Status of hornwort in Tasmania(Ceratophyllum demersum)
- Hornwort is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of hornwort are prohibited in Tasmania.
- The legal responsibilities of landholders and other stakeholders in dealing with hornwort are laid out in the Hornwort Statutory Weed Management Plan.
What does hornwort look like?
is a free-floating aquatic herb. The branched stems grow from 30 to 60
cm. The leaves are dark green, deeply divided into cylindrical segments
which are toothed on one side, and occur in whorls of 5 to 12 leaves.
The leaves are very crowded at the ends of stems so as to resemble a
bushy animal tail. The flowers are greenish and very small. There are no
roots; the roots are replaced by finely divided stem branches.
overwinters as slowly growing plants, seeds or turions (called winter
buds). Flowers are produced in summer but remain fully submerged.
is mainly by vegetative means although seed can also be produced. Most
spread is via stem fragments or turions which can be broken off by wave
motion, foraging animals or boat propellers and floated downstream. Each
stem fragment and turion can produce a new colony.
Image top: Hornwort, photo: Doreen L. Smith
Image above: Hornwort stem, photo: Neal Kramer
Impacts of hornwort
- Hornwort is a
native plant in ponds, dams and streams on mainland Australia, and only
becomes a weed when the freshwater system is altered, particularly where
nutrient levels are enriched.
Where does hornwort occur?
- Hornwort is a native on mainland Australia and occurs in all States.
- Hornwort has not naturalised in Tasmania.
What you need to do
- If you locate
hornwort anywhere in Tasmania, or if you find a plant that you think
could be arrowhead, immediately contact your Regional Weed Management
Officer on 1300 368 550 to report this weed.
Hornwort Statutory Weed Management Plan
Weed Links and Resources
Other useful links
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