                                              30 Anthers white or yellow
                                                              30 Anthers pink or purplish.
                                                                 31 Sepals deeply glandular-serrate; anthers pink; inflorescence glabrous
                                                                 31 Sepals finely glandular-serrate; anthers purplish; inflorescence slightly pilose
                                                            29 Fruit flesh dense or soft; calyx collar sessile or nearly so on fruit; leaves shallowly lobed or unlobed on terminal shoots.
                                                                   32 Leaves conspicuously and persistently pubescent, petiolar glands stalked.
                                                                     33 Terminal shoot leaves ovate or broadly ovate, 4-6 cm wide
                                                                   32 Leaves glabrate or sparsely pubescent, or pubescent only in spring, petiolar glands sessile.
                                                                       34 Leaf blades often obovate, fruit oblong or pyriform
                                                                       34 Leaf blades broadly elliptic or oval; fruit subglobose.
                                                                         35 Leaves usually shallowly but sharply lobed; anthers purplish; [AL, GA, SC]
                                                                         35 Leaves bluntly lobed or unlobed; anthers whitish or pink; [OK, AR, OK]
                                                          28 Stamens usually 20 per flower (often 30 or more in C. triflora).
                                                                           36 Leaves pubescent, at least abaxially; anthers white or yellowish.
                                                                              37 Sepals remotely glandular-serrate; petiolar glands sessile; fruit usually 8-12 mm diameter
                                                                              37 Sepals deeply glandular-serrate; petiolar glands stalked; fruit usually > 12 mm diameter.
                                                                                38 Leaves thin; inflorescence simple, 3-5-flowered; stamens usually 30 or more
                                                                                38 Leaves firm; inflorescence compound, > 5-flowered; stamens 20.
                                                                                  39 Terminal shoot leaves 4-5 cm wide, unlobed; sepals usually erect on fruit
                                                                                  39 Terminal shoot leaves 5-8 cm wide, with lobelike points; sepals patent in fruit
                                                                           36 Leaves glabrous; anthers pink to purplish, rarely white.
                                                                                    40 Calyx collar sessile on fruit; fruit flesh soft and succulent at maturity.
                                                                                      41 Leaves mostly unlobed; inflorescence scabrous-pubescent; petiolar glands stalked
                                                                                      41 Leaves acutely lobed; inflorescence glabrate; petiolar glands sessile
                                                                                    40 Calyx collar often elevated on fruit; fruit flesh usually dense or dry; [Pulcherrimae series].
                                                                                        42 Terminal shoot leaves shallowly lobed or unlobed, apex obtuse, margins crenate-serrate
                                                                                        42 Terminal shoot leaves shallowly to moderately lobed, apex usually acute, margins serrate.
                                                                                           43 Leaf margins often taper in a straight line from midpoint to apex
                                                                                           43 Leaf margins usually convex or bowed from midpoint to apex.
                                                                                             44 Petioles of smaller leaves winged 1/3 or less of length; leaf lobes convex-sided
                                                                                             44 Petioles of smaller leaves winged 1/2 length; leaf lobes straight on inner/distal side.
                                                                                               45 Leaf blades mostly 5-7 cm long, subcooriaceous, serrations acute
                                                                                               45 Leaf blades mostly 3-5 cm long, membranaceous, serrations obtuse.
                                                                                                 46 Anthers reddish; fruit oval, yellow; leaves glabrous
                                                                                                 46 Anthers pink; fruit subglobose, red; leaves with adaxial hairs on midvein in spring
                                                        27 Petioles eglandular, or occasionally with 1 or 2 glands deciduous or obscure after spring. xx
                                                                                                   47 Petioles often half as long as the leaf blade, or longer.
                                                                                                     48 Stamens 10 per flower; leaf blades with 4-6 pairs of main lateral veins; calyx sessile on mature fruit
                                                                                                        49 Petiole usually 15-20 mm long; fruit not pruinose
                                                                                                        49 Petiole usually 10-20 mm long; fruit usually pruinose
                                                                                                     48 Stamens 20 per flower; leaf blades with 3-4 pairs of main lateral veins; calyx collar often elevated on fruit.
                                                                                                          50 Flowers 8-10 mm wide; fruit ellipsoid
                                                                                                          50 Flowers 12-17 mm wide; fruit subglobose.
                                                                                                            51 Leaf blades 20-30 mm long, often elliptic, apex acute
                                                                                                            51 Leaf blades 30-40 mm long, usually rhombic or obovate, apex obtuse
                                                                                                   47 Petioles mostly 1/3 or less as long as the leaf blade.
                                                                                                              52 Mature leaves pubescent or villous on veins.
                                                                                                                53 Terminal shoot leaves usually ovate or rhomboid.
                                                                                                                  54 Stamens 10-15; styles 2 or 3; inflorescence slightly pubescent
                                                                                                                  54 Stamens usually 20; styles 5; inflorescence branches canescent or tomentose.
