1. Inflorescences 2–6-flowered (± umbellate); flowering before or with young leaves, anthesis very early, before other sympatric hawthorns; pomes ripe May–late June; se United States, wetlands. | C. ser. Aestivales |
1. Inflorescences usually 7–25-flowered (if 1–6-flowered, not ± umbellate); not flowering before or with young leaves, anthesis later; pomes ripe August–October; mostly in toplands, except few se United States species | → 2 |
2. Bracteoles, at least larger, usually ± herbaceous, usually ± persistent, others sometimes membranous but sometimes caducous; flowers 18–30 mm diam | → 3 |
2. Bracteoles usually ± membranous, sometimes ± herbaceous, usually caducous, sometimes fugacious or ± persistent, rarely deciduous; flowers 8–25(–26) mm diam | → 8 |
3. Leaves and petioles eglandular or sparsely glandular | → 4 |
3. Leaves and petioles gland-dotted or stipitate-glandular | → 5 |
4. Pomes orange-red, bright or deep red, or bright yellow, not pruinose; flesh mealy; fruiting sepals erect or erect-patent to broadly spreading, rarely incurved, often ± accrescent; larger bracteoles narrowly oblong, abaxially villous. | C. ser. Molles |
4. Pomes bright pink to crimson, glabrous or pubescent at ends; flesh ± hard; fruiting sepals spreading or ± reflexed, non-accrescent; larger bracteoles oblong to curved, abaxially glabrous. | C. ser. Dilatatae |
5. Flowers 25–30 mm diam.; stamens 10 or 30–45(–47); shrubs multi-stemmed, main trunk not dominant; leaf blades ± chartaceous; inflorescences frequently arising laterally from extension shoots. | C. ser. Triflorae |
5. Flowers 18–25 mm diam.; stamens (5 or)10 or 20–25; shrubs or trees 1- to few-stemmed, main trunk dominant; leaf blades usually thick and ± chartaceous or thinner but subcoriaceous; inflorescences either arising solely subterminally from woody short shoots (ser. Molles, ser. Dilatatae), or sometimes arising laterally from extension shoots (ser. Bracteatae) | → 6 |
6. Leaves: lobes 0 or 1–4 per side, merely apiculi or sinuses very shallow, deep green, subcoriaceous; petioles 15–25% length of blade; inflorescences 3–12-flowered; stamens 20(–25); larger bracteoles ligulate, semipersistent, margins strongly stipitate-glandular. | C. ser. Bracteatae |
6. Leaves: lobes usually 1–6 per side, distinct, sinuses shallow to deep, green or bluish green, ± thick or chartaceous; petioles 30–50% length of blade; inflorescences 5–20-flowered; stamens (5 or)10 or 20; larger bracteoles narrow to linear, subherbaceous, margins sessile-glandular (ser. Molles), or larger bracteoles oblong to curved, abaxially glabrous, margins strongly stipitate-glandular (ser. Dilatatae) | → 7 |
7. Pomes orange-red, bright or deep red, not pruinose; flesh mealy; fruiting sepals erect or erect-patent to broadly spreading, rarely incurved, often ± accrescent; larger bracteoles narrowly oblong, abaxially villous. | C. ser. Molles |
7. Pomes bright pink to crimson, glabrous or pubescent at ends; flesh ± hard; fruiting sepals spreading or ± reflexed, not accrescent; larger bracteoles oblong to curved, abaxially glabrous. | C. ser. Dilatatae |
8. Petioles usually eglandular; if petioles ± glandular, sepal margins not glandular-denticulate, -serrate, or -laciniate | → 9 |
8. Petioles, at least some, glandular; sepal margins glandular-denticulate, -serrate, -laciniate, or -pectinate | → 33 |
9. Leaves: lobes 0 or not much bigger than teeth | → 10 |
9. Leaves: lobes evident and distinct | → 21 |
10. Bracteoles linear-filiform, margins eglandular or sparsely glandular; pomes 5–8 mm diam | C. ser. Virides |
10. Bracteoles narrowly elliptic, linear, or narrow, margins sparsely glandular; pomes 8–15 mm diam | → 11 |
11. Sepal margins entire or slightly glandular-serrate | → 12 |
11. Sepal margins glandular-serrate to glandular-laciniate or -pectinate | → 16 |
12. Leaf blades usually ± thin or chartaceous, matte | → 13 |
12. Leaf blades subcoriaceous, glossy | → 14 |
13. Inflorescence branches pubescent. | C. ser. Punctatae |
13. Inflorescence branches glabrous. | C. ser. Rotundifoliae |
