Neptunia oleracea Loureiro
Family
Leguminosae
Synonyms
Neptunia prostrata (Lamk) Baillon, Neptunia natans (L.f.) Druce.
Vernacular Names
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Malaysia |
Keman air, keman gajah, tangki. |
|
English |
Water mimosa. |
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Indonesia |
Kemon (Lampung). |
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Cambodia |
Kânhchhnaèt. |
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Laos |
(‘phak) kas’ééd. |
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Thailand |
Phakkrachet (Central), phakchit (Peninsular). |
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Vietnam |
Rau nh[us]t (South), rau r[us]t (North). |
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French |
Neptunie potagère. |
Geographical Distributions
Neptunia oleracea is widely distributed in the tropics of both hemispheres. The origin of the species is uncertain. It occurs wild and cultivated as a vegetable throughout Southeast Asia, particularly in Thailand and Indo-China.
Description
Neptunia oleracea is a perennial herb which is sometimes grown as an annual, aquatic, floating or prostrate near water’s edge. Its taproot is thick and becomes woody. The stems are terete, measure up to 1.5 m long, rarely branched, become detached from the primary root system, form spongy-fibrous swollen internodes (to float) and produce fibrous adventitious roots at the nodes when growing in water.
The leaves are arranged alternate, bipinnate and with 2-3(-4) pairs of pinnae. The petiole is 2-7 cm long and angled. The rachis is 3.5-8 cm long and angled. The rachis of pinnae is 2.5-6.5 cm long and winged. There are 8-20 pairs of leaflets per pinna which are oblong, measuring 5-18 mm x 1.5-3.5 mm, asymmetrical, hairless or with sparsely ciliate margins.
The inflorescence is an axillary, erect or slightly nodding solitary spike which is obovoid in bud and 30-50-flowered. The peduncle is 5-30 cm long. The flowers are small, sessile and yellow, with the lower ones sterile while the upper ones are bisexual. The bisexual flowers are with bell-shaped sepal of 2-3 mm and 5-lobed. The 5 regular petals are free and 3-4.5 mm long. The 10 free stamens are 6-9 mm long. The pistil is up to 9 mm long and usually exserted beyond the stamens.
The fruit is a legume, broadly oblongoid and flat, measuring 2-3 cm x 1 cm and dehiscent along both sutures. The fruit stalk is longer than the persistent sepal.
There are 4-8 seeds which are ovoid compressed, measuring 4-5 mm x 2.5-3.5 mm and brown.
Ecology / Cultivation
Neptunia oleracea is a common floating plant in and around fresh water ponds, swamps and canals at low altitudes up to 300 m. When the water level falls, the plants perish. The rooted land form has smaller leaves and flowers, and has no spongy floating tissue. The plant prefers 30-80 cm depth of slow-moving water, full sun and hot and humid conditions. Shade, brackish water and saline soil adversely affect plant growth.
Line Drawing / Photograph
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References
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Plant Resources of South-East Asia No.8: Vegetables.
