Flora of North America species comparison

Rumex persicarioides often has been treated by American botanists as a variety or synonym of R. maritimus (see R. S. Mitchell 1978). It and R. fueginus differ from Eurasian R. maritimus in many respects and are as distinct as many widely recognized Eurasian taxa of this aggregate (e.g., R. palustris, R. rossicus Murbeck, R. ucranicus Fischer ex Sprengel, R. marschallianus Reichenbach, R. amurensis Fr. Schmidt ex Maximowicz, R. evenkiensis Elisarjeva). When submerging R. persicarioides as a variety of R. maritimus, Mitchell noted: “Taxonomic treatment of the group from a Eurasian point of view would undoubtedly shed light on the minor problems which we face in North and South America.” However, from a Eurasian point of view (see e.g., K. H. Rechinger 1937, 1949; J. E. Lousley and D. H. Kent 1981; N. N. Tzvelev 1989b), all North American native taxa of subsect. Maritimi are evidently specifically different from any native Eurasian ones (with the only possible exception of Pacific plants, which are discussed below).

Plants similar to Rumex persicarioides, but with bigger tubercles and occuring along the Pacific coast from northern California to British Columbia, are, in my opinion, closer to R. fueginus in their habit and vegetative characters. K. H. Rechinger (1937) provisionally determined such specimens as R. persicarioides. J. E. Dawson (1979) noted that the Pacific plants differ from Atlantic ones in having bigger tubercles (more than 1.9 × 0.7–1 mm in western plants; less than 1.9 × 0.7 mm in eastern R. persicarioides in the narrow sense), and described these large-tubercled plants as a distinct variety, “R. maritimus var. pacificus���, unfortunately, an invalid name. However, that taxon seems to be extremely closely related to or possibly conspecific with the northeastern Asian species, R. ochotskius Rechinger f., which is known in eastern Asia from northern Japan to the Okhotsk Sea region of Russian Far East (especially Sakhalin and Kuril islands). The latter species also has large (to 2–2.5 mm) botuliform tubercles with obtuse apices. In the original description Rechinger stated: “…foliorum forma R. maritimo simillimus…,” but N. N. Tzvelev (1989b) in his recent treatment of the genus in the Russian Far East noted that most of the specimens of R. ochotskius seen by him had leaf blades rotundate-truncate or broadly cuneate at the base. The R. persicarioides-like plants from the Pacific coast of the United States and Canada (as well as their most probable allies from eastern Asia) need additional study. At present I prefer to place them provisionally into R. persicarioides, following Rechinger’s treatment.

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

Rumex dentatus, belonging to subsect. Dentati Rechinger f. (K. H. Rechinger 1937), is an extremely variable species. In Eurasia and northern Africa it is represented by several distinct races, usually regarded as subspecies. Rechinger reported from North America (California and Oregon, mostly as a casual alien occuring in ballast grounds) only subsp. klotzschianus (Meisner) Rechinger f., which is native in southern and eastern Asia (China, India, Japan, Korea). J. E. Dawson (1979) also regarded this as the most common subspecies in North America. However, I believe most North American representatives of this aggregate belong to subsp. halacsyi (Rechinger f.) Rechinger f., which is native in the eastern Mediterranean region (Asia Minor), the Caucasus, southeastern Europe, and western and central Asia. This subspecies, sometimes recognized as R. halacsyi Rechinger f., differs from subsp. klotzschianus by its broader triangular (not rounded) inner tepals and longer teeth (to 3 mm). Unfortunately, subspecies of R. dentatus still are insufficiently understood even in Eurasia. It would be premature to assign most North American specimens to any infraspecific entity.

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