Water caltrop

Family: Lythraceae
Scientific name: Trapa natans
Description: Plant Form: Mat forming aquatic herb. Size: Can reach 4.5 m deep. Stem: Submerged. Leaves: Submerged leaves feather like in whorls around stem. Surface leaves 2-3 cm long in rosette in oval, triangle or rectangle shape with saw-toothed edges. Flowers: White with 4 petals, above surface. Fruit and Seeds: Hard, woody or bony nut, 3 cm wide with sharp spines. Habitat: Dams, ponds and lakes.

Example images for this weed