Crataegus (sect. Coccineae) ser. Rotundifoliae
Man. Cult. Trees ed. 2, 363. 1940.
Shrubs, sometimes trees, (15–) 20–60 (–70) dm, often multistemmed. Stems: trunk bark buff to darker, fibrous, checked into longitudinal plates, freshly exposed bark orangebrown; branches spreading; twigs ± straight, new growth green to reddish, pubescent or glabrous, 1-year old usually golden green to tan, sometimes deep reddish-brown or gray-brown, older graying; thorns on twigs usually numerous, usually ± recurved, sometimes straight, 1-year old usually shiny, dark-brown or blackish, older graying, ± stout to ± slender, 2.5–5 (–7) cm. Leaves: petiole length 28–60% blade, winged, glabrous or pubescent, distally variably sessile-glandular; blade mid to dark green or blue-green, matte, usually ± rhombic, sometimes ovate, elliptic-oblong, or suborbiculate, 2–6 (–9.5) cm, thin to chartaceous, sometimes subcoriaceous, base cuneate to rounded, truncate, or broadly ovate, lobes 0, or 1–5 (or 6) per side, sinuses shallow to deep, lobe apex subacute to obtuse, sometimes acuminate, margins serrate, sometimes crenate, teeth gland-tipped, venation craspedodromous, veins (3–) 5 or 6 (–8) per side, apex acuminate to obtuse, abaxial surface usually glabrous young, sometimes persistently hairy, adaxial usually scabrous, glabrescent, sometimes persistently scabrous or glabrate. Inflorescences (1–) 4–15 (–20) -flowered, convex panicles; branches densely pubescent, sometimes glabrous; bracteoles caducous, usually numerous, linear or narrowly elliptic, usually membranous, sometimes subherbaceous, margins sessile-glandular, sometimes stipitate-glandular larger bracteoles. Flowers (8–) 12–20 mm diam.; hypanthium obconic, densely pubescent, sometimes glabrous; sepals narrowly triangular, 1/2–2/3 petal length, margins entire or slightly glandular-serrate, apex usually obtuse, sometimes acute, abaxially pubescent or glabrous; stamens (5–) 10 or (18–) 20, anthers ivory, sometimes pink; styles 2–4 (or 5). Pomes usually bright to deep red or yellowish, sometimes orangish or burgundy, usually ± suborbicular, sometimes ellipsoid or oblong, (7–) 8–12 (–14) mm diam., glabrous or pubescent; flesh mealy; sepals sessile except in C. margarettae, remnants erect-patent to reflexed, nonaccrescent; pyrenes 2–4 (or 5), sides plane, sometimes shallowly concave in 101. C. ursopedensis, dorsally grooved.
Species 8 (8 in the flora).
Series Rotundifoliae ranges from southern interior British Columbia to Newfoundland, south to Oregon, Colorado, the northern Great Plains, the Midwest, the southern Great Lakes, New England, and mid latitude Appalachians. East of the Rocky Mountains, ser. Rotundifoliae is the most northerly series of Crataegus and only ser. Macracanthae has as great an east-west range. The most wide-ranging species are C. chrysocarpa, ranging from nearly the Pacific to the Atlantic, C. margarettae, midwestern, and C. dodgei, common mainly from the Great Lakes to New England.
Plants of ser. Rotundifoliae are relatively small shrubs that are almost never treelike; their inflorescences are quite copiously glandular-bracteolate, at least when young. Putative hybrids with series other than ser. Macracanthae are rare.
