Status of hydrilla in Tasmania(Hydrilla verticillata)
- Hydrilla is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of hydrilla are prohibited in Tasmania.
- The legal responsibilities of landholders and other stakeholders in dealing with hydrilla are laid out in the Hydrilla Statutory Weed Management Plan.
What does hydrilla look like?
is a submerged perennial (long-lived) aquatic plant which can grow as a
free-floating mat or attached to the bottom of the water body. The stems
are vertical and much branched and can grow to 8 metres depending on
water depth. Stolons (or runners) grow on or just below the mud surface
and produce tubers, while turions (readily detachable buds) grow on the
ends of stems. The leaves are produced in whorls of 4 to 6 along the
length of the branches, are brownish-green in colour and have minutely
- Plants are either male or female. Flowers grow
in the leaf axils near the ends of the branches. Female flowers rise to
the water surface on long floral tubes reaching 10 cm in length, while
the male flowers break off from the stems and rise to the surface where
they open explosively and release pollen.
- In temperate regions,
hydrilla overwinters as dormant shoots, tubers, turions and seed. These
commence growth in spring and rapidly grow into a thick mat of
interwoven stems which then die off in late autumn and winter.
spread is by vegetative means via stolons, tubers, turions and
fragmentation. Local spread of a plant occurs when stolons and tubers
germinate along the periphery of the clump. Long distance spread occurs
mainly when fragments of stem are dislodged and carried down-stream,
where they regenerate and form now plants.
Image top: hydrilla stems
Images above: whorls of hydrilla leaves; hydrilla flower
Photos: CDFA, 2001
Impacts of hydrilla
- Hydrilla is a
native on mainland Australia and is not usually weedy. However the plant
can become a serious weed where a water body is artificially enriched
with nutrients. Under these conditions, hydrilla can block inland
waterways, irrigation systems and hydro-electric installations, as well
as limit recreational access to waterways.
Where does hydrilla occur
- Hydrilla is a native to the Mediterranean, Africa, Asia and mainland Australia.
- Hydrilla has not naturalised in Tasmania.
What you need to do
- If you locate
hydrilla anywhere in Tasmania, or if you find a plant that you think
could be hydrilla, immediately contact your Regional Weed Management
Officer on 1300 368 550 to report this weed.
Hydrilla Statutory Weed Management Plan
Weed Links and Resources
Other useful links
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