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JAPAN JABARA: INVADER OF WATER RESOURCES
Stems
The stems thick, fleshy, produce
horizontal stolons which develop
a further rosette of leaves from a
terminal bud.
Flowers
Picture 1: Japan Jabara Plant
We all know this water plant commonly
found in Sri Lankan waterways,
irrigation canals, rivers and tanks
around the country. The common
name of this highly invasive plant is
water hyacinth and botanically named
as EICHHORNIA CRASSIPES. This
plant is the worst water weed in the
world and the most dominant and
widely distributed invasive aquatic
plant in Sri Lanka. It was bought to
Sri Lanka by colonial governor’s wife
lady Blake in 1901 due to its beautiful
flower. Then it was introduced to the
Botanical garden at Peradeniya as
an ornamental species. By 1909, the
plant was reported around Kandy and
Kegalle districts in invading water
resources. When the occurrence of
this weed was recorded in Southern,
Northern, Western, Central and
Sabaragamuwa provinces, it was
declared as a weed under the newly
enacted Plant Protection Ordinance
No. 10 of 1924. Despite several
expensive eradication campaigns, the
weed was found throughout the low
lands by 1933. Infestations remained
widespread, numerous and flourishing
throughout last few decades.
Japan Jabara was first detected in
1890 in Australia (few localities in
New South Wales and Queensland). It
has since spread into many locations
on Australia’s east coast region
and declared as a weed of national
significance.
Japan Jabara was originated in Brazil
and surrounding countries of South
America and distributed worldwide
as an aquarium plant in water tanks,
ponds and lake.
Lilac to blue flowers is clustered at
the top of the flower spike about 15
cm long. Many populations seem to
flower twice in an annual season. The
flowers have six stamens, three long
and three short. Flowers last only a few
days. The flower stalk then bends over
into the water and many small seeds
form in the submerged head. Fruit is a
narrow, 3 celled capsules about 1-1.5
cm long, containing up to 300 seeds.
Seed is more or less ovoid and 1- 1.5
mm long with many longitudinal ribs.
Roots are black to purple and feathery,
emerging from a rhizome or crown,
hanging in the water to 1 m long. In
and abundance of phytoplankton
under large mats, ultimately affecting
fisheries.
•Large japan jabara mats prevent the
transfer of oxygen from the air to
the water surface or decrease oxygen
production by other plants and algae.
When the plant dies and sinks to the
bottom the decomposing biomass
depletes oxygen content in the water
body. Dissolved oxygen levels can
reach dangerously low concentrations
for fish that are sensitive to such
changes.
•Floating mats of japan jabara support
organisms that are detrimental to
human health. The ability of its mass
of fibrous, free floating roots and
semi submerged leaves and stems
to decrease water currents increase
breeding habitat for the malaria
causing mosquitoes.
•Japan Jabara often clogs waterways
due to its rapid reproduction
Picture 3: Impacts of Japan Jabara in a waterway
It is a free floating water plant that
grows in ponds or slow moving
waterways. It is a perennial monocot
that belongs to the Pontederiaceae
family.
Leaves
The leaves are shiny, 4 – 25 cm long
and wide, circular on short, bulbous,
spongy petioles. As the plants become
crowded together, the leaf petiole tends
to lengthen and the bulbous swelling
disappears. Under good conditions,
the petioles of plants in this form can
exceed a metre in length. Buoyant, old
leaves and flowers get pushed below
water levels.
Picture 2: Japan Jabara at flowering
shallow water the roots may become
attached to the bottom mud.
Japan Jabara is capable of explosive
rates of spread. Under favourable
conditions, it can be double its mass
every 5 days forming new plants on
the ends of stolons. It also grows from
seed which can remain viable for 20
years or longer.
and propagation rate. The dense
mats disrupt socioeconomic and
subsistence activities (ship and boat
navigation, restricted access to water
for recreation, fisheries and tourism) if
waterways are blocked or water pipes
clogged.
Seeds generally require sunlight,
oxygen and high temperatures
before they will germinate and these
conditions are found on exposed mud
banks and decaying masses or dead
weed materials. New plants can flower
within 3-4 weeks old.
Impacts
•Japan Jabara is challenging the
ecological stability of freshwater
water bodies, out-competing all other
species growing in the vicinity, posing
a threat to aquatic biodiversity. Beside
suppressing the growth of native plants
and negatively affecting microbes,
japan jabara prevents the growth
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DECEMBER 2013 PAHANA - LIGHT & LIFE
Pictures and Text By
Dr. Lalith Gunasekera, Invasive
Species Specialist
Bargara Beach, Bundaberg,
Queensland