Fallopia scandens
Fallopia ×bohemica
climbing bindweed, climbing false-buckwheat
Bohemian knotweed, hybrid Japanese knotweed, hybrid knotweed
ocrea usually deciduous, tan or brown, cylindric to funnelform, 1–6 mm, margins oblique, face not fringed with reflexed hairs and slender bristles at base, otherwise glabrous or scabrid;
petiole 0.5–10 cm, glabrous or scabrid in lines;
blade cordate, truncate-deltate, or hastate, 2–14 × 2–7 cm, base cordate, margins wavy, scabrid, apex acuminate, abaxially and adaxially faces glabrous or papillose to scabrid, not glaucous, the abaxial rarely minutely dotted.
ocrea usually deciduous, brownish, cylindric, 4–6(–10) mm, margins oblique, face without reflexed hairs and slender bristles at base, otherwise glabrous or minutely puberulent;
petiole 1–3 cm, glabrous;
blade ovate, 5–25(–30) × 2–10 cm, base truncate to cordate, margins entire, glabrous or scabrous to ciliate, apex cuspidate, abaxial face minutely dotted, glaucous, with hairs along veins unicellular or appearing so, obscure, shorter than 0.1 mm, tips acute, adaxial face glabrous.
axillary, erect or spreading, racemelike, 1–28 cm, axes scabrid;
peduncle 0.1–7 cm or absent, scabrid.
terminal and axillary, erect or spreading, paniclelike or sometimes racemelike, 4–12 cm, axes puberulent;
peduncle 0.1–3.5 cm or absent, puberulent.
ascending or spreading to reflexed, articulated distally, 4–8 mm, glabrous.
ascending or spreading, articulated proximal to middle, 3–5 mm, glabrous.
bisexual, 3–6 per ocreate fascicle;
perianth accrescent in fruit, green to white or pinkish, 3.8–8 mm including stipelike base, glabrous;
tepals elliptic to obovate, apex obtuse to acute, outer 3 winged;
stamens 8;
filaments flattened proximally, pubescent proximally;
styles connate;
stigmas capitate.
bisexual or pistillate, 3–8(–15) per ocreate fascicle;
perianth accrescent in fruit, white or greenish white to pink, 4–6 mm including stipelike base, glabrous;
tepals obovate to elliptic, apex obtuse to acute, outer 3 winged;
stamens 8;
filaments flattened proximally, glabrous;
styles connate basally;
stigmas fimbriate.
included, dark brown to black, 2–6 × 1.4–3.5 mm, shiny, smooth; fruiting perianth glabrous, wings undulate or crinkled, rarely flat, (0.7–)1.5–2.1 mm wide, decurrent on stipelike base nearly to articulation, margins wavy-crenate to incised or lacerate, rarely entire.
included, dark brown, 2.6–3.2 × 1.4–1.8 mm, shiny, smooth; fruiting perianth glabrous, wings flat to undulate, 1.5–2.1 mm wide at maturity, decurrent on stipelike base nearly to articulation, margins entire.
= 20.
= 44, 66, 88 (Korea).
Fallopia scandens
Fallopia ×bohemica
Fallopia scandens has a complex nomenclatural history, which in North America usually involves three taxonomic elements: F. scandens and F. cristata, both native in North America, and F. dumetorum, which is native in Europe. Achene and perianth characters have been used to distinguish these elements, but variable and intergrading morphologies have caused taxonomists to combine them variously. Morphometric (S. T. Kim et al. 2000) and flavonoid (M. H. Kim et al. 2000) studies suggest that F. scandens and F. dumetorum are distinct species. Where F. scandens is absent, European specimens of F. dumetorum are distinctive. This distinction is far less clear in North America, where both species occur. Experience suggests that many North American herbarium specimens attributed to F. dumetorum are misidentified.
Fallopia cristata has been distinguished from F. scandens and F. dumetorum by its smaller fruiting perianths (5–7[–9] mm) bearing narrower (1.2–1.7 mm wide), undulate-crenate or lacerate wings, and smaller achenes (2.1–2.7 mm). Extreme forms are easily identified; some specimens grade gradually into F. scandens, making recognition of F. cristata of questionable utility. S. T. Kim et al. (2000) used morphometric studies as a basis for recommending that F. cristata is best treated as a variety of F. scandens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Fallopia ×bohemica is a widespread hybrid between F. japonica and F. sachalinensis. It went unnoticed in the North American flora until recently (P. F. Zika and A. L. Jacobson 2003). It exhibits morphological intermediacy with its parents and is distinguished most reliably by the pubescence along the veins on the abaxial surface of leaves produced early in the growing season. Hairs of F. sachalinensis are multicellular, usually twisted, acute to acuminate at the tip, and 0.2–0.6 mm; those of F. japonica are unicellular, blunt, and barely raised, making the veins appear scabrous. Fallopia ×bohemica has hairs that are unicellular or appearing so (actually often obscurely multicelluar), acute at the tip, and shorter than 0.1 mm. The hairs are easiest to find on fresh leaves; older leaves often are glabrescent and diagnostic hairs are hard to find. Hybrid specimens are most often misidentified as F. japonica.
Like its parents, Fallopia ×bohemica is gynodioecious. J. P. Bailey et al. (1996) reported it to be partially to fully fertile. In North America, reproduction appears to be largely vegetative by rhizomes.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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