Ludwigia

Ludwigia L.

Ludwigia is a nearly cosmopolitan genus of 82 species. It is most diverse in tropical and subtropical regions, especially in the New World but also in Africa. One species is native in Belgium (Ludwigia palustris (L.) S. Elliott) (Verloove & Lambinon 2012). Hoch (1997) cites 10 species that are cultivated as ornamentals in Europe (mainly as aquatics and/or aquarium plants) but only few are more or less widespread in cultivation (most are frost-sensitive in large parts of Europe). Ludwigia also counts some aggressive environmental weeds, including some that are commonly cultivated as ornamentals (see below). More information on the invasive behaviour of two species in Belgium is found here: http://www.fsagx.ac.be/ec/gestioninvasives/Documents/Fiche%E9cologiqueLudwigiasppbis.pdf.

Ludwigia section Dantia (DC.) Munz (to which native L. palustris belongs) contains several weedy (semi-) aquatic species, some of which are cultivated as aquarium plants. Some of these are very reminiscent of Ludwigia palustris and might pass unrecorded. Unexpected records (outside its known native distribution range or in man-made habitats) of vigorous plants of the latter are suspect and might refer to Ludwigia xkentiana E.J. Clement (syn.: L. muellertii hort.; a putative hybrid of L. repens and L. palustris) (see Clement 1997, 2000) or L. repens J.R. Forst. (syn.: L. natans Elliott; see Garve & van der Meijden 1997) (see also Peng & al. (2005). Especially Ludwigia xkentiana (binomial remarkably overlooked by Peng & al. 2005) is very similar to L. palustris. Petalous (but then tiny petals readily deciduous) as well as apetalous plants occur and they are often sterile although up to 35% may prove to be fertile (Peng & al. 2005).


1       Leaves opposite. Stamens as many as sepals (always 4). Capsule 1,5-5 mm long, stalkless. Petals absent (native) === Ludwigia palustris

         Leaves alternate. Stamens twice as many as sepals (10 or 12). Capsule 15-40 mm long, stalks 6-90 mm long. Petals bright yellow, very showy, 7-31 mm long === 3

2       Sepals (persistent on the capsule) 10-19 mm long after anthesis. Leaves of flowering stems lanceolate, ca. 5x as long as wide, the longer usually exceeding 60 mm. Longer hairs on flowering stems up to 2 mm long. Petals up to 31 mm long === Ludwigia hexapetala

         Sepals (persistent on the capsule) 3-10 mm long after anthesis. Leaves of flowering stems obovate to nearly circular, ca. 2-3x as long as wide, the longer usually less than 60 mm long. Longer hairs on flowering stems up to 1 mm long. Petals up to 17 mm long === L. peploides


Literature:

Clement E.J. (1997) Ludwigia x muellertii Hort. new to Britain. BSBI News 77: 54.

Clement E.J. (2000) Ludwigia x kentiana E.J. Clement: a new hybrid aquatic. Watsonia 23(1): 167-172.

Dandelot S., Verlaque R., Dutartre A. & Cazaubon A. (2005) Ecological, dynamic and taxonomic problems due to Ludwigia (Onagraceae) in France. Hydrobiologia 551: 1-6.

Delay J. & Petit D. (2008) Les espèces aquatiques invasives du Nord de la France et leur biologie. Bull. Soc. Bot. N. Fr. 61(1-4): 5-22.

Duvigneaud J., Saintenoy-Simon J. & Delmarche C. (1996) Un complément à apporter à la Nouvelle Flore de la Belgique et des Régions voisines: le traitement du genre Ludwigia. Adoxa 10: 9-10.

Garve E. & van der Meijden R. (1997) Ludwigia natans Elliott bei Hannover sowie Hinweisse zur Bestimmung adventiver Ludwigia-Arten. Flor. Rundbr. 31(1): 9-12.

Hoch P.C. (1997) Ludwigia. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 347-348.

Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.

Peng C.I., Schmidt C.L.., Hoch P.C. & Raven P.H. (2005) Systematics and evolution of Ludwigia section Dantia (Onagraceae). Ann. Missouri Bot. Gard. 92: 307-359.

Raven P.H. (1963) The Old World species of Ludwigia (including Jussiaea), with a synopsis of the genus (Onagraceae). Reinwardtia 6(4): 327-427.

Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.

Van Moorsel R. & Odé B. (2002) Vergeet-mij-nietjes. Waterlepeltjes. Gorteria 28(5): 119-122.

Wagner W.L., Hoch P.C. & Raven P.H. (2007) Revised classification of the Onagraceae. Syst. Bot. Monogr. 83: 1-240.

Zardini E. & Raven P.H. (1992) A new section of Ludwigia (Onagraceae) with a key to the sections of the genus. Syst. Bot. 17(3): 481-485.



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