Crataegus (sect. Macracanthae) ser. Macracanthae

Man. Cult. Trees ed. 2, 368. 1940.

Endemic
Basionym: Crataegus sect. Macracanthae Loudon Arbor. Frutic. Brit. 2: 819. 1838
Treatment appears in FNA Volume 9. Treatment on page 516. Mentioned on page 522, 525, 594, 605, 640, 643.

Shrubs or trees, 20–70 (–80) dm. Stems: 1–2-year old twigs usually very dark; thorns on twigs ± stout. Leaves: petiole glandular or eglandular; blade usually rhombic to rhombic-elliptic or broadly elliptic to ovate, lobes 0 or 3–5 (–8) per side, lobe apex acute to obtuse, venation craspedodromous, veins (3–) 6–8 per side, adaxial surface scabrous-pubescent young, glabrescent. Inflorescences (5–) 12–30-flowered; bracteoles caducous, membranous, margins sessile or stipitate-glandular. Flowers (12–) 13–19 (–22) mm diam.; sepal margins glandular-denticulate to glandular-laciniate, rarely nearly entire; stamens 7–10 or 20; styles 2 or 3 (–5). Pomes orange to red, broadly ellipsoid to suborbicular, glabrous or hairy; pyrenes 2 or 3 (–5), sides eroded.

Discussion

Species 5 (5 in the flora).

Three common core species comprise ser. Macracanthae: the similar Crataegus macracantha and C. succulenta and the somewhat dissimilar C. calpodendron. These are notable for their mid late to very late anthesis compared to sympatric hawthorns, stout thorns, and eglandular petioles. Crataegus sheridana and C. rubribracteolata are placed here for convenience, may not be closely related, and perhaps would better sit with ser. Anomalae. Series Macracanthae is one of only two series of red-fruited hawthorns in North America that has eroded pyrenes.

Members of ser. Macracanthae form putative hybrids with members of ser. Crus-galli (Crataegus persimilis), ser. Parvifoliae (C. ×vailiae), ser. Pruinosae (C. chadsfordiana Sargent), ser. Punctatae (C. florifera), and ser. Rotundifoliae (C. laurentiana), at least. Some are treated here as interserial hybrid species numbers 154–169; C. laurentiana, C. persimilis, and C. ×vailiae key out in the eighth, first, and second couplets, respectively.

Selected References

None.

