Sagittaria is a relatively small genus of ca. 35 species. A large majority is native in North America. One species is native in Belgium, Sagittaria sagittifolia L. (Lambinon & al. 2004). A second species, Sagittaria latifolia, is recently becoming naturalised.
In addition to the species treated below several others are in cultivation in Europe. King (1986) enumerates seven species most of which have been reported as escapes in Europe. The more recent account of Sagittaria in Jäger & al. (2008) furthermore cites S. platyphylla (Engelm.) J.G. Smith and S. engelmanniana J.G. Smith as Central European ornamentals. Sagittaria subulata (L.) Buchen. is naturalised in Berlin (Germany) and the British Isles (Mühlberg 2000, Clement & Foster 1994, Sell & Murrell 1996) and S. graminea Michaux in France and in the British Isles (Vivant 1980, Clement & Foster 1994, Sell & Murrell 1996). Both could occur as escapes in Belgium as well. Finally, Sagittaria rigida Pursh and S. montevidensis Chamisso et Schlecht. have been reported as rare escapes elsewhere in Europe.
- Petals entirely white, up to 20 mm long. Anthers yellow. Achenes 2,5-4 mm with subapical beak > 1 mm. Mature (emergent) leaves usually broadly ovate-triangular, obtuse at apex === Sagittaria latifolia
- Petals at least basally suffused with purple, usually less than 15 mm long. Anthers reddish-purple. Achenes 4-6 mm with subapical beak < 1 mm. Mature (emergent) leaves very variable but never broadly obtuse at apex (native) === S. sagittifolia
Additional aliens: Sagittaria graminea Michaux (N-Am.) has been included in the Flora of Belgium (Lambinon & al. 2004) but there seems to be no reliable source. It should be removed in a future edition of the Flora.
Literature
Bogin C. (1955) Revision of the genus Sagittaria (Alismataceae). Mem. New York Bot. Gard. 9: 179-233.
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Ford K.A. & Champion P.D. (2020) Sagittaria. In: Flora of New Zealand, fascicule 7: 34 pp. Available online at: http://www.nzflora.info/pdfs/FloraOfNewZealand-SeedPlants-7-FordChampion...
Haynes R.R. & Hellquist C.B. (2000) Alismataceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 22. Oxford University Press, New York-Oxford: 7-25.
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.
King C.J. (1986) Sagittaria. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1. Cambridge University Press, Cambridge: 111-112.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Mühlberg H. (2000) Sagittaria subulata im Stadtgebiet von Berlin. Schlechtendalia 5: 27-30.
Rataj K. (1972a) Revision of the genus Sagittaria. Part I (Old World species). Annot. Zool. Bot. 76: 1-31.
Rataj K. (1972b) Revision of the genus Sagittaria. Part II (The species of West Indies, Central and South America). Annot. Zool. Bot. 78: 1-61.
Sell P.D. & Murrell G. (1996) Flora of Great Britain and Ireland. Vol. 5. Cambridge University Press, Cambridge: 410 p.
Stace C. (1997) New flora of the British Isles, 2nd ed.: XXVII + 1130 p. Cambridge University Press.
Vivant J. (1980) Phanérogames adventices se naturalisant dans les Landes et les Pyrénées-Atlantiques. Bull. Soc. Bot. Fr. 127: 289-295.