Actinoscirpus grossus (L.f.) Goetgh. & D.A. Simpson
Scirpus gross L.f., Hymenochaete grossa (L.f.) Nees, Schoenoplectus grossus (L.f,) Palla.
Rumput menderong, rumput menerong, rumput morong.
Mensiang (western Sumatra), lingi (Javanese), walingi (Sundanese).
Tikiu, titiu (Tagalog), agas (Bikol).
|Thailand||Kok, kok prue, kok saamliam (Central, Bangkok).|
Chi c[os]i d[uf]i.
Actinoscirpus grassus probably originated in Southeast Asia and is widely distributed in the Old World tropics from India, Sri Lanka and southern China throughout Southeast Asia to the Bonin Islands (south of Japan), Micronesia and tropical Australia.
Actinoscirpus grassus is an erect, stout, rhizomatous perennial herb that can grow up to 2 m tall. The stem is sharply 3-angled with concave sides, measuring 80-200 cm x 0.5-2.5 cm, smooth, spongy, strongly septate-nodulose, with a corm-like enlargement at base, and singular growing in small groups or in dense tufts.
There are a few leaves which are sheathed and pale yellow with spongy sheath, prominently septate-nodose and tightly surrounding the stem base. The blade is sublinear and measuring 50-180 cm x 1-3 cm. The lower half is keeled and 3-sided, somewhat thickish, soft and strongly septate-nodulose while the upper half is almost flat and gradually acuminate, and with subscabrous margin.
The inflorescence is 6-15 cm long, terminal, and corymbiform with primary, secondary and tertiary rays. There are 3-4 involucral bracts which are leaf-like, flat, linear, 15-70 cm long and with at least 2 overtopping the inflorescence. There are several primary rays which are spreading, unequal and scaberulous while the secondary rays are 1-4 cm long. There are numerous spikelets which are solitary, peduncled except for terminal ones, ellipsoidal, measuring 4-10 mm x 3.5-4 mm and with bisexual flowers.
The glumes are spirally arranged, appressed, concave-ovate, measuring about 3 mm x 2 mm, membranous, nearly smooth, prominent and with green midrib, red-brown with finely ciliolate margins and with obtuse to short mucronulate apex. There are 4-6 hypogynous bristles (perianth) which are retrorsely scabrous and slightly longer than the fruit. There are 3 stamens which are very short, and with linear anthers about 1 mm long. The style is 3 mm long.
The fruit is a nutlike, trigonous, obovate achene that measures about 1-2 mm x 1 mm, apiculate and brown.
Actinoscirpus grossus occurs, often abundantly, in swampy or inundated locations, pools, ditches and rice fields, from sea level up to 900 m altitude. It is an important aquatic weed in Southeast Asia. In Indonesia, it is considered a weed of minor importance in lowland-irrigated and tidal rice fields, where it can be controlled manually, by deep-ploughing before seed formation, or with herbicides. In Peninsular Malaysia, it is one of the major weeds of transplanted rice.