Isotrema macrophyllum (Lam.) C. Reed (syn.: Aristolochia macrophylla Lam., A. sipho L’Hérit.) (N-Am.) – A very rare, probably more or less naturalized escape from or relic of cultivation. Known from woodland in the surroundings of the castle in Namèche in the valley of river Meuse (Saintenoy-Simon 1999). In 2014 also discovered in Lustin (rocky slope). Possibly overlooked or neglected elsewhere in or near estates. According to Savelsbergh (in Adolphi 1995) also present in Belgium, close the German frontier near Aachen.
In Denée, alongside a disused railway track, another species of Isotrema was observed in 2012. It has leaves and twigs that are conspicuously hairy, whereas I. macrophylla is glabrous. In the absence of flowers it could not yet be identified; it probably belongs to I. tomentosa (Sims) H. Huber or I. manshuriensis (Kom.) H. Huber. It is also illustrated hereunder.
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Selected literature:
Adolphi K. (1983) Eine Verwilderung von Aristolochia macrophylla Lam. bei Walporzheim. Decheniana 136(1): 30.
Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.
Hohla M. (2009) Bromus pumpellianus, Mimulus ringens und Poa bigelovii – neu für Österreich, sowie weitere Beiträge zur Kenntnis der Flora des Innviertels. Beitr. Naturk. Oberösterreichs 19: 151-175.
Meierott L. & Hetzel G. (2017) Aristolochia macrophylla Lam. - bei Würzburg lokal eingebürgert. Ber. Bayer. Bot. Gesell. 87: 219.
Pfeifer H.W. (1962) The status of the name Aristolochia durior Hill. Baileya 10: 5-7.
Saintenoy-Simon J. (1999) Ecotopes du lit majeur de la Meuse wallone. Adoxa 23: 1-12