Series Rotundifoliae comprises two main groups plus the somewhat atypical Crataegus ursopedensis. The first group comprises the C. chrysocarpa complex, the second, C. margarettae and C. dodgei. Members of the C. chrysocarpa complex have relatively small, more or less ovate to rhombic-ovate, acute-tipped, sharply lobed leaves with glandular petioles and gland-tipped teeth. They also tend to have bracteoles with sessile glands and stouter thorns than members of the second group. The group occurs mostly in northern intermontane, Great Plains, and deciduous forest-conifer transition zone. It is also more xeromorphic, the plants typically being shrubs of dryish areas in the west and often on thin or rocky soils in the east. They usually have pubescent inflorescences and red mature pomes. Members of the second group, around C. margarettae and C. dodgei, are less glandular and often have more or less obtuse-tipped leaves, finer and often fewer thorns, larger, glabrous inflorescences, basal bracteoles that are often prominently stipitate-glandular, and a strong tendency to bear yellowish pomes. This group is more southerly.
Members of the chrysocarpoid group of ser. Rotundifoliae can be difficult to distinguish from members of ser. Intricatae. Nearly all members of ser. Intricatae have a somewhat elevated calyx in fruit; their distribution is almost entirely south of Crataegus chrysocarpa in eastern North America, and they often have stipitate-glandular bracteoles. Crataegus submollis (ser. Molles), apart from being larger in all its parts and having more persistent bracteoles, is also sometimes difficult to differentiate from C. chrysocarpa and might key out under ser. Rotundifoliae, as might also C. flabellata (ser. Tenuifoliae). The inter-relationships of the taxa mentioned require deeper investigation; consequently, the key to species includes C. padifolia (ser. Intricatae) and C. submollis (ser. Molles) in the fourth and thirteenth couplets, respectively. The interserial hybrid C. ×sicca keys out in part in the fifth and fifteenth couplets, and C. laurentiana keys out in the eighth couplet.
|1||Inflorescence branches glabrous or sparsely pilose young||> 2|
|1||Inflorescence branches pubescent, sparsely to densely villous, or pilose||> 7|
|2||Stamens (18–)20||> 3|
|2||Stamens (5–)10(or 20)||> 4|
|3||Petioles sparsely to densely persistently glandular; leaf blades ± rhombic, lobes 2–4 per side, max LII 20%, lobe apices acute, apices acuminate, veins 4 or 5 per side, green mature; sw Canada.||Crataegus sheila-phippsiae|
|3||Petioles usually with small glands at first, becoming eglandular; leaf blades suborbiculate, ovate, or obovate, rarely elliptic-rhombic to elliptic or lance-elliptic, lobes 1–3(or 4) per side, sinuses usually shallow, sometimes deep, lobe apices obtuse to angled, apices subacute to obtuse, veins 3 or 4 per side, green to bluish green; c, e North America.||Crataegus margarettae|
|4||Petioles sparsely glandular; bracteole margins stipitate-glandular; pomes ± oblong, 12–14 mm diam.; Ozarks.||Crataegus padifolia (ser. Intricatae)|
|4||Petioles eglandular or with few, very tiny glands; at most, larger bracteoles only sometimes with margins stipitate-glandular; pomes usually suborbicular, 7–12 mm diam||> 5|
|5||Flowers 10–14 mm diam.; styles and pyrenes 3–5.||Crataegus ×sicca|
|5||Flowers 13–20 mm diam.; styles and pyrenes 2–4(or 5)||> 6|
|6||Leaf blades broadly rhombic-ovate, 4–5 cm; bracteoles: larger with margins sessile-glandular; sepal margins glandular-serrate; pomes red.||Crataegus chrysocarpa|
