Rubus trivialis
Rubus caesius
southern dewberry
European dewberry
biennial, initially low-arching, then falling and creeping (or climbing through other vegetation), glabrous or moderately hairy, sparsely to densely short- to long-stipitate-glandular, not pruinose;
prickles moderate to dense, recurved, sometimes distally slender, 1–4 mm, broad-based;
bristles absent or sparse to dense, erect to retrorse, red to purple, rarely green, slender, weak, gland-tipped.
biennial, creeping or arching then creeping, glabrous or hairy, eglandular or sparsely sessile- to short-stipitate-glandular, strongly pruinose;
prickles sparse to dense, erect to retrorse, slender, 1–3 mm, narrow- or broad-based.
persistent or semipersistent, ternate to palmately compound, lustrous;
stipules filiform, linear, or lanceolate, 2–12(–15) mm;
leaflets 3–5, terminal narrowly elliptic or ovate to obovate, 2–8.5 × 0.7–4.5 cm, base rounded to cuneate, unlobed, margins moderately to coarsely serrate to doubly serrate, apex acute to acuminate, abaxial surfaces with hooked prickles on midvein, glabrous or sparsely to moderately hairy, eglandular or sparsely short-stipitate-glandular along central vein.
deciduous, ternate;
stipules linear-lanceolate to ovate, 5–15 mm;
terminal leaflets ovate, 4–14 × 3–10 cm, base rounded to shallowly cordate, unlobed or shallowly lobed, margins coarsely serrate to doubly serrate, apex acute to acuminate, abaxial surfaces with prickles on midveins or unarmed, sparsely to moderately hairy, eglandular or sparsely short-stipitate-glandular along larger veins.
terminal on short shoots, usually appearing axillary, 1(–3)-flowered.
terminal on short shoot, usually appearing axillary, 1–6-flowered, solitary flowers, cymiform, or racemiform.
prickles and, often, bristles moderate to dense, recurved, moderately to densely hairy, sparsely to moderately sessile- to short-stipitate-glandular.
unarmed or prickles sparse to dense, erect to retrorse, densely hairy, sparsely to densely sessile- to short- or long-stipitate-glandular.
bisexual;
petals white to pink, elliptic to obovate, 10–16(–25) mm;
filaments filiform;
ovaries glabrous.
bisexual;
petals white, obovate to elliptic or suborbiculate, 7–13 mm;
filaments filiform;
ovaries glabrous.
black, globose to ovoid, 1–1.5(–2) cm;
drupelets 10–50, strongly coherent, separating with torus attached.
appearing bluish, black beneath bloom, pruinose, globose, 0.5–1.5 cm;
drupelets 1–5(–20), weakly coherent, separating with torus attached.
= 14.
= 28.
Rubus trivialis
Rubus caesius
Rubus trivialis is distinguished from other species of Rubus by its frequently glandular-bristly and generally creeping stems, abundant recurved prickles, and typically persistent or semipersistent, lustrous primocane leaves with relatively narrow leaflets. Although emerging primocanes typically reach to 30 cm above the ground, vigorous plants can have new primocanes standing erect to 70 cm that later fall to the ground or onto adjacent vegetation as they continue to enlarge. L. H. Bailey (1941–1945) believed that there was no clear separation between members of sect. Persistentes Fernald (referred to by Bailey as sect. Verotriviales [illegitimate sectional name for R. trivialis and associated species]) and sect. Procumbentes (by Bailey as sect. Flagellares; including R. flagellaris and related species). All characteristics that he recognized for distinguishing sect. Persistentes from sect. Procumbentes are often present in the latter, with the exception of hispid-setose stems, and glabrous plants of R. trivialis are difficult to distinguish from some plants of R. flagellaris; to include the latter species within the former would be reasonable.
Rubus ×inferior L. H. Bailey is a putative hybrid of R. trivialis and R. cuneifolius.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Within the flora area, Rubus caesius usually produces fruit with few, relatively large drupelets; in Eurasia, fruit with more drupelets are typical, and weakly pruinose fruit have been observed.
Rubus caesius is vegetatively similar to R. flagellaris and is introduced into parts of the geographic range of the latter; see M. P. Widrlechner (1998) for a comparison of these two species. Rubus caesius shows striking vegetative similarity to pruinose, trifoliate-leaved plants of R. ursinus, with which it may have a close relationship (L. A. Alice, unpubl.). In the absence of flowers or fruit, these two species could be mistaken for one another. Rubus caesius generally has broader middle primocane leaflets than R. ursinus, but that is not a consistent difference. Rubus caesius may have been introduced into the geographic range of R. ursinus; most herbarium specimens surveyed have been inadequate to make a proper determination. On specimen labels, herbarium collectors should describe at least the color of the fruit. In the last decade, R. caesius apparently has become much more aggressive around Ithaca, New York, despite occurring there since the early twentieth century (F. R. Wesley, pers. comm.).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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