Flora of North America species comparison

In habit, Rubus ursinus is often reminiscent of the predominantly eastern North American, non-sympatric R. flagellaris; it is also polymorphic. Rubus ursinus comprises a polyploid spectrum dominated by octoploid and dodecaploid plants. It is an allopolyploid involving phylogenetically distant ancestors with its closest relative being the Hawaiian endemic R. macraei A. Gray. See S. W. Brown (1943) for a discussion of morphological and chromosome number variation in R. ursinus. The widespread, glaucous-stemmed, trifoliate-leaved forms of R. ursinus are vegetatively nearly identical to R. caesius. Of agricultural significance, R. ursinus is a parent of some important cultivars, including loganberry and boysenberry.

There has been uncertainty whether the name Rubus menziesii Hooker and subsequent combinations [Parmena menziesii (Hooker) Greene, R. spectabilis var. menziesii (Hooker) S. Watson, and R. ursinus var. menziesii (Hooker) Focke] pertain to R. spectabilis or R. ursinus. The protologue by Hooker describes a hairy, relatively small, procumbent plant, which is congruent with R. ursinus. The type specimen at Kew also looks like R. ursinus. In the protologue Hooker also claimed the species has red petals and suggested that it may have an affinity with R. spectabilis.

Specimens examined for this study of North American collections attributed to Rubus macrophyllus Weihe & Nees (synonym R. amplificatus Lees) are R. ursinus. If R. macrophyllus was once present in the flora area it is likely absent now; some reports of R. macrophyllus could represent hybrids. There are reports of R. ursinus hybridizing with R. bifrons and R. pensilvanicus in California (T. S. Mallah 1954; L. V. Clark and M. Jasieniuk 2012; L. A. Alice, unpubl.).

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

Rubus nutkanus is distinguished from other flowering raspberries by its erect, unarmed stems, simple leaves, large flowers, white petals, glabrous, clavate styles, and yellowish to reddish stipitate glands covering most plant parts. A hybrid with R. odoratus (R. ×fraseri Rehder) is thought to occur in areas of overlap in northern Michigan (E. G. Voss 1972–1996, vol. 2). Varieties and forms have been described based on indument and glandularity of stems, leaves, petioles, pedicels, and sepals (for example, M. L. Fernald 1950). Different variants often occur mixed in the same population and generally do not correspond to definite geographic regions (N. C. Fassett 1941). Plants from coastal California (considered as var. velutinus) tend to have densely hairy leaf abaxial surfaces; this variation may be environmentally induced; other Rubus species show the same pattern (for example, R. spectabilis var. franciscanus) in that area. Wild thimbleberries are collected in Keweenaw Peninsula, Michigan, and are used in beverages and especially for jam.

Rubus nutkanus is typically associated with western North America but was originally described from plants at its eastern range limit in northern Michigan. The Great Lakes populations are disjunct from western mountain populations by around 600 miles.

The name Rubus parviflorus var. grandiflorus Farwell, which applies here, is illegitimate.

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