Hygrophila

Hygrophila costata

Description
Emergent to 1.5 m high.
Leaves:
■ Opposite leaves
■ To 1.8 cm long, 0.3 cm wide
■ Prominent midrib
■ Generally hairy lower surface
Flowers:
■ Inconspicuous whitish flowers
■ In whorls in leaf axils (stem and leaf junction)
■ Year round
Stems:
■ Four-angled and generally hairy
Similar looking species
■ Alligator weed (Alternanthera philoxeroides):
white flower on stalk, completely hollow
stems
■ East Indian hygrophila (Hygrophila
polysperma): sprawling habit, smaller leaves
(0.7–8 cm long), variable leaf colour, bright
green to brown to reddish
■ Senegal tea (Gymnocoronis spilanthoides):
irregularly toothed leaf margins, ribbed stems
that are hollow between the joints, halfsphere-shaped (pom-pom-like) white or pale
purple flower heads in clusters
■ #Smart weed (Persicaria decipiens): alternate
hairy leaves
■ #Water primrose (Ludwigia peploides ssp.
montevidensis): yellow flowers, alternate
glossy leaves
Background
Hygrophila is native to the region from southern
Mexico to Argentina. It is an aggressive aquatic
or semi-aquatic plant that forms mats of dense
growth around the margins of watercourses.
It was sold as an aquarium plant and has been
collected in Australia only since the 1990s,
suggesting that it is a recent naturalisation.
Distribution
Hygrophila has naturalised and became a weed
in south-eastern Qld and north-eastern NSW.
Means of spread
Spreads by fragments and by water-dispersed
seed. The sticky seeds may also adhere to
wildlife, machinery, watercraft and humans.
Spreading stems sprout new roots from nodes
when in contact with the soil.
Declaration status
NSW: C2(55); WA: Unass; Qld: C1
If found, report this weed to your local weed


Source: Recognising Water Weeds
Plant Identification Guide
Aquatic Weeds Early Detection Project
Compiled by Jessica Grantley, Fiona McPherson and
Andrew Petroeschevsky,

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