Flora of North America species comparison

Varieties 6 (6 in the flora).

Crataegus pruinosa extends from Arkansas to Wisconsin, through the southern Great Lakes to southern New England, and, in the south, mainly in the Appalachians to northern Georgia.

In the north of its range, Crataegus pruinosa is mainly a shrub of open successional habitats but in the south may commonly be a taller tree of open or thin woodlands.

Many hawthorns have a little waxy bloom on their pomes; it is particularly prominent on Crataegus pruinosa and C. cognata compared to others. Some authors include in C. pruinosa their white-anthered counterparts, here assigned to C. cognata. Whereas C. pruinosa characteristically has entire or subentire sepal margins, some forms in the southwest of the range of the species (for example, C. calliantha Sargent, C. seducta Sargent) may have glandular-serrate sepal margins. They may represent introgression with C. coccinioides. The varieties of C. pruinosa are weakly differentiated from each other, most of them on leaf shape and size characters. The more widespread varieties constitute a range of morphotypes held together by common traits. Crataegus gaudens Sargent is a strikingly distinct form from Pennsylvania that has more or less elliptic leaves with lobes absent; it is clearly related to C. pruinosa. Note that 159. Crataegus ×coleae, a Michigan endemic, will key out here if its laterally scarred pyrenes are missed.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Crataegus uniflora is widespread in the southeastern United States from Long Island (New York) to eastern Texas; it is most abundant in the coastal plain and lower piedmont. A disjunction in the Mississippi embayment between trans-Mississippian and cis-Mississipian populations mirrors a similar pattern in C. spathulata (J. B. Phipps 1998).

Crataegus uniflora is usually easy to identify because of its small size, leaves small and coriaceous with lobes absent, numerous straight, fine thorns, inflorescences uniflorous or few-flowered, sepals glandular-pectinate and equal to or longer than the petals, anthers white to cream, and pomes yellowish to ruddy. Possible confusion with some members of ser. Lacrimatae is treated under the series discussion. Sterile plants might be confused with small, sterile ones of C. berberifolia (ser. Crus-galli) except for the smaller number of lateral veins on the leaves. An interesting feature of C. uniflora is the occasional deep lobing of extension-shoot leaves, even narrow ones, with veins to sinuses.

Crataegus uniflora is somewhat variable in plant size, leaf shape, number of flowers to an inflorescence (though commonly one), and anther color (usually ivory to cream). The typical form, which is common, has 1- or 2-flowered inflorescences, and is usually a small shrub with more or less spatulate to narrowly obovate leaves. Some particularly dwarf forms of this, on laterite soil in Georgia, have been observed with over 100 flowers when less than 3 dm.

Forms of Crataegus uniflora with 3–6-flowered inflorescences are also common and are represented by C. parvifolia and C. trianthophora. These are connected to the typical uniflorous kind by numerous intermediates and may be distinguished from the related C. brittonii by their smaller and narrower leaves with lobes absent.

Three anomalous variants, very similar or identical to Crataegus uniflora except for possessing small, more or less unlobed but glandular-serrate sepals, are known. These are: C. croomiana Sargent from northern Florida, C. bisulcata Ashe from North Carolina, and C. grossiserrata Ashe from Florida. The first, also best known, is further distinguished by pink anthers, the second by broader leaves, and the third by often orbiculate (unusual for ser. Parvifoliae) extension-shoot leaves with a tendency to deep lobing sometimes with veins to sinuses, and particularly strong and sharp leaf teeth. All suggest hybrid origin with ser. Lacrimatae.

(Discussion copyrighted by Flora of North America; reprinted with permission.)