Monochoria vaginalis: Monochoria vaginalis (syn. Pontederia vaginalis, Boottia mairei, Gomphima vaginalis)

Family:  Pontederiaceae (pickerel weed family).

Common names: Pickerel weed, monochoria, heartshape false pickerelweed.

Thai:  ขาเขียด Kha khiat, ผักเขียด Phak khiat, นิลบล Ninlabon (Central); ผักเป็ด Phak pet (Chon Burit), ผักเผ็ด Phak phet (Nakhon Ratchasima); ผักริ้น Phak rin (Peninsular); ผักฮิ้น Phak hin (Northern, Ubon Ratchathani); ผักฮิ้นน้ำ Phak hin nam (Northern);  Burmese: Ka-dauk-sat, Pa-dauk-sat;  Vietnamese: Rau mác lá thon, rau mác bao.

Annual or perennial aquatic herb, 10-50 cm tall; fleshy and shiny in appearance,  forming rosettes but stemless and with short rhizomes.

Leaves: Size and shape is highly variable (2-12.5 cm long x 0.5-10 cm wide); shiny, deep-green in colour with longitudinal veins and rigid, hollow petioles.

Flowers: Inflorescence 3-6 cm long, bearing 3 to 25 flowers which open underwater; each flower with six purple-blue tepals, which are the outer parts of the flower.

Fruit: A capsule (1cm long) containing many tiny winged seeds.

Seeds: Straw coloured to dark beige, tiny (1 mm long), oblong and longitudinally ribbed.

Origin: Native to Asia.

Introduced as: Used as a vegetable and cattle fodder.

Habitat: A plant of subaquatic to aquatic conditions; typically found in sunny sites in swamps, marshes, open wet places and along ditches.

Spread: By short stolons and by seed.

Invades:  A serious weed in rice fields in east and southern Asia.

Impacts: Monochoria vaginalis is a major weed in paddy rice. It grows rapidly and has discontinuous germination, which makes it difficult to control. At high densities of the weed, yield losses of up to 82% have been reported in rice.  Monochoria vaginalis is also a secondary host for the rice grassy stunt virus transmitted by the brown planthopper, Nilaparvata lugens, and the rice ragged stunt oryzavirus, as well as for the rice sheath rot pathogen Sarocladium oryzae.