Key

1 Leaves: adaxial surfaces glabrous or glabrate, glossy, lobes 0, or 3 or 4 per side. Crataegus persimilis
1 Leaves: adaxial surfaces pubescent young, matte, lobes 0 or (1–)3–5(–8) per side > 2
2 Inflorescences 2–8(–20)-flowered; sepals ± equal to petals, margins glandular-laciniate. Crataegus ×vailiae
2 Inflorescences (5–)12–30-flowered; sepals shorter than petals, margins usually glandular-denticulate to glandular-laciniate > 3
3 Petioles eglandular, rarely glandular on distal wing > 4
3 Petioles ± sessile-glandular > 6
4 New growth pubescent; thorns on twigs absent or numerous; leaves (often yellowish green, without impressed venation), abaxial surfaces persistently appressed-pubescent; sepal margins nearly entire or shallowly glandular-serrate; (anthesis 1–3 weeks after sympatric species of this series); stamens 20. Crataegus calpodendron
4 New growth glabrous; thorns on twigs usually numerous; leaves (often blue-green, with impressed venation), abaxial surfaces glabrous (except the pertomentosa form of C. macrantha); sepal margins glandular-serrate to glandular-laciniate; (anthesis 1–3 weeks before C. calpodendron in same locality); stamens 10 or 20 > 5
5 Stamens 20; anthers 0.5–0.7 mm. Crataegus succulenta
5 Stamens 10; anthers 0.9–1.2 mm. Crataegus macracantha
6 Pyrene sides pitted or ± deeply concave > 7
6 Pyrene sides ± roughened with irregular pitting or diagonal scarring > 8
7 Leaf blade sinuses obscure to well-marked, LII 5–15%, lobe apices usually obtuse; pyrene sides pitted; (anthesis late among sympatric hawthorns); bracteoles in young inflorescences ± pallid; anthers white or pink; nw Montana. Crataegus macracantha
7 Leaf blade sinuses moderately deep, max LII 25–33%, lobe apices acute to acuminate; pyrene sides ± deeply concave; (anthesis one of two earliest sympatric hawthorns); bracteoles in young inflorescences deep orange-red or fading; anthers ivory or cream; Cypress Hills, Alberta, Saskatchewan. Crataegus rubribracteolata
8 Leaf blade lobe apices acute and sinuses shallow, LII 5–15%, or lobe apices subacute, sinuses deeper, LII 15–30%; anthers ivory; Great Plains. Crataegus sheridana
8 Leaf blade lobe apices acute and sinuses moderately deep, LII 20–33%; anthers cream or pale pink; Minnesota, Maine, Michigan, Wisconsin, to Quebec and Newfoundland. Crataegus laurentiana
glabrescent +  and scabrous-pubescent +
0.8 cm8 mm <br />0.008 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
cream +, ivory +, white +, pink +  and red +
James B. Phipps +
Loudon +
compound +  and simple +
opposite +  and alternate +
Crataegus sect. Macracanthae +
less ovate or rhombic-elliptic +  and rhombic-elliptic +
8 cm80 mm <br />0.08 m <br /> (12 cm120 mm <br />0.12 m <br />) +
broadly elliptic to ovate +, rhombic to rhombic-elliptic +  and rhombic +
2 cm20 mm <br />0.02 m <br /> (8 cm80 mm <br />0.08 m <br />) +
adnate +  and distinct +
crowded +, scattered +  and alternate +
North America +
not +  and aggregated +
1.3 cm13 mm <br />0.013 m <br /> (1.9 cm19 mm <br />0.019 m <br />) +
unisexual +  and bisexual +
not +  and aggregated +
not +  and aggregated +
yellow +  and red or purplish +
0.6 cm6 mm <br />0.006 m <br /> (2 cm20 mm <br />0.02 m <br />) +
tomentose +  and glabrous +
constricted +
0.2 cm2 mm <br />0.002 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
(5-)12-30-flowered +
crassinucellate +
deciduous +
craspedodromous +
entire +  and serrate +
stipitate-glandular +
serrate +  and crenate +
inferior +  and superior +
biseriate +  and clustered +
collateral +  and basal +
0.8 cm8 mm <br />0.008 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
elliptic +  and circular +
0 (?) +  and 4 (?) +
free +  and distinct +
post-mature +
eglandular +  and glandular +
adnate +, free +, connate +  and distinct +
dark gray-brown +  and russet +
exfoliating +  and corrugated +
orange +  and red +
hairy +  and glabrous +
broadly ellipsoid +  and suborbicular +
Man. Cult. Trees ed. +
not arillate +
persistent +
free +  and distinct +
glandular-denticulate +  and glandular-laciniate +
appressed +  and erect +
triangular +
1-50-flowered +  and few-leaved +
eroded +  and pitted +
free +  and distinct +
branched +  and simple +
persistent +
distinct +
exsert +  and lateral +
elongate +
glabrous +  and tomentose +
Crataegus (sect. Macracanthae) ser. Macracanthae +
Crataegus sect. Macracanthae +
6 cm60 mm <br />0.06 m <br /> (10 cm100 mm <br />0.1 m <br />) +
slender +
1 cm10 mm <br />0.01 m <br /> (6 cm60 mm <br />0.06 m <br />) +
craspedodromous +  and gland-tipped +
inconspicuous +
less erect +  and oblique +
1 +  and several +
determinate +
6 +  and 8 +
tree +  and shrub +