Contains 10 accepted taxa overall.

Characteristics
Crataegus L.
HAWTHORN
A recent FNA treatment recognized 169 species in the USA and Canada and 42 species (one as a hybrid) in Florida. This treatment mostly follows Ward (2009).
Classification
ROSALES
Crataegus
Citation
CRATAEGUS Linnaeus, Sp. Pl. 475. 1753, nom. cons. vs. Mespilus Linnaeus 1753.
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TYPE: Crataegus oxyacantha Linnaeus, nom. rej. Lectotypified by Britton & A. Brown, Ill. Fl. N. U.S., ed. 2. 2: 294. 1913; M. L. Green, Prop. Brit. Bot. 158. 1929.
Species
Scientific Name Common Name Herbarium Specimens Status Photos
Crataegus aestivalis MAY HAW; MAY HAWTHORN Native OBL (NWPL) OBL (DEP)
Crataegus crus-galli COCKSPUR HAWTHORN Native FAC (NWPL)
Crataegus flava YELLOWLEAF HAWTHORN; BEAUTIFUL HAWTHORN; SARGENT'S HAWTHORN Native FAC (NWPL)
Crataegus marshallii PARSLEY HAWTHORN Native FAC (NWPL) FACW (DEP)
Crataegus michauxii MICHAUX'S HAWTHORN Native
Crataegus opaca RIVERFLAT HAWTHORN; WESTERN MAYHAW Native OBL (NWPL)
Crataegus phaenopyrum WASHINGTON HAWTHORN Native Endangered-State FAC (NWPL)
Crataegus spathulata LITTLEHIP HAWTHORN Native FAC (NWPL)
Crataegus uniflora DWARF HAWTHORN Native
Crataegus viridis GREEN HAWTHORN Native FACW (NWPL) FACW (DEP)
[Family identification key]
1.  Proximal vein axils of leaf blade undersides cavernous, forming pubescent (rarely glabrate) pockets (domatia)
2
1.  Proximal vein axils of leaf blades undersides flush with the rest of the blade, glabrous (midrib and secondary veins sometimes sparsely pilose)
8
2.  Leaf blades mostly dentate to serrate, the teeth generally triangular, the blades mostly (3)4-7 cm long
3
2.  Leaf blades mostly subentire to crenate, the teeth generally rounded, the blades mostly 1-5 cm long
5
3.  Leaf blade underside glabrescent except for pubescence around domatia; pedicels 5-15 mm long; fruits 5-8 mm wide
3.  Leaf blade underside midribs and veins densely rufous-pubescent; pedicels 0-3 mm long; fruits (8)12-15 mm wide
4
4.  Leaf blade elliptic to broadly elliptic, lateral veins 5-9 per side; pedicels glabrate; fruits 12-15 mm wide
4.  Leaf blade broadly elliptic to obovate; lateral veins 3-5 per side; pedicels rufous-pubescent; fruits 10-12 mm wide
5.  Leaf blade upperside glabrous to scabridulous, underside midribs and veins sparsely strigose, sparsely pubescent, to glabrous except for pale pubescence around domatia; leaf blade and bracteole marginal glands obscure; fruits 8-20 mm wide; of hydric to mesic-hydric areas
5.  Leaf blade upperside and underside sparsely strigose to denseely pubescent; fruits (5)6-12(15) mm wide; of xeric to mesic-xeric areas
6
6.  Leaf blade margins without glands or these obscure
6.  Leaf blade and bracteole marginal glands usually prominent
7
7.  Branches weeping or pendent; leaf blade narrowly spatulate (sometimes broader on young shoots)
7.  Brnaches spreading, not pendent; leaf blade broadly spatulate to obovate
8.  Leaf blades broadest near the base
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8.  Leaf blades broadest above the middle
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9.  Leaf blades pinnately dissected-lobed, sinuses nearly reaching midrib
9.  Leaf blades shallowly lobed, sinus less than halfway to midrib
10
10.  Leaf blades with 2 lateral lobes, the lobe tips acuminate; ovary 4-5 mm wide, fruits 8-10 mm wide
10.  Leaf blades weakly lobed, the lobe tips acute; ovary 2-3 mm wide, fruits 4-5 mm wide
11.  Pedicels 1-3 mm long; sepals often coarsely dentate with teeth >0.5 mm long
11.  Pedicels (4)8-25 mm long; sepals entire to weakly dentate with teeth <0.5 mm long
12
12.  Pedicel pubescent; sepals narrowly acute, 3-4 mm long; fruit >4 mm wide
12.  Pedicel glabrous; sepals deltoid, 1-2 mm long; fruit 3-4 mm wide
Genus Synonyms
Synonym Full Citation Basionym Type
Anthomeles Anthomeles M. Roemer, Fam. Nat. Syn. Monogr. 3: 102, 140. 1847. TYPE: Non designatus.
Azarolus Azarolus Borkhausen, Theoret. Handb. Forstbot. 2: 1224. 1803. TYPE: Non designatus.
Halmia Halmia Medikus ex M. Roemer, Fam. Nat. Syn. Monogr. 3: 101, 134. 1847. TYPE: Non designatus.
Oxyacantha Oxyacantha Medikus, Philos. Bot. 1: 150, 154, 155. 1789. TYPE: Non designatus.
Phaenopyrum Phaenopyrum M. Roemer, Fam. Nat. Syn. Monogr. 3: 103, 152. 1847. TYPE: Non designatus.
Phalacros Phalacros Wenzig, Linnaea 38: 164. 1874. TYPE: Phalacros cordata (Miller) Wenzig (Mespilus cordata Miller)
Xeromalon Xeromalon Rafinesque, New Fl. 3: 11. 1838. TYPE: Xeromalon obovatum Rafinesque