14. Leaves and inflorescence branches glabrous. | C. ser. Crus-galli |
14. Leaves and inflorescence branches hairy, particularly young | → 15 |
15. Styles and pyrenes 1–3; se United States. | C. ser. Crus-galli |
15. Styles and pyrenes 3–5; Texas. | C. ser. Madrenses |
| C. persimilis |
| → 17 |
17. Leaf blades ± isodiametric, blue-green mature, woolly. | C. ser. Molles |
17. Leaf blades longer than wide, green to dark green mature, appressed- or scabrous-pubescent, glabrous, or white-tomentose | → 18 |
18. Leaves: veins 3 per side; stamens 15. | C. turnerorum |
18. Leaves: veins 4–7 per side; stamens 10 or 20 | → 19 |
19. Petiole length 20–30% blade; blades matte, villous to tomentose. | C. ser. Greggianae |
19. Petiole length usually 20–50% blade; blades glossy, glabrous or sparsely appressed-pubescent | → 20 |
20. Leaf blades scabrous, veins 5 or 6 per side; Texas. | C. ser. Madrenses |
20. Leaf blades glabrous, veins 7 per side; n United States, adjacent Canada. | C. ×sicca |
21. Inflorescence branches pubescent | → 22 |
21. Inflorescence branches glabrous | → 27 |
22. Bracteoles linear-filiform, margins eglandular or sparsely glandular. | C. ser. Virides |
22. Bracteoles linear to oblong, margins stipitate- or sessile-glandular | → 23 |
23. Sepal margins glandular-laciniate to -serrate; leaf blades hard, chartaceous, or coriaceous; fruiting sepals erect or erect-patent, sometimes spreading | → 24 |
23. Sepal margins entire or subentire; leaf blades thin; fruiting sepals erect-patent to recurved | → 25 |
24. Leaf blades broadly ovate or broadly elliptic to rhombic-elliptic, 2.5–4(–5) cm; flowers 15 mm diam.; c Texas, ± xeromorphs. | C. ser. Greggianae |
24. Leaf blades broadly elliptic to ovate, 4–8(–12) cm; flowers 18–22 mm diam.; e Texas to Alabama n to Minnesota and Quebec, mainly mesophytes. | C. ser. Molles |
25. Flowers (10–)13–17(–26) mm diam | C. ser. Tenuifoliae |
25. Flowers 18–23 mm diam | → 26 |
26. Fruiting sepals sessile. | C. ser. Punctatae |
26. Fruiting sepals elevated. | C. ser. Pruinosae |
27. Inflorescences (10–)15–30+-flowered, bracteoles linear-filiform (length/width = 10–20:1), margins eglandular or sparsely glandular; pomes 5–8 mm diam.; leaves with tufts of hair in abaxial vein axils (not discernable in rare pubescent form); southeastern, damp ground. | C. ser. Virides |
27. Inflorescences 3–15-flowered, bracteoles linear or narrowly elliptic, margins sessile- or stipitate-glandular; pomes 7–15(–20) mm diam.; leaves lacking tufts of hair in abaxial vein axils; topland species | → 28 |
28. Leaves: adaxial surfaces of young blades glabrous (except along veins in some taxa and on whole adaxial surface in C. virella); pomes pink, mauve, or pale green, sometimes scarlet, deep crimson, or purple, often strongly pruinose, flesh hard; fruiting sepals usually on prominent collar. | C. ser. Pruinosae |
28. Leaves: adaxial surfaces of young blades glabrous or sparsely hairy; pomes yellow to reddish mature, not strongly pruinose, flesh hard or mellow; fruiting sepals usually sessile, sometimes slightly elevated | → 29 |
29. Twigs 1–2-years old dark brown, dark purple-brown, or reddish brown to blackish, often ± pruinose | → 30 |
29. Twigs 1–2-years old not both purple-brown and ± pruinose | → 31 |
30. Leaves: veins 4–6 per side, blades 2.5–4(–5) cm; petioles eglandular, length 25–33% blade; stamens 10. | C. ser. Greggianae |
30. Leaves: veins 3–5(or 6) per side, blades 2–7 cm; petioles sparsely glandular, length 20–30% blade; stamens 10(or 20). | C. ser. Populneae |
31. Stamens 15, anthers purple; c Texas. | C. turnerorum |
31. Stamens 5–10 or 20, anthers pink to purple or ivory; e, n United States, adjacent Canada | → 32 |
32. Leaves: lobes well defined, lobe apices usually acute, blades 3–6(–8) cm, apices acute; petioles glandular or eglandular; anthers pink to red or purple; pomes red, ellipsoid to suborbicular, sepals erect-patent to recurved or erose. | C. ser. Tenuifoliae |
