Yellow water lilies are perennial plants that arise on flexible stalks from rhizomes and large fleshy roots that can resemble bananas. Leaves are oval heart-shape, 3 to 6 inches in diameter, shiny dark green on top and reddish-purple underneath Leaves float on the surface and are seldom emergent. Flowers are large (2 1/2 to 4 inches) bright yellow and usually stand above the water on separate stalks. Yellow water lilies can reproduce from seeds or by spreading of the rhizomes.
http://aquaplant.tamu.edu/database/emergent_plants/yellow_water_lily.htm