Crataegus sect. Anomalae Sargent ex Eggleston in B. L. Robinson and M. L. Fernald, Manual ed. 7, 477. 1908; Crataegus ser. Brainerdianae Eggleston ex E. J. Palmer

Shrubs or trees, 30–70 dm. Stems: 2-year old twigs ˂shiny˃, dark or reddish brown; thorns on twigs stout to ± slender. Leaves: petiole eglandular or glandular; blade ± ovate, coriaceous to thin, lobes 3–5 per side, lobe apex ± acute, venation craspedodromous, veins 5 or 6(–8) per side, adaxial surface glabrous or appressed-pubescent. Inflorescences 6–12-flowered; bracteoles caducous, membranous, margins sessile-glandular. Flowers 15–20 mm diam.; sepal margins subentire or glandular-serrate; stamens 7 or 8(–10) or 20; styles 2–4(or 5). Pomes reddish or orange-red, usually suborbicular, sometimes ± oblong-orbicular, glabrous or hairy; pyrenes 2–4, sides ± plane to erose or pitted.

Species 3 (3 in the flora): North America.

Members of ser. Anomalae are locally common hawthorns found from west of Lake Michigan to the Atlantic in Massachusetts and New Hampshire. Some members of the series are plausibly of hybrid origin, and if so, a member of ser. Macracanthae is always one parent, the other perhaps being either ser. Punctatae (Crataegus florifera) or ser. Tenuifoliae (most taxa, for example, C. oreophila Lance). Crataegus ×vailiae, usually treated with ser. Macracanthae, may also key here. Other (very rare or even extinct) putative hybrids that might be referred to ser. Anomalae include: C. chadsfordiana Sargent and C. spatiosa Sargent (ser. Pruinosae × ser. Macracanthae), C. desueta Sargent (C. punctata × ser. Anomalae), C. dunbarii Sargent and C. ideae Sargent (ser. Anomalae × ser. Rotundifoliae), C. kennedyi Sargent (C. jesupii × ser. Anomalae), C. randiana Sargent and C. rubrocarnea Sargent (ser. Anomalae × C. macrosperma), C. websteri Sargent (ser. Anomalae × ser. Macracanthae), C. harryi Sargent and C. shirleyensis Sargent (ser. Anomalae × ser. Punctatae), without precise parentage suggested [putative parents as suggested by E. J. Palmer (1952) are given parenthetically]. The very local and perhaps extinct C. kingstonensis Sargent is perhaps a hybrid of ser. Anomalae × C. pruinosa.

The interserial hybrids Crataegus ×bicknellii and C. ×coleae key out in the second couplet; C. ×vailiae keys out in the fifth couplet.