32. Leaves: lobe sinuses usually shallow, lobe apices subacute to obtuse, sometimes acuminate, blades 2–4(–5) cm, apices acuminate to obtuse; petioles eglandular or with 1–2 tiny glands; anthers ivory, sometimes pink; pomes usually bright to deep red or yellowish, sometimes orangish or burgundy, usually ± suborbicular, sometimes ellipsoid or oblong, sepals reflexed. | C. ser. Rotundifoliae |
33. Petioles, at least some, stipitate-glandular; bracteole margins usually short-stipitate- to stipitate-glandular | → 34 |
33. Petioles sessile-glandular; bracteole margins usually sessile-glandular to short-stipitate-glandular, except stipitate-glandular in ser. Intricatae, ser. Pulcherrimae, or C. dodgei group (larger bracteoles only, or some ser. Lacrimatae), rarely ± eglandular | → 40 |
34. Leaf blades ± elliptic to narrowly obovate or ovate, lobes 0 or obscure, subcoriaceous, (shiny at maturity); pomes orange-red to red, sepals not elevated on collar. | C. ser. Bracteatae |
34. Leaf blades broadly elliptic to elliptic, ovate or deltate, broadly ovate to rhombic-elliptic or rhombic, lobes 0 or 1–5 (if lobes 0, not elliptic to narrowly obovate), if so, short to moderately deep, usually ± thin, (not particularly shiny at maturity); pomes yellow to red, sepals ± elevated on collar, sometimes sessile | → 35 |
35. Pomes with sepals sessile; se United States | → 36 |
35. Pomes with sepals ± elevated on collar; e or se United States | → 37 |
36. Leaf blades 3–5 cm, elliptic to broadly elliptic or suborbicular, base rounded to broadly truncate, lobes 3 or 4 per side, distinct, veins 4 or 5 per side; inflorescence branches coarsely hairy. | C. ser. Populneae |
36. Leaf blades 2.5–4(–5) cm, ovate to obovate or rhombic-ovate, base ± cuneate, lobes 0 or 1–3 per side, obscure, veins 5 or 6(or 7) per side; inflorescence branches appressed-scabrous. | C. ser. Apricae |
37. Stamens 10; trunk bark fibrous, checked into longitudinal plates or corrugated; e United States to Missouri. | C. ser. Intricatae |
37. Stamens 20; trunk bark often corrugated; Texas to Georgia. | C. ser. Pulcherrimae |
38. Inflorescence branches hairy. | C. ser. Intricatae |
38. Inflorescence branches glabrous | → 39 |
| C. ser. Pulcherrimae |
| C. ser. Intricatae |
40. Twigs ± strongly flexuous, rarely slightly flexuous; leaf blades 1–4(–5) cm; (ultimate branches ± conspicuously pendulous, except in dwarf forms less than 10 dm) | → 41 |
40. Twigs straight, only rarely flexuous; leaf blades 2–6(–10) cm; (ultimate branches not especially drooping) | → 44 |
41. Dwarf species usually 0.5–2 m; twigs ± strongly flexuous, ultimate branches not markedly pendulous. | C. ser. Lacrimatae |
41. Larger species usually 2–7 m; twigs slightly to strongly flexuous, upper branches often ± pendulous | → 42 |
42. Leaf blades predominantly narrow, usually elliptic to oblong or narrowly obovate, sometimes obtrullate, ovate, or suborbicualte, usually widest toward tip, veins 1–5 per side (exiting mainly or wholly in apical part of blade), apices obtuse to acute; (upper branches conspicuously drooping). | C. ser. Lacrimatae |
42. Leaf blades suborbiculate to broadly ovate or rhombic-elliptic, veins 1–3 per side in small-leaved forms (1–2 cm), usually 3–5 per side in larger-leaved forms, terminating along leaf length, apices acute to obtuse; (upper branches gently to conspicuously drooping) | → 43 |
43. Leaves, especially young, glabrous or scabrous adaxially; (upper branches often slightly drooping, at most slightly flexuous); bracteoles ± stipitate-glandular; stamens 10 or 20, anthers ivory, cream, or pink to purple or red. | C. ser. Apricae |
43. Leaves, especially young, ± glabrous or woolly-tomentose adaxially; (upper branches drooping, clearly flexuous); bracteoles sessile- to short-stipitate-glandular; stamens 20, anthers ivory or cream. | C. ser. Lacrimatae |
44. Trunk bark smooth and exfoliating; pomes 4–6 mm diam | Crataegus (sect. Crataegus) ser. Microcarpae |
44. Trunk bark rough, scaly, fibrous, checked into longitudinal plates, or corrugated; pomes 8–14(–20) mm diam | → 45 |
45. Leaves: lobes 0 or shallow, sinuate; inflorescences 1–5-flowered; sepals ± equal to petals. | C. ser. Parvifoliae |
