Fallopia Adans.
(incl. Bilderdykia Dum., excl. Reynoutria Houtt.)
Fallopia, as currently understood (see Galasso & al. 2009), comprises about 15 species that are native in parts of the Americas, Asia, Europe and Africa. The generic limits of Fallopia and Reynoutria have long been controversial. Haraldson (1978) recognised both as distinct genera and recent molecular research has confirmed their autonomy (Galasso & al. l.c.). On the other hand, hybridisation often occurs between representatives of both genera (for instance between Fallopia baldschuanica and Reynoutria japonica; xReyllopia conollyana (J.P. Bailey) Galasso – see Bailey 1988, 2001), which confirms their close affinity.
Two species, Fallopia convolvulus (L.) Á. Löve and F. dumetorum (L.) Holub are more or less widespread natives in Belgium.
All non-native representatives of the genera Fallopia and Reynoutria in Belgium are undesirable invaders. Fallopia baldschuanica, for instance, is becoming a nuisance in coastal dunes.
- Perennial, woody at base. Inflorescence panicle-like. Stigmas peltate. Stem 5-15 m long === 1. Fallopia baldschuanica
- Slender annual. Flowers predominantly in axillary clusters. Stigmas capitate. Stem 10-200 cm long (native) === F. convolvulus, F. dumetorum
Literature:
Anjen L. & Park C.W. (2003a) Fallopia. In: Wu Z.Y. & al. (eds.), Flora of China, vol. 5. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 315-318.
Bailey J.P. (1988) Putative Reynoutria japonica Houtt. x Fallopia baldschuanica (Regel) Holub hybrids discovered in Britain. Watsonia 17(2): 163-164.
Bailey J.P. (2001) Fallopia x conollyana. The Railway-yard Knotweed. Watsonia 23(4): 539-541.
Galasso G., Banfi E., De Mattia F., Grassi F., Sgorbati S. & Labra M. (2009) Molecular phylogeny of Polygonum L. s.l. (Polygonoideae, Polygonaceae), focusing on European taxa: preliminary results and systematic considerations based on rbcL plastidial sequence data. Atti Soc. It. Sci. Nat. Museo Civ. Stor. Nat. Milano 150(1): 113-148.
Haraldson K. (1978) Anatomy and taxonomy in Polygonaceae subfam. Polygonoideae Meisn. emend. Jaretzky. Symb. Bot. Upsal. 22: 1-93.
Lousley J.E. & Kent D.H. (1981) Docks and knotweeds of the British Isles (BSBI Handbook n° 3). BSBI, London: 205 p.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.