                                                                                                                     55 Terminal shoot leaves 4-6 cm long, often rhomboid
                                                                                                                     55 Terminal shoot leaves 5-9 cm long, mostly ovate or oval.
                                                                                                                       56 Fruit yellow; [TX endemic]
                                                                                                                       56 Fruit red or orange-red; [collectively widespread, but not TX]
                                                                                                                         57 Leaves flat, serrations large or coarse
                                                                                                                         57 Leaves usually cupped, serrations small, acute
                                                                                                                53 Terminal shoot leaves mostly obovate or broadly elliptical.
                                                                                                                           58 Styles and pyrenes usually 2 or 3; primary leaf veins rather obscure or not impressed; petiole winged to base.
                                                                                                                             59 Inflorescence tomentose; leaves pubescent abaxially; stamens 20
                                                                                                                             59 Inflorescence villous or glabrate; leaves usually villous; stamens 10
                                                                                                                           58 Styles and pyrenes 3-5; primary leaf veins impressed adaxially, conspicuous abaxially; petiole winged near blade.
                                                                                                                               60 Stamens 10-20; anthers white or yellowish, rarely pink; sepals glandular-serrate.
                                                                                                                                  61 Leaves usually unlobed; primary lateral veins usually 4 or 5 per side
                                                                                                                                  61 Leaves shallowly lobed; primary lateral veins 5 or 6 per side
                                                                                                                               60 Stamens 20; anthers pink; sepals subentire.
                                                                                                                                    62 Inflorescence stems glabrous; thorns > 3 cm long
                                                                                                                                    62 Inflorescence stems hairy; thorns < 3 cm long
                                                                                                              52 Mature leaves glabrous or glabrate.
                                                                                                                                      63 Primary leaf veins not impressed adaxially, somewhat obscure abaxially; petiole <10 mm long, winged to near base.
                                                                                                                                        64 Terminal shoot leaves 4.5-7 cm long; 1-3 styles and pyrenes.
                                                                                                                                          65 Terminal shoot leaves elliptic to broadly obovate
                                                                                                                                          65 Terminal shoot leaves often suborbicular
                                                                                                                                        64 Terminal shoot leaves mostly 2.5-4 cm long; 3-5 styles and pyrenes.
                                                                                                                                            66 Inflorescence pilose; stamens 20; anthers yellow
                                                                                                                                            66 Inflorescence sparsely hairy or glabrous; stamens usually 10-15; anthers usually pink
                                                                                                                                      63 Primary leaf veins impressed adaxially, conspicuous abaxially; petiole 10 mm or more, partly winged near blade.
                                                                                                                                               67 Leaf apex usually rounded; fruit 6-8 mm
                                                                                                                                               67 Leaf apex acute; fruit 10 mm or more.
                                                                                                                                                 68 Leaves with 6-9 pairs of main lateral veins; inflorescence villous or appressed-hairy.
                                                                                                                                                   69 Leaf serrations acuminate, 2-3 mm long; 2-3 styles/pyrenes; branches dark gray
                                                                                                                                                   69 Leaf serrations acute, 1-2 mm long; 3-5 styles/pyrenes; branches pale ashy-gray
                                                                                                                                                 68 Leaves with 5-7 pairs of main lateral veins; inflorescence glabrous or slightly pubescent.
                                                                                                                                                     70 Terminal shoot leaves sharply lobed; stamens usually 20
                                                                                                                                                     70 Terminal shoot leaves barely lobed or unlobed; stamens 5-15.
                                                                                                                                                       71 Leaves mostly rhomboid or suborbicular; stamens 5-10
                                                                                                                                                       71 Leaves obovate, oblanceolate or elliptical; stamens 10-15.
                                                                                                                                                         72 Sepals glandular-serrate; stamens white, yellowish or pink.
                                                                                                                                                         72 Sepals subentire; anthers pink or purplish.
                                                                                                                                                            73 Leaves often with 1-3 lobelike, asymmetrical points; styles 3 or 4
                                                                                                                                                            73 Leaves unlobed; styles usually 2