Rubus ulmifolius
Rubus pensilvanicus
elm-leaf blackberry
Pennsylvania blackberry, ronce de pennsylvanie
biennial, erect, then arching, usually moderately, rarely sparsely, hairy hairs stellate, eglandular, strongly pruinose;
prickles absent or sparse to dense, erect to hooked, stout, 3–10 mm, broad-based.
biennial, erect to arching, glabrous or sparsely to densely hairy, eglandular or sparsely to moderately, rarely densely, sessile- to short-stipitate-glandular, not pruinose;
prickles sparse to dense, erect or slightly retrorse, stout, 4–10 mm, broad-based.
persistent or nearly so, ternate to palmately compound;
stipules filiform to linear, 4–12 mm;
leaflets 3–5, terminal ovate, elliptic, or suborbiculate to obovate, 4–10 × 2–6(–9) cm, base rounded to cuneate, unlobed, margins finely to moderately serrate, apex acute or acuminate to attenuate, abaxial surfaces with hooked prickles on larger veins, densely white short-velutinous, hairs usually minute, eglandular.
deciduous, palmately compound, not lustrous;
stipules filiform to narrowly lanceolate, (3–)5–15(–20) mm;
leaflets (3–)5(–7), terminal ovate to lanceolate, 5–15 × 3–13 cm, base rounded to shallowly cordate, unlobed, margins finely to coarsely singly or doubly serrate, apex acuminate to long-attenuate, abaxial surfaces green, usually with retrorse prickles on midveins, moderately hairy, eglandular or sparsely to moderately sessile- to short-stipitate-glandular along veins.
terminal, 10–60-flowered, paniculiform or thyrsiform.
terminal on short shoots, usually appearing axillary, (2–)5–12(–16)-flowered, cymiform, racemiform, or thyrsiform.
unarmed or prickles moderate to dense, erect to hooked, densely short-hairy, eglandular.
unarmed or prickles sparse, erect, glabrous or sparsely to densely hairy, eglandular or sparsely to moderately sessile- to short-stipitate-glandular.
bisexual;
petals usually pink, sometimes white, obovate or elliptic to suborbiculate, 5–12 mm;
filaments filiform;
ovaries apically hairy.
bisexual;
petals white, usually obovate to elliptic, rarely suborbiculate, 8–40 mm;
filaments filiform;
ovaries glabrous.
black, globose to ovoid, 1–1.5 cm;
drupelets 10–40, strongly coherent, separating with torus attached.
black, globose to cylindric, 1–2 cm;
drupelets 10–100, strongly coherent, separating with torus attached.
= 14.
= 14, 21, 28, 35, 36, 42.
Rubus ulmifolius
Rubus pensilvanicus
Rubus ulmifolius can be distinguished, especially from the closely related R. bifrons and R. vestitus, by its strongly pruinose stems, finely serrate leaflets, and lack of glands throughout. Unlike R. ulmifolius, strongly pruinose native Rubus species lack relatively large and showy pink petals. Some new stems developing from tip-rooting, and early leaves on such stems (especially in shade), are not whitened abaxially and are tomentose. Such unusual stems develop typical leaves and surfaces in parts formed later.
There has been nomenclatural confusion over unarmed plants of Rubus ulmifolius (see E. Monasterio-Huelin and H. E. Weber 1996). Rubus inermis Willdenow is an illegitimate later homonym of R. inermis Pourret, and the type specimens for both names are of poor-quality. If an unarmed variety of R. ulmifolius is to be recognized, such as occurs in California, the name var. anoplothyrsus Sudre should be used instead of var. inermis (Willdenow) Focke.
Rubus ulmifolius is attractive and is potentially weedy but relatively uncommon, found primarily in coastal California from the San Francisco Bay region southward. It probably no longer persists in New Jersey, last collected there in 1897, and it is rare in Nevada and Oregon. Rubus ulmifolius likely hybridizes with R. bifrons where they co-occur; it is one of relatively few diploid and sexually reproducing species of European blackberries.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
As circumscribed here, Rubus pensilvanicus represents sect. Arguti (L. H. Bailey) L. H. Bailey, in which Bailey (1941–1945) recognized 109 species.
More strongly glandular plants of Rubus pensilvanicus may represent introgression with R. allegheniensis or other species, especially when exhibiting long-stipitate glands. Thyrsiform inflorescences are present in plants that have been called R. missouricus. There are reports (T. S. Mallah 1954; L. V. Clark and M. Jasieniuk 2012; B. Sutherland and L. A. Alice, unpubl.) of R. pensilvanicus hybridizing with R. ursinus.
Rubus pensilvanicus is introduced in California, Idaho, and Washington.
The following nothospecies names are based on putative hybrids involving Rubus pensilvanicus and: R. allegheniensis (R. ×avipes L. H. Bailey, R. ×floricomus Blanchard, R. ×orarius Blanchard); R. canadensis (R. ×amabilis Blanchard [not Focke], R. ×amicalis Blanchard, R. ×elegantulus Blanchard [=R. canadensis var. elegantulus (Blanchard) Farwell], R. ×multilicius L. H. Bailey, R. ×noveboracus L. H. Bailey, R. ×pergratus Blanchard [= R. canadensis var. pergratus (Blanchard) L. H. Bailey], R. ×crux Ashe); R. cuneifolius (R. ×acer L. H. Bailey, R. ×acer var. subacer L. H. Bailey, R. ×argutinus L. H. Bailey, R. ×floridensis L. H. Bailey); R. flagellaris (R. ×akermanii Fernald, R. ×darlingtonii L. H. Bailey, R. ×dissitiflorus Fernald, R. ×hypolasius Fernald, R. ×janssonii L. H. Bailey, R. ×largus L. H. Bailey, R. ×recurvicaulis Blanchard, R. rossbergianus Blanchard); R. setosus (R. ×wisconsinensis L. H. Bailey).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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