Mazus Lour.
As currently understood, Mazus is a genus with ca. 20-35 species in eastern Asia, New Zealand and Australia (Mabberley 2008). It is most diverse in China where most of the species occur (Hong & al. 1998). Several species are economically important: five stoloniferous perennials are cultivated as carpeting ornamentals in Europe (Mill 2000; Jäger & al. 2008). Out of these, at least M. miquelii Makino has been recorded as an escape, for instance in the Lombardia region in Italy (comm. G. Galasso). An additional species, the annual Mazus pumilus (Burm.f.) Steenis, is a common weed throughout the (sub-) tropics and has been recorded lately in Belgium as well.
1 Annual, stolons absent. Corolla 7-9 mm === Mazus pumilus
1 Stoloniferous perennial. Corolla 13-22 mm === M. reptans
Literature:
Barker M.R. (1991) A taxonomic revision of Mazus Lour. (Scrophulariaceae) in Australasia. In: Banks M.R. & al. (eds.), Aspects of Tasmanian Botany: a tribute to Winifred Curtis. Hobart, Tasmania, Royal Society of Tasmania: 85-94. [available online at: http://eprints.utas.edu.au/14668/1/Barker_A_toxonomic_revision.pdf]
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]
Hsieh T.H. (2000) Revision of Mazus Lour. (Scrophulariaceae) in Taiwan. Taiwania 45(2): 131-146. [available online at: http://tai2.ntu.edu.tw/Taiwania/pdf/tai.2000.45.2.131.pdf]
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Li H.L. (1954) The genus Mazus. Brittonia 8: 29-38.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Mill R.R. (2000) Mazus. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 280-282.
Rabeler R.K. & Freeman C.C. (2013) Mazaceae. Flora of North America, Provisional Publication. Flora of North America Association. February 15, 2013. [available online at: http://floranorthamerica.org/files/Mazaceae03f%20SI%20CH%20for%20web.pdf]