Trapa natans Linnaeus, 1753
Synonyms: Trapa longicarpa Jank., 1961
Common names: Bulg: Voden orekh, Julyun; Russ: Vodyanoy orekh plavayushchiy; Ukr: Vodyany gorikh plavayuchy
Taxonomic descriptions: Annual water herb. Submarine stem is 40-150 cm length. Leaves 3-4 cm length, 3-4.5 cm width, floating, wide diamond-shaped, from below with hairs along veins. Petioles are 3-10 cm length, cylindrical or with oblong swellings near leaf blades. Fruits (diameter 6-10 mm) with firm cover, four-corned.
World level: VU
Black Sea Regional level: VU
Subregion level: VU
Habitats type, Critical habitats, Limiting factors: Geographic area of species covers both Europe and Mediterranean. The species grows in stagnant or slightly flowing waters 50-250 cm mostly in river valleys, in silt soils. Occurs in pure growth or with other water plants.
Biology: Probably, the species has obligate self-fertilization: there is no data about cross fertilization. Fruits are distributed by flowing waters, mammals and birds. Seeds have a good germination power (up to 40-50 years), annually only a part of them shoot. Flowering during VI-VII. Fruit-bearing - VIII-IX. Reproduction only by seeds.
Population trends: Populations are numerous, particularly in the “Dunajskiye plavni” reserve (Ukraine).
Threats: Drying of wetlands, chemical pollution, output for animal feeding.
Conservation measures taken: The species has been entered in the Red Data Books of Ukraine (1996) and Bulgaria (1984), protected in the Danube delta (Ukraine and Romania).
Conservation measures proposed: To create new protected zones.
Compiled by: S.Dyatlov, M. Filipova, T.Vasilieva