75d. Crataegus pruinosa (H. L. Wendland) K. Koch var. rugosa (Ashe) Kruschke, Publ. Bot. Milwaukee Public Mus. 3: 181. 1965.
Crataegus rugosa Ashe, J. Elisha Mitchell Sci. Soc. 17: 5. 1900; C. leiophylla Sargent; C. mackenziei Sargent ex Mackenzie; C. rubicundula Sargent; C. seclusa Sargent; C. seducta Sargent
Shrubs or trees, 20–40(–70) dm, ˂usually branched to base˃. Leaves: blade broadly ovate to deltate, 3–7 cm, length/width = 1–1.2, lobes 2–4 per side, distinct, lobe apex acute, base very broadly cuneate or truncate to weakly subcordate, adaxial surface glabrous, sometimes sparsely appressed-hairy along veins. Inflorescence branches glabrous. Flowers 15–22 mm diam.; stamens 20, anthers pale pink.
Flowering Apr–May; fruiting Sep–Nov. Open scrub, light woodland shade; 50–300 m; Ont.; Ill., Ind., Iowa, Ky., Mich., Mo., N.Y., N.C., Ohio, Pa., Tenn., Wis.
Variety rugosa is fairly common from Missouri to the mountains of North Carolina, then northward through the range of the species. The variety often has the most proportionately wide and most deeply incised leaves of the Crataegus pruinosa group. The leaves also characteristically have sharper and longer marginal teeth than other varieties. Extremes are C. mackenziei with acute lobes and C. seducta with rather obtuse lobes.
Unnamed plants of the southern Appalachian piedmont, very likely worthy of at least varietal rank, will key here and are differentiated from var. rugosa as follows: leaf blade 4–6 cm (3–7 cm in var. rugosa), laminas thin (finally chartaceous to somewhat coriaceous in var. rugosa), basal corners of leaf rounded, bases often subcordate (not conspicuously rounded, bases rarely subcordate in var. rugosa).