Mazus pumilus

Mazus pumilus (Burm.f.) Steenis (syn.: M. japonicus (Thunb.) Kuntze) (S and SE-As.) – An exceptional alien. Sometimes seen as a bonsai-weed in garden centers in Belgium. In 2014 observed for the first time in the wild: several plants grew on the gravelly banks of river Maas in the Negenoord-Kerkeweerd nature reserve (Lanaken) and its presence there was confirmed in 2015 and 2016. The origin of these plants remains obscure. Mazus pumilus had been recorded before in similar circumstances in the surroundings of Pavia in Italy (Gardini 1985, Desfayes 1997). More recently, still in Italy, it has also been observed as a pavement weed in the city of Verona (see: http://www.actaplantarum.org/floraitaliae/viewtopic.php?f=40&t=48519&sid=4164601c9356baa4f3a0cf1bc1d1b535). In similar circumstances it is also know from Frankurt in Germany since 2013 (Walther 2014), France (Brousseau 2017), etc.

The plants from Lanaken were initially ascribed to Lindernia spec. (L. dubia being known from the same area). The latter is readily distinguished by its smaller calyx ca. 3 mm with narrow lobes (c. 0.5 mm wide) that are free to base (vs. calyx campanulate, 3-8 mm, with ovate-triangular lobes almost as long as tube) and a slightly smaller corolla (c. 6.5 mm vs. 10 mm). Both these species may have been confused elsewhere in Europe.

Mazus pumilus itself is a very variable species (see Hong & al. 1998). The not enlarged calyx, not entire leaves and pedicel length (5-12 mm) suggest our plants to belong to var. pumilus.

 

Selected literature:


Bacigalupo N.M. (1991) Mazus japonicus (Scrophulariaceae), adventicia en la Argentina. Bol. Soc. Argent. Bot. 27(1-2): 131-132.

Brousseau C. (2017) Le scoop botanique de la saison: une plante exotique inconnue en France découverte en Ariège. Association des Naturalistes de l'Ariege. Bulletin 88: 4.

Desfayes M. (1997) Mazus pumilus (Scrophulariaceae), adventice nouvelle pour l’Italie, et Lemna minuta (Lemnaceae) espèce nouvelle pour la province de Pavie. Saussurea 28: 65-66.

Gardini S.P. (1985) Mazus japonicus (Thunb.) Kuntze in Italia. Atti Ist. Bot. Univ. Pavia 2 serie 7: 95-98.

Hong D., Yang H., Jin C., Fischer M.A., Holmgren N.H. & Mill R.R. (1998) Scrophulariaceae. In: Wu Z.Y. & P.H. Raven (eds.), Flora of China, vol. 18. Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis: 1-212. [available online at: http://flora.huh.harvard.edu/china/PDF/PDF18/mazus.pdf]

Reddy C.S. & Raju V.S. (2000) On the occurrence of Mazus pumilis (Burm. f.) Steenis (Scrophulariaceae) in Kerala, India. J. Econ. Taxon. Bot. 24(2): 319.

Walther F. (2014) Fundmeldungen. Neufunde - Bestätigungen - Verluste. 27/269 Mazus pumilus. Botanik und Naturschutz in Hessen 27: 120. [available online at: http://www.bvnh.de/bnh/]

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith