Wolffia columbiana

Wolffia columbiana Karsten (Am.) – A very rare but probably overlooked alien. Discovered in a pond in nature reserve Stamprooierbroek in Kinrooi in 2017 (Hendrickx & Verloove 2019). In 2018 also found in Uitkerkse Polder and in Keerbergen (comm. D. De Beer).
This species much resembles native W. arrhiza but its fronds are paler, mostly translucent and with much less stomata. Fronds lie almost on the water, rather than being submersed.
W. columbiana is known in Europe from Germany, the Netherlands and Italy (Achterkamp & Soes 2014, Schmitz & al. 2014, Ardenghi & al. 2017) but it is probably widely overlooked elsewhere.

Selected literature:

Achterkamp B. & Soes M. (2014) Twee nieuwe soorten Wolffia voor Nederland. Floronia – Nieuwsbrief van de Floron districten D9 & 22 Gelderland-West en –Midden: 21-23. [available online at: http://www.floron.nl/Portals/1/Plaatjes/Districten/D22_Floronia_najaar_2...

Armstrong W.P. (1982) Duckweeds, California's smallest wildflowers. Fremontia 10(3): 16-22.

Ardenghi N.M.G., Armstrong W.P. & Paganelli D. (2017) Wolffia columbiana (Araceae, Lemnoideae): first record of the smallest alien flowering plant in southern Europe and Italy. Botany Letters 164(2). [available online at: http://www.tandfonline.com/doi/pdf/10.1080/23818107.2017.1319293?needAcc...

Cody W.J. (1980) Wolffia columbiana (Lemnaceae), water meal, new to Manitoba. Canad. Field Nat. 94(2): 193-194.

Hendrickx P. & Verloove F. (2019) Wolffia columbiana nu ook waargenomen in België. Dumortiera 114: 8-12. [avaible online at: http://db.plantentuinmeise.be/DUMORTIERA/DUM_114/Dum_114_8-12_Wolffia_co...

Schmitz U., Köhler S. & Hussner A. (2014) First records of American Wolffia columbiana in Europe – Clandestine replacement of native Wolffia arrhiza? BioInvasions Records 3: 213-216. [available online at: http://www.reabic.net/journals/bir/2014/4/BIR_2014_Schmitz_Hussner.pdf]  

Schmitz U., Köhler S. & Nesemann H. (2016) Neue Nachweise der Kolumbianischen Zwergwasserlinse Wolffia columbiana in Europa – Bei wie vielen vermeintlichen Vorkommen von Wolffia arrhiza handelt es sich in Wirklichkeit um den Neophyten? Veröff. Bochumer Bot. Ver. 8(1): 1-10. [available online at: https://www.botanik-bochum.de/publ/OVBBV8_1_Schmitz_Koehler_Nesemann_Wol...

White S. & Wise R. (1998) Anatomy and ultrastructure of Wolffia columbiana and Wolffia borealis, two nonvascular aquatic angiosperms. International Journal of Plant Science 159(2): 297-304.

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