Aquatic Weeds are everyone's responsibility...
Weed identification is important in the care and maintenance of any
pond. But more importantly realizing the
potential of a plant to become a weed can assist in the prevention or minimise
the risk to the environment through careful management.
As Australia's largest wholesale producer of waterlilies and other pond
plants, we are the industry leader. As
such, we are recognised as the main source of information, that people look to,
for guidance. Oz Watergardens continues to work with the Nursery industry and the Government departments to
update the aquatic weeds database. We are working together to help people
understand how to recognise aquatic weeds and
what they should do to help control the risk of potential aquatic weeds.
Aquatic weeds are classified according to 3 catagories.
- Declared noxious weeds,
- those that should be
- those that should be
monitored as potential weeds.
The potential of any aquatic plants to become aquatic
weeds can vary greatly. Some
produce an abundance of seeds that are easily spread. Some are such vigorous growers, that they
choke out all other plants. While
others, are only aquatic weeds in specific areas,
but not others.
To highlight this, let's look at Water Hyacinth (Eichhornia crassipes). This plant is a "Declared Weed" throughout all
of Australia and has on occasions cost a lot in both money and resources to
bring it under control.
Why is it declared a weed? Water
Hyacinth grows vigorously in warm nutrient rich water. It has been recorded as one of the worst
weeds in global history. There have been
many examples, where this weed has spread hundreds of kilometres in large river
(Below is an example of an outbreak close to the city of Melbourne, Victoria)
Water hyacinth float on the water surface and continuously produce new
plantlets that are attached to the original mother plant. This growth results in large mats
that become so thick that they choke and block entire rivers, making them
impenetrable to even the largest of boats.
When the water surface is covered with such dense vegetation, many
problems occur. The health of the water
is reduced through less oxygen being available and significant changes to the
water chemistry occur through their high nutrient uptake. Aquatic life in the water struggles in the
poor quality water. Bird life cannot
feed. Mosquito populations
increase. Other plants become choked or
cannot get any sunlight. Decaying or
dying plant material causes further water pollution.
The fact that one plant dominates, upsets the whole ecological balance
and can cause both plants and animals that rely on the system to die out or be
significantly reduced. The cost of the clean up can be very expensive too (see image above).
Water Hyacinth is a State prohibited weed in Victoria and there are serious consequences including large fines for those who distribute or sell these plants.
The Department of Primary Industries (DPI) is responsible for the treatment and removal of this species.
Please report any sightings of Water hyacinth in Victoria to DPI immediately on 136 186
Water Lettuce (Pistia stratiotes) is another floating aquatic plant
capable of causing problems similar to the Water Hyacinth. However, understanding the growth habits of
this plant, helps us to manage its weed potential. Water Lettuce only survives in warmer
climates. In areas where the Winter temperatures fall
below 18°C for longer than a month, the Water Lettuce plants wither and die. This key factor, is the reason
why it is not declared an aquatic weed in all areas.
Unfortunately there is no one up to date website, listing all the
Declared and potential aquatic weeds in all
parts of Australia. Currently you need
to refer to your individual state government agriculture departments. We have even had problems trying to get
accurate information ourselves and even had instances where different
departments within the same regions have different lists.
We continue to work with and support the various agencies to develop a national register
of aquatic weeds, but understand that it will
For the moment, we recommend going to the www.weeds.org.au website.
Go to the Noxious Weeds List, then go to Click here for the entire Noxious Weeds List in pdf format.
If you would like to down load a copy of the Aquatic Weed Identification Guide for Victoria Click Here.
The control of aquatic weeds is a
challenge, due to the highly sensitive nature of the environment they are found
in. Unlike terrestrial weeds where many
herbicides and other equipment can be used.
The aquatic environment restricts the use of heavy equipment and many
herbicides are unsafe to use near waterways, due to the harm that they cause to
other life such as frogs and fish.
Algae can also be a major
concern for most pond owners. Algae
are much simpler plants and more sensitive than larger plants. Therefore, carefully applied, low dose algal
treatments harm the algae but are still below levels that would affect larger
plants. Various algal treatments and
products are available. However, the
best solution is to establish a healthy ecological balance in your pond. Let nature do its job, with only a little
help if necessary.
For further information on algae and algae control go to our Tip
and Hints page.
Declared and noxious Aquatic weeds of Australia,
information can be found on www.weeds.org.au