Monochoria C. Presl
monochoria, false pickerel weed, oval leaf pondweed
Africa, Asia to Australia
Species commonly cultivated
Monochoria australasica Ridl. (northern Australia)
M. cyanea (F. Muell.) F. Muell. (Australia)
M. hastata (L.) Solms (Asia to Australia)
M. korsakowii Regel & Maack (Asia)
M. vaginalis (Burm. f.) C. Presl (Asia to Australia)
U.S. Federal Noxious Weeds: Monochoria hastata, Monochoria vaginalis
Identification: Leaves of M. vaginalis leaves are linear to ovate, with a rounded to cordate base, while those of M. hastata are sagittate or hastate. The leaf blades of mature plants of these two species are good diagnostic characters, but due to the polymorphic phenology of species in this genus and the fact that other species can have similar looking leaves, care should be taken in identifying specimens within this genus. However, Monochoria is easily differentiated from Heteranthera by its flowers with 6 stamens, while Heteranthera flowers have 3.
Monochoria korsakowii is naturalized in Europe (Russia, Italy), while M. vaginalis is introduced into California (United States).
Monochoria vaginalis and M. hastata are often weeds in rice fields. Both species are aquatic weeds on the U.S. federal noxious weed list.
Annual or perennial. Stem floating, creeping, or erect, compact or elongate. Leaves in a basal rosette, sheathed at base, shape and size highly variable, linear to petiolate with distinct blade, ovate to lanceolate, venation palmate or parallel; base rounded to cordate to sagittate; margin entire. Inflorescence a raceme or umbel-like, subtended by 2 spathes; spathe shape variable, upper spathe reduced, lower spathe sometimes enclosing upper and inflorescence appearing to emerge from petiole (i.e. lower spathe). Perianth shortly tubular, of 6 tepals in 2 whorls of 3, purple, blue, or white. Dispersal by numerous seeds.
shallow, still waters; common in ephemeral water bodies