Neptunia oleracea, commonly known in English as water mimosa or sensitive neptunia, is pantropical nitrogen-fixing perennial legume. Genus and common name come from Neptune, god of the sea, in reference to the aquatic habit of some species in the genus.Aerenchyma (white spongy air-conducting tissue that gives stems buoyancy) forms on stems floating in water, but does not form on stems growing on land. Plants typically grow to as much as 6" tall, but stems will spread in the water to 3-5' long. Stems are clad with bi-pinnate, fine, mimosa-like sensitive leaves that close up when touched. Primary leaf segments have 8-40 small oblong leaflets arranged in opposite pairs. Tiny greenish-yellow flowers are densely crowded into feathery orbicular inflorescences that bloom in summer. Fruits are flat pods (to 1-2" long). Floating aquatic plant stems often form thick foliage mats and is considered to be an invasive aquatic weed in some tropical waters where large mats may form that choke waterways, resulting in restricted water flow, reduced water quality, reduced fish activity and loss of some underwater and native wetland plants.
