Homonoia riparia Lour.
Family
Euphorbiaceae
Synonyms
Adelia neriifolia Heyne ex Roth, Lumanaja fluviatilis Blanco, Ricinus salicinus Hassk.
Vernacular Names
| Malaysia | Kelereh, mempenai, kayu suarah. |
| English |
Water-willow. |
| Indonesia | Sobah (Javanese), jurai (Sundanese), sangkir (West Sumatra). |
| Philippines |
Agukuk, agoyoi, managos (Tagalog). |
| Myanmar |
Momakha. |
| Cambodia | Réi tuk. |
| Laos |
Kh’aiz fa:d. |
| Thailand |
Khrai-nam, khrai-hin (peninsular), khrai (central, northern). |
| Vietnam |
Ru ri, ri ri, cay ru ri nuoc. |
Geographical Distributions
Homonoia riparia is widely distributed in Asia from India through Indo-China and southern China to Taiwan and from Peninsular Malaysia, throughout Indonesia and the Philippines to Papua New Guinea.
Description
Homonoia riparia is a gregarious shrub or small, crooked and twisted tree that can grow 1-4 m tall and up to 10 cm in stem diametre. It forms a woody, deep and extensive root system. The branches are smooth to slightly grooved.
The leaves are arranged alternate and simple. The stipules are keel-like, enlarged at base, measure 5-6 mm long and caducous. The petiole is 5-15 mm long and pubescent. The blade is narrowly lance-shaped to oblong, measuring 4-20 cm x 1-2.5 cm, obtuse or rounded at the base, acuminate, obtuse or mucronate at apex, bright green, penninerved, thin and chartaceous. The upper surface is shiny and smooth while the lower surface is pubescent, closely becoming hairless, minutely lepidote and with entire or dentate margin.
The male inflorescence is an axillary and densely-flowered spike. It is 5 cm long or more and pubescent. The peduncle is grooved, with triangular bracts and acuminate. The flowers are solitary, axillary, and with two lateral and sterile bracteoles. The 3 sepals are minute and mucronate. Numerous stamens are united in fascicles or bundles into a connate into a common trunk at the base. The female inflorescence is an elongated, pauciflorous spike and measures up to 7 cm long. The flowers are sessile, axillary and bracteate. There are 5 ovate sepals measuring 1.5-2 mm long. They are acuminate, imbricate and abaxially hairy. The ovary is spherical, trilocular and measures 2 mm in diametre. The style is divided into 3 parts. It is 5 mm long, strongly papillate and basally united over a short distance.
The fruit is a spherical capsule which is 4 mm in diametre, hairy and tricoccous. The seed is 2 mm long, ovoid and crustaceous.
Ecology / Cultivation
Homonoia riparia is restricted to river banks, lake shores and rocky stream beds, from 50-500 m altitude. 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’). It is found under ever-wet and seasonal climatic conditions, preferring exposed sunny sites on stream banks and in stream beds in streams not too deep or too swift. As to the streambed 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.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No.11: Auxiliary plants.
