Global Range: Most of North America, widespread in other parts of the world except Europe. Sparse.
Distinguished from other water lilies (NUPHAR, NYMPHAEA) by its relatively small, purplish, many pistilled flowers and by its relatively small, truly peltate (with petiole attached to the center of the blade) leaves.
Habitat & Distribution
Flower-Visiting Insects of Watershield in Illinois
(the honeybee collects pollen, while other insects feed on pollen; nectar is not available as a floral reward; the dioecious flowers of Watershield are mostly wind-pollinated; in this study, a shore fly was considered a secondary pollinator of the flowers, while other insects were non-pollinating; observations are from Osborn & Schneider in Texas)
Apidae (Apinae): Apis mellifera cp np
Ephydridae: Notiphila cressoni fp fq icp
Chrysomelidae: Donacia cincticornis fp np; Curculionidae: Perigaster cretura fp np
Life History and Behavior
Molecular Biology and Genetics
Statistics of barcoding coverage: Brasenia schreberi
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
Rounded National Status Rank: NNR - Unranked
Brasenia is a genus belonging to the family Cabombaceae, consisting of one extant species, Brasenia schreberi. It is widely distributed in North America, the West Indies, northern South America (Venezuela, Guyana), eastern Asia (China, Japan, Korea, Primorye), Australia, the Indian Subcontinent, and parts of Africa.
Brasenia is an perennial aquatic plant with floating, peltate leaves and rhizomatous stems. It is identified by its bright green leaves, small purple flowers that bloom from June through September, and a thick mucilage that covers all of the underwater organs, including the underside of the leaves, stems, and developing buds. This mucilage may be an anti-herbivore defence trait, perhaps to deter snail grazing. It grows in shallow water of lakes, rivers and beaver ponds, particularly those with somewhat acidic water.
Brasenia exhibits wind pollination. The flowers have a two-day blooming period. On the first day, the functionally female, or pistillate flower, extends above the surface of the water and exposes the receptive stigmas. The flower then recedes below the water surface and on the following day emerges as a functionally male, or staminate flower. It is elevated higher than on the previous day and the anther-bearing filaments are extended beyond the female carpels. The anthers dehisce, releasing the pollen, and the flower is then withdrawn below the water where the fruit develops.
Brasenia is cultivated as a vegetable in China (where it is known as 莼菜，Pinyin: chún cài) and where it is used in Hangzhou in the well-known local speciality "West Lake Water Shield Soup (西湖莼菜汤)  and in Japan (where it is known as junsai).
The mucilage it produces has been found to have anti-algal and anti-bacterial properties that may be useful as a natural weed control.
Species of Brasenia occurred during the interglacial of Europe, but like many other aquatic plant species and genera, it does not occur there now.
Brasenia schreberi (syn. B. nymphoides, B. peltata) has the common name water-shield (also watershield or water shield).
- Kew World Checklist of Selected Plant Families
- Biota of North America Program, 2013 county distribution map
- Flora of China Vol. 6 Page 119, 莼菜属 chun cai shu, Brasenia Schreber, Gen. Pl. 1: 372. 1789.
- Iwatsuki, K., Boufford, D.E. & Ohba, H. (eds.) (2006). Flora of Japan IIa: 1-550. Kodansha Ltd., Tokyo.
- Hokche, O., Berry, P.E. & Huber, O. (eds.) (2008). Nuevo Catálogo de la Flora Vascular de Venezuela: 1-859. Fundación Instituto Botánico de Venezuela.
- Figueiredo, E. & Smith, G.F. (2008). Plants of Angola. Strelitzia 22: 1-279. National Botanical Institute, Pretoria.
- Acevedo-Rodríguez, P. & Strong, M.T. (2012). Catalogue of seed plants of the West Indies. Smithsonian Contributions to Botany 98: 1-1192.
- Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. Figure 6.9
- Taylor,Mackenzie L. and Jeffrey M. Osborn. 2006. Pollen ontogeny in Brasenia (Cabombaceae, Nymphaeales). American Journal of Botany 93: 344-356
- "Hangzhou Cuisine". Retrieved April 2014.
- Sculthorpe, C. D. 1967. The Biology of Aquatic Vascular Plants. Reprinted 1985 Edward Arnold, by London. p. 404.
- Pringle, James S. Possible eponymy of the generic name Brasenia Schreb. in Sida. vol. 16. no. 3. pp. 597-600. 1995. 
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