45. Leaves: lobes 0 or distinctly lobed; inflorescences 3–15-flowered; sepals shorter than petals | → 46 |
46. Stamens (10–)20; pomes pink, mauve, or pale green, sometimes scarlet, deep crimson, or purple, strongly pruinose, flesh ± hard. | C. ser. Pruinosae |
46. Stamens 10 or 20; pomes reddish or yellowish, seldom strongly pruinose, flesh ± hard to mealy | → 47 |
47. Stamens 13–18, anthers purple. | C. ser. Intricatae |
47. Stamens 5–10 or ca. 20, anthers white to cream or pale pink to pink-purple or red | → 48 |
48. Fruiting sepals elevated on short but distinct collar; glands of at least larger bracteoles clearly stipitate | → 49 |
48. Fruiting sepals sessile; glands of bracteoles sessile or stipitate | → 52 |
| C. ser. Intricatae |
| → 50 |
50. Inflorescence branches hairy; leaves 4–9 cm (rarely glabrous to sparsely hairy; if so, leaves 3–4 cm and anthers rose). | C. ser. Intricatae |
50. Inflorescence branches glabrous; leaves 4–9 cm (if 3–4 cm, anthers white to cream) | → 51 |
51. Fruiting sepals elevated on distinct collar; glands on all bracteoles stipitate; se United States. | C. ser. Pulcherrimae |
51. Fruiting sepals elevated on short collar; glands only on larger, lower bracteoles stipitate; midwestern United States and adjacent Canada. | C. ser. Rotundifoliae |
52. Anthers white to cream, rarely palest pink; bracteoles sessile- or stipitate-glandular | → 53 |
52. Anthers pale pink or pink to red or purple; bracteoles sessile- or very short-stipitate-glandular | → 56 |
53. Bracteoles sessile- or very short-stipitate-glandular; stamens 10 or 20; inflorescence branches glabrous or hairy | → 54 |
53. At least larger bracteoles stipitate-glandular; stamens 10; inflorescence branches glabrous | → 55 |
54. Young leaves: adaxial surfaces glabrous; stamens 10; Delaware. | C. ser. Populneae |
54. Young leaves: adaxial surfaces ± scabrous-hairy; stamens 10 or 20; n United States, s Canada. | C. ser. Rotundifoliae |
55. Shrubs or trees, 4–6 m; all bracteoles stipitate-glandular; Ozarks, possible for se United States. | C. ser. Intricatae |
55. Shrubs, 2–4 m; larger bracteoles stipitate-glandular; ne United States, adjacent Canada. | C. ser. Rotundifoliae |
56. Sepals glandular-denticulate; stamens 10; narrower pyrenes often concave-sided; pomes bright red in late August, becoming deep red at maturity; s Alberta, Saskatchewan. | Crataegus (sect. unassigned) ser. Montaninsulae |
56. Sepals usually glandular-serrate; stamens 10 or 20; all pyrenes plane-sided; pomes orange to vermillion or bright red, green, or dull red, becoming bright or deep red or burgundy at maturity; n, ne United States, s Canada | → 57 |
57. Anthers very pale pink or pale cream-pink; inflorescence branches glabrous | → 58 |
57. Anthers pink to pink-purple or red; inflorescence branches glabrous or hairy | → 59 |
58. Anthers pale cream-pink; stamens 10; mature fruit orange to orange-brown or orange-red; Ozarks, possible for se United States. | C. ser. Intricatae |
58. Anthers very pale pink; stamens 20; mature fruit burgundy; British Columbia. | C. ser. Rotundifoliae |
59. Inflorescence branches glabrous. | C. ser. Populneae |
59. Inflorescence branches hairy | → 60 |
60. Shrubs 4–10 m; leaves 5–9 cm; lobes usually shallow, but if deeper, broad; flowers 16–22 mm diam.; fruits 10–14 mm; Great Lakes to New England s in Appalachians to North Carolina. | C. ser. Coccineae |
60. Shrubs 3–5 m; leaves 3–7 cm; lobes moderately deep, acute; flowers 13–17 mm diam.; fruits 8–10 mm; se Canada, ne United States | → 61 |
61. Leaf blades usually thin, often glossy, apices acute, lobe apices acuminate; inflorescence branches villous; sepal margins usually glandular-serrate, rarely nearly entire and eglandular; styles 3–5; pomes ellipsoid. | C. ser. Tenuifoliae |
61. Leaf blades thin to chartaceous, matte, apices and lobe apices acute to subacute; inflorescence branches densely pubescent or villous; sepal margins glandular-serrate; styles 3 or 4(or 5); pomes suborbicular. | C. ser. Rotundifoliae |