|6||Leaf blades suborbiculate, ± ovate, broadly rhombic to rhombic-ovate, sometimes broadly elliptic, 2–5 cm; bracteoles: some with margins stipitate-glandular; sepal margins entire or ± glandular-denticulate; pomes yellow to yellow-orange, dull orange, or ruddy to red.||Crataegus dodgei|
|7||Anthers pink or rose||> 8|
|7||Anthers white to cream, sometimes pale yellow||> 9|
|8||Leaf surfaces: adaxial short-appressed pubescent young; petiolar glands caducous, (dark); stamens 10; styles 3–5; pomes oblong to pyriform; pyrene sides irregularly eroded or pitted.||Crataegus laurentiana|
|8||Leaf surfaces: adaxial appressed-scabrous, glabrescent, or short-appressed-pubescent; petiolar glands persistent; stamens 10 or 20; styles 3 or 4(or 5); pomes suborbicular; pyrene sides plane.||Crataegus chrysocarpa|
|9||Stamens 20||> 10|
|9||Stamens 10||> 13|
|10||Petioles usually with small glands at first, becoming eglandular; leaf blades suborbiculate, ovate, or obovate, rarely elliptic-rhombic to elliptic or lance-elliptic, apices subacute to obtuse, lobe apices obtuse to angled, veins 3 or 4 per side, green to bluish green; sepal margins entire or subentire; pomes yellow, red, or dull burgundy; c, e North America.||Crataegus margarettae|
|10||Petioles persistently glandular; leaf blades broadly rhombic-ovate to broadly ovate to oblong-ovate or broadly elliptic, apices acute, lobe apices acute or triangular, veins 3–8 per side, green; sepal margins glandular-serrate; pomes red; n United States, s Canada||> 11|
|11||Leaf blades ovate-oblong to oblong, (4–)5–7(–8) cm, (on extension shoots similar, larger), lobes 5 or 6 per side, veins 5–7 per side.||Crataegus irrasa|
|11||Leaf blades rhombic-ovate to ovate or broadly ovate, oblong-ovate, or broadly elliptic, 2–5(–7.5) cm, (on extension shoots similar or suborbiculate, larger), lobes 2–5(or 6) per side, veins 3–5(–8) per side||> 12|
|12||Leaf blades rhombic-ovate to ovate, (on extension shoots similar shape, larger), lobes 2–4(–6) per side, sinuses moderately deep, veins 3–5(–7) per side.||Crataegus chrysocarpa|
|12||Leaf blades broadly ovate to oblong-ovate or broadly elliptic, (on extension shoots usually suborbiculate, larger), lobes 4 or 5 per side, sinuses shallow, veins 6–8 per side.||Crataegus oakesiana|
|13||Plants 60–70 dm; petioles strongly glandular; larger bracteoles subherbaceous; flowers 20–22 mm diam.; styles and pyrenes 3–5; pomes 10–15 mm diam.; fruiting sepals stiff, erect-patent; Great Lakes to New England.||Crataegus submollis (ser. Molles)|
|13||Plants 20–50 dm; petioles ± glandular or eglandular; larger bracteoles membranous; flowers 13–20 mm diam.; styles and pyrenes 2–4(or 5); pomes 7–12 mm diam.; fruiting sepals thin, spreading to reflexed or patent to ± appressed||> 14|
|14||Leaves at early anthesis strikingly flabellate, only 1–2 cm, 5.5–9.5 cm, glossy and subcoriaceous mature; thorns (3–)4–7 cm; bracteoles cream to pale green, often suffused light red especially distally.||Crataegus ursopedensis|
|14||Leaves at early anthesis slightly or not flabellate, much larger than an open flower, 2–5(–7.5) cm, matte and thin to chartaceous mature; thorns 2.5–6(–7) cm; bracteoles usually hyaline||> 15|
|15||Leaves 2–3 cm; bracteoles reddish; flowers 18–20 mm diam.; pomes pale orange, strongly pruinose.||Crataegus ×sicca|
|15||Leaves 2–5(–7.5) cm; bracteoles usually hyaline; flowers 13–20 mm diam.; pomes yellowish or orangish to ruddy, scarlet, or red, not pruinose||> 16|
|16||Bracteole margins sessile-glandular; sepals 4 mm, triangular, margins glandular-serrate; pomes scarlet to deep red.||Crataegus chrysocarpa|
|16||Bracteole margins of larger ones ± stipitate-glandular; sepals 5 mm, narrowly triangular, margins entire, glandular; pomes yellowish, dull orange, or reddish.||Crataegus lumaria|