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 calpodendron is most common in the northern and Appalachian part of its range, where it is more likely to grow in the open (shrubs to 50 dm); in the southern part of its range, it is often in shaded habitats (trees to 70 dm). The distinctive vase-shaped branching pattern of well-grown northern C. calpodendron makes it easily distinguished even in winter, the lack of a central dominant trunk and the arching side trunks being characteristic. In open areas in the northern part of its range, mature leaves of C. calpodendron are often somewhat coriaceous and keeled along the midvein. In the south, the leaves remain thin until maturity. It is the second latest native hawthorn to flower, usually mid June (north) and early May (south, for example, central Alabama).

Vegetatively, distinction between Crataegus calpodendron and C. succulenta or C. macracantha is best supported by the more strongly impressed leaf venation, usually glabrous abaxial leaf surfaces, dark purple-brown, shiny, one-year twigs, and often longer and stouter thorns in the latter.

Crataegus calpodendron is variable in branching pattern, indumentum, and leaf and fruit shapes. Examination of a large number of specimens does not reveal discontinuities between leaf shapes, neither do these shapes correlate with the varieties hitherto recognized primarily on fruit characteristics. In general, C. calpodendron in the narrow sense, C. globosa, C. mollicula, and C. mollita represent forms with narrower, rhombic-elliptic, less deeply incised leaves with somewhat blunter lobes and teeth; C. hispidula, C. insperata, and C. obscura represent forms with nearly isodiametric leaves, the deepest and sharpest sinuses, and the biggest and sharpest teeth; C. scabera and C. spinulosa are intermediate. Smaller leaf and pome sizes are more common in drier or hotter terrain.

Crataegus ×rupicola Sargent (synonym of C. harveyana Sargent), from Missouri, represents a form with glands at the base of the leaf and on the petiole and perhaps is not pure calpodendron. Crataegus warneri Sargent from east-central Texas is provisionally placed here, although it could be a hybrid or hybrid derivative of C. calpodendron × C. crus-galli or an odd form of C. ashei with ten stamens and red anthers. Crataegus warneri has broadly ovate leaves 3.5–5 cm and appears to be somewhat xeromorphic; it is distinguishable from other forms of C. calpodendron with similar leaves only by its ten stamens and lack of pitted pyrenes. Crataegus ×simulata Sargent, from Missouri, is a probable hybrid of C. calpodendron with C. reverchonii var. palmeri (as C. palmeri) according to E. J. Palmer (1952). Crataegus ×vailiae is the most convincing hybrid of C. calpodendron (with C. uniflora; see Interserial Hybrids).

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