Herbs aquatic. Stems usually prostrate-floating, with little or no branching, often rooting at nodes. Leaves: stipules cordate-clasping; petiole 2–7 cm, eglandular; pinnae 2 or 3(or 4) pairs; leaflets 16–40, blades 5–18 mm, without raised-reticulate venation abaxially or veins obscured, margins eciliate or sparsely ciliate. Peduncles 5–20(–30) cm. Spikes 30–50-flowered, ovoid to obovoid; bracts 2(or 3), cordate-clasping, 3–7 × 3–6 mm. Flowers dimorphic, proximal with flattened, petaloid staminodes, distal anther-bearing; calyx 2–4 mm. Legumes 8–10 mm wide, base at right angle to stipe; stipe 4–8 mm, longer than calyx. Seeds 4–8. 2n = 56.

Phenology: Flowering Aug–Oct.
Habitat: Streams, lakes, ponds.
Elevation: 100 m.

Distribution

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Introduced; Ark., South America, s Asia (India), Africa, introduced also in Mexico, West Indies, Central America, elsewhere in Asia.

Discussion

Neptunia oleracea is native to tropical Asia, including India, tropical Africa, and South America and is a cosmopolitan tropical weed. It grows wild and is cultivated as a vegetable throughout southeast Asia, particularly Indochina and Thailand. It is a popular Thai vegetable; the young leaves, shoot tips, and young pods are often used in soup or a spicy and sour salad with seafood. In the United States, Neptunia oleracea is grown as an aquarium or pond plant.

Neptunia oleracea in Arkansas was encountered in a colony on the Little Maumelle River, floating and intermixed with Hydrilla verticillata, near Little Rock (J. H. Peck and B. E. Serviss 2011).

Neptunia natans (Linnaeus f.) Druce (1917), not W. Theobald (1883), pertains here.

Selected References

None.

Lower Taxa

None.