Rotala

Scientific name

Rotala L.

Common names

rotala

Family

Lythraceae

Similar genera

Bacopa, Clinopodium, Cuphea, Didiplis, Elatine, Hemianthus, Hydrothrix, Lythrum, Mayaca, Micranthemum

Native distribution

almost cosmopolitan

Species cultivated

Rotala indica (Willd.) Koehne

R. macrandra Koehne

R. mexicana Schltdl. & Cham.

R. occultiflora Koehne

R. rotundifolia (Buch.-Ham. ex Roxb.) Koehne

R. wallichii (Hook. f.) Koehne

Adventive distribution

R. indica is recorded in rice fields in the United States (CA, LA), Europe (Italy, Portugal), and Africa (Congo); introduced in Australia, but not naturalized.

R. rotundifolia is introduced in the United States (AL, FL) and Australia.

Weed status

Members of this genus are sometimes recorded as weedy in rice fields and irrigation ditches.

Habit

amphibious, creeping, erect or ascending stem plant

Brief description

Stem erect, creeping or emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
. Leaves oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, decussatedecussate:
(adj) arranged along stem in pairs, with each pair at right angles to the pairs above and below
, sometimes whorledwhorled:
(n) bearing whorls; a type of leaf arrangement (phyllotaxis) in which leaves are in whorls
, usually sessilesessile:
(adj) attached directly, without a stalk
; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
shape variable: capillarycapillary:
(adj) slender, hair-like
, oblongoblong:
(adj) two to four times longer than wide, with +/- parallel sides
to ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, green to dark red; distinctly heterophyllousheterophyllous:
(adj) with dissimilar leaves on the same plant; often occurs on plants with both submersed and emersed leaves
: submersedsubmersed:
see submerged
leaves typically narrower and thinner than emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
leaves. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
axillaryaxillary:
(adj) in, of, or produced from an axil
or a spikespike:
(n) an indeterminate, unbranching inflorescence of sessile flowers or flower clusters on a usually elongated axis
or racemeraceme:
(n) an indeterminate, unbranched inflorescence having pedicelled flowers on a usually elongated axis (may be cymose)
. Flowers actinomorphicactinomorphic:
(adj) of flowers, having radial symmetry; capable of being bisected into identifical halves along more than one axis
; sepals fused, calyxcalyx:
(n) the outer whorl of the perianth; all the sepals of a flower
tube variously shaped, lobes usually 4; petals present, pink or white or absent. Dispersal by seed or stem fragments.

Natural habitat

still, shallow waters and water margins, also wet soil

Additional comments

Rotala is a large genus of ca. 46 species, but only four or five are commonly traded in the industry under confirmed species names. Many other species are culitvated but specificspecific:
(adj) pertaining to a species
names are unknown at present. Many species are wetland herbs. Rotala wallichii is easily differentiated by its needle-shaped submersedsubmersed:
see submerged
leaves and white flowers. Rotala rotundifolia has ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
to elongate submersedsubmersed:
see submerged
leaves, ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
leaves, and pink flowers. Rotala macrandra has very broad ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
leaves on submersedsubmersed:
see submerged
and emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
stems (wavy in submersedsubmersed:
see submerged
form) and lacks flower petals. Rotala mexicana has ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
to narrow elongate leaves in both submersedsubmersed:
see submerged
and emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
forms and also lacks flower petals. Rotala rotundifolia is often sold as R. indica. Rotala sp. 'Nanjenshan' appears to be a possible natural hybridhybrid:
(n) a specimen produced by the sexual reproduction of two plants of different species or subspecies
of R. wallichii and R. rotundifolia, known only from a single location in Taiwan. Rotala rotundifolia has distinct red and green leaved varieties.