Fallopia

1. Plants stout (main stem ca. 8–25 mm thick), erect, with leaves at least 6 cm broad and blades truncate to shallowly cordate at base.

2. Leaf blades cordate or subcordate, usually (at least the larger ones) over 15 cm long, with acute to short-acuminate apex; leaf underside with multicellular hairs along the veins.

F. sachalinensis

2. Leaf blades truncate at the base (often with a small lobe or angled shoulder at each outer angle plus a slight expansion of the blade at summit of the petiole, resulting in a shallowly 3-lobed aspect), mostly less than 15 cm long, abruptly short-acuminate; leaf undersides with the veins merely scabrous-roughened with very short unicellular hairs.

F. japonica

1. Plants with slender stems (up to 3 mm), becoming twining at least in part (young shoots ± erect), with leaves less than 6 (very rarely as much as 9) cm broad and blades deeply cordate with acute to rounded lobes.

3. Nodes mostly with a ring of reflexed bristles; achene smooth and glossy; styles distinctly separate, divergent; outer tepals ± obscurely keeled.

F. cilinodis

3. Nodes glabrous; achene granular or outer tepals definitely keeled or winged; styles virtually absent, the stigmas nearly sessile.

4. Achene with sides granular or cellular in appearance; outer tepals ± papillose or roughened, narrowly keeled (wing less than 0.5 (–0.6) mm broad); fruiting perianth less than 5 (–6) mm long.

F. convolvulus

4. Achene smooth and glossy; outer tepals smooth, ± conspicuously winged (wing over 0.5 mm broad, usually 1 mm); fruiting perianth (6–) 7–10 (–11) mm long (including ± prolonged winged summit of pedicel).

F. scandens

All species found in Fallopia

Fallopia cilinodisFRINGED FALSE BUCKWHEAT 
Fallopia convolvulusBLACK-BINDWEED, FALSE BUCKWHEAT 
Fallopia japonicaJAPANESE KNOTWEED, MEXICAN BAMBOO 
Fallopia sachalinensisGIANT KNOTWEED 
Fallopia scandensFALSE BUCKWHEAT, BLACK-BINDWEED 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. September 19, 2017. http://michiganflora.net/genus.aspx?id=Fallopia.