Monochoria

Scientific name

Monochoria C. Presl

Common names

monochoria, false pickerel weed, oval leaf pondweed

Family

Pontederiaceae

Similar genera

Eichhornia, Heteranthera, Limnocharis, Ottelia (juvenile floating leaves), Pontederia, Sagittaria

Native distribution

Africa, Asia to Australia

Species cultivated

Monochoria australasica Ridl.

M. cyanea (F. Muell.) F. Muell.

M. hastata (L.) Solms

M. korsakowii Regel & Maack

M. vaginalis (Burm. f.) C. Presl

U.S. Federal Noxious Weeds: Monochoria hastata, Monochoria vaginalis

Identification: Leaves of M. vaginalis leaves are linear to ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, with a rounded to cordatecordate:
(adj) heart-shaped; in the form of two rounded lobes
base, while those of M. hastata are sagittatesagittate:
(adj) shaped like an arrowhead
or hastatehastate:
(adj) (of a leaf) with a narrow, pointed lamina with two basal lobes spreading more or less at right angles to the petiole
. The leaf blades of mature plants of these two species are good diagnostic characters, but due to the polymorphicpolymorphic:
(adj) displaying multiple forms (of, e.g., an organ) in one organism
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.

See M. hastata disseminule fact sheet.

See M. vaginalis disseminule fact sheet.

Adventive distribution

Monochoria korsakowii is naturalized in Europe (Russia, Italy), while M. vaginalis is introduced into California (United States).

Weed status

Monochoria vaginalis and M. hastata are often weeds in rice fields. Both species are aquatic weeds on the U.S. federal noxious weed list.

Habit

attached, floating, or emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
rosette plant

Brief description

Annual or perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
. Stem floating, creeping, or erect, compact or elongate. Leaves in a basalbasal:
(adj) at or pertaining to the base, or point of attachment
rosette, sheathed at base, shape and size highly variable, linear to petiolatepetiolate:
(adj) relating to or in the form of a petiole; bearing petioles
with distinct bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
, ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
to lanceolatelanceolate:
(adj) lance-shaped; widest point below the middle, tapering to the apex
, venationvenation:
(n) the arrangement of veins in a leaf
palmatepalmate:
(adj) (of leaves or venation) with lobes, leaflets, divisions or veins originating from the same point
or parallel; base rounded to cordatecordate:
(adj) heart-shaped; in the form of two rounded lobes
to sagittatesagittate:
(adj) shaped like an arrowhead
; marginmargin:
(n) edge; rim
entireentire:
(adj) having a continuous margin that is not toothed or lobed
. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
a racemeraceme:
(n) an indeterminate, unbranched inflorescence having pedicelled flowers on a usually elongated axis (may be cymose)
or umbel-like, subtended by 2 spathes; spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
shape variable, upper spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
reduced, lower spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
sometimes enclosing upper and inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
appearing to emerge from petiolepetiole:
(n) the stalk of a leaf
(i.e. lower spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
). Perianthperianth:
(n) collective term for the calyx and corolla of a flower; also used for floral whorl(s) in which the calyx and corolla cannot be resolved; any of the leaves or bracts surrounding the sex organs of bryophytes
shortly tubulartubular:
(adj) (of a corolla, perianth, calyx tube or other structure) (1) tube-shaped; cylindrical: narrow and elongate with more or less straight sides; (2) having segments fused into a tube (of any shape)
, of 6 tepals in 2 whorls of 3, purple, blue, or white. Dispersal by numerous seeds.

Natural habitat

shallow, still waters; common in ephemeral water bodies

Additional comments

Monochoria contains seven species, of which five are cultivated for ponds. The foliage of Monochoria is used as a medicinal herb and as a vegetable.