Flora of North America species comparison

Crataegus castlegarensis occurs from around the northern Okanagan, British Columbia, to the northern California Coast Ranges, to northwestern Montana, and the Rocky Mountains to northeast of Salt Lake City, Utah. The species occurs also in the Cypress Hills of Alberta and Saskatchewan; it is found in habitats similar to those of C. douglasii and is at least as abundant as that species in a number of parts of its range.

Crataegus castlegarensis is readily recognized by a combination of hairy inflorescence branches, pomes more or less orbicular, crimson or burgundy (with irregular earlier ripening) around the third week of August, soon becoming purple, often when nearby C. douglasii is already black, as well as a tendency to possess thorns on the young twigs branched at the base to become double, triple, or even sometimes quadruple. Such multiple thorns, though sometimes abundant on a bush, are more often few and may require searching for. Inflorescence pubescence, as in other species with this characteristic, may become sparse by fruiting. Crataegus castlegarensis is most similar to C. douglasii; its fruit is usually more orbicular, even oblately so, than is normal in that species, sometimes even with a recessed junction to the pedicel like an apple.

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

Of conservation concern.

Crataegus flava ranges from southeastern Georgia to South Carolina and northern Florida. Wild specimens of the typical form have not been seen since the early 1900s; vegetative specimens resembling this species were collected from the Florida panhandle in the early part of the present century.

Crataegus flava has been widely confused with members of both ser. Apricae and ser. Lacrimatae (J. B. Phipps et al. 2007). Its stamen number has been wrongly credited as 10 or 20; stamen number in the type has recently been verified as 13–16 by S. Landrein (Kew). Recent collections with 13–16 stamens are unknown. The correct stamen counts are unusual for Crataegus, which are mainly narrowly dispersed around modes of 10 or 20, so this perhaps suggests, together with its somewhat flexuous twigs, and rarity, hybrid origin. Crataegus flava is similar to C. rubella, particularly in fruit shape and color as well as general glandularity, so its placement with members of sect. Intricatae seems appropriate. Lack of recent collections similar to the type suggests that modern attributions to C. flava may represent hybrids involving members of ser. Apricae.

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