3. Rubus parvifolius L. (Japanese raspberry)
Map 2501
Canes to 300 cm
long, low-arching to prostrate, to 70 cm tall, often rooting at the tips and
occasionally at other nodes. Primocanes green to purplish green in summer,
turning reddish brown in winter, 2.0–3.5 mm in diameter. Prickles moderate to
dense, 0.5–4.0 prickles per cm of cane, slender and downward-angled or
downward-curved, 1–2 mm long. Petioles armed with slender, downward-curved
prickles 1–2 mm long. Stipules 8–18 mm long, linear-lanceolate and sometimes
cleft into 2 lobes. Primocane leaves with 3 leaflets or pinnately compound with
5 leaflets, margins coarsely and broadly toothed, the upper surface glabrous,
the undersurface white-felted. Central primocane leaflets of leaves with only 3
leaflets 3.5–8.5 cm long, 3.0–7.5 cm wide, obovate to broadly subrhombic, often
lobed, angled at the base, angled or tapered to a bluntly pointed tip, the
leaflet stalk about 2/5–1/2 as long as the leaflet blade when only 3 leaflets
are present; lateral leaflets rhombic (or elliptic when 5 leaflets are
present), nearly sessile. Inflorescences simple to complex clusters, in extreme
cases paniculate, 15–45 cm long, with (3–)10–19 flowers and 4–10 leafy bracts,
these mostly with 3 leaflets; flower and inflorescence stalks with stiff hairs,
and small needlelike and broad-based prickles, the flower stalks branched on vigorous
inflorescences. Sepals 6–10 mm long and 3–4 mm wide at flowering, expanding to
8–12 mm long and 4–5 mm wide at fruiting, triangular-ovate. Outer surface of
sepals prickly. Petals 4–6 mm long, spatulate, rose pink. Fruits 10–15 mm long,
10–17 mm wide, hemispheric to short-conic when well formed (some populations
produce few drupelets, if any), bright, glossy red when ripe. 2n=14, 21,
28. May.
Introduced,
known thus far only from Greene County (native to Asia, Australia; naturalized
in Illinois, Iowa, Massachusetts, Missouri, Virginia). Edges of mesic upland
forests; also roadsides and open, disturbed areas.
This unusual
member of subgen. Idaeobatus was first collected by Michael Currier in
1989, but was not correctly determined for another nine years. The species is
first reported from Missouri in the present account. The population, which is
near the Dickerson Park Zoo in Springfield, has continued to expand locally. In
Iowa, populations of this species also have been noted as expanding, and may
invade prairies and savannas (Drobney and Widrlechner, 2010).