Hydrothrix

Scientific name

Hydrothrix Hook. f.

Family

Pontederiaceae

Similar genera

Bacopa (rarely confused), Egleria, Hydrotriche, Lagarosiphon, Mayaca, Rotala

Native distribution

eastern Brazil

Species cultivated

Hydrothrix gardneri Hook. f.

Adventive distribution

none

Weed status

not weedy

Habit

submerged, delicate, rooted stem plant

Brief description

Annual. Delicate narrow branching stems, with adventitiousadventitious:
(adj) of an organ growing where it is not normally expected, e.g., roots growing from a stem
roots produced at nodes. Leaves in whorls of 7-30, regularly spaced along entireentire:
(adj) having a continuous margin that is not toothed or lobed
stem, 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)
elongate, linear, sheathed at base. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
axillaryaxillary:
(adj) in, of, or produced from an axil
, subtended by a green spathespathe:
(n) a large bract or bracts subtending and often enclosing an inflorescence
. Flowers paired (superficially appearing as a single flower); 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
tubular, of 6 tepals in 2 whorls of 3, lobes unequal, yellow. Flowers are self-fertilized if they are unopen (cleistogamous) under water, or they open above water and are fertilized by insects. Dispersal is by seed.

Natural habitat

still or slow-moving waters such as lakes, ponds, and large rivers

Additional comments

The only species in the genus Hydrothrix, H. gardneri is a delicate plant that is rarely cultivated in aquaria, although it is surprisingly easy to propagate from stem fragments or seed. Recently H. gardneri was transferred to Heteranthera based on moprhological and phylogenetic evidence.