Lumanaja fluviatilis Blanco

A gregarious shrub or small, crooked and twisted tree, 1-4 m tall, up to 10 cm in stem diameter, forming a woody, deep and extensive root system. Branches smooth to slightly grooved. Leaves alternate, simple; stipules keel-like, enlarged at base, 5-6 mm long, caducous; petiole 5-15 mm long, pubescent; blade narrowly lanceolate to oblong, 4-20 cm x 1-2.5 cm, obtuse or rounded at base, acuminate, obtuse or mucronate at apex, bright green, penninerved, thin, chartaceous, upper surface shiny, glabrous, lower surface pubescent, closely glabrescent and minutely lepidote, margin entire or dentate. Male inflorescence an axillary, densely-flowered spike, 5 cm long or more, pubescent; peduncle grooved; bracts triangular, acuminate; flowers solitary, axillary, with two lateral, sterile bracteoles; sepals 3, minute, mucronate; stamens numerous, united in fascicles or bundles which at base are connate into a common trunk, unilocular. Female inflorescence an elongated, pauciflorous spike, to 7 cm long; flowers sessile, axillary, bracteate; sepals 5, ovate, 1.5-2 mm long, acuminate, imbricate, abaxially puberulous; ovary globose, trilocular, 2 mm in diameter; style tripartite, 5 mm long, strongly papillate, basally united over a short distance. Fruit a globose capsule, 4 mm in diameter, puberulent, tricoccous. Seed ovoid, 2 mm long, crustaceous. In its natural habitat it is regularly flooded, at least annually. Its extended root system protects it against uprooting during floods; even floods that completely submerge the shrub during the rainy season for up to 9 months per year can be withstood (such plants are called 'rheophytes').

In seasonal climatic conditions H. riparia is deciduous. In Vietnam it flowers from April to June and fruits from August to October. In West Java flowering and fruiting is from June to November, in Central Java it flowers from June to October and fruits from September to April. Most plants are unisexual, but sometimes male and female flowers can be found on the same plant.

As to the stream bed soil, H. riparia seems to have no preferences; it occurs on sand, granite, shale, andesite, and other volcanic-derived material, but also on calcareous soil.

H. riparia is restricted to river banks, lake shores and rocky stream beds. It is found under ever-wet and seasonal climatic condition, preferring exposed sunny sites on stream banks and in stream beds in not too deep or too swift streams.

It can be propagated by seed and by cuttings.

Erosion control: Because of its long and extended root system, H. riparia is planted along rivers and streams to stabilize and protect the banks.

Fibre: In Southern China the bark is used as rope. Food: Leaves are eaten as a vegetable in the Philippines. Fuel: Stems and branches provide firewood. Medicine: H. riparia provides a number of popular local medicines. In Laos, a decoction of the leaves is used against itches. In Cambodia, the stems and leaves are applied as a purgative, whereas an infusion of the wood is used against malaria and scabies. In Java, leaves were used to blacken teeth and to fix loose ones. The pounded leaves and sometimes fruits are applied as a poultice against skin diseases in Malaysia, Thailand and Cambodia. A decoction of the leaves and fruits is similarly effective. Other products: In Sabah the root is used to make handles. Fodder: Leaves can be used for fodder as well. Lipids: Young shoots and leaves are a component of a hair oil in Cambodia.