Growing and sharing banned aquatic plants is illegal
The Ministry for Primary Industries and Bay of Plenty Regional Council are urging residents not to grow or share banned
aquatic pest plants because they pose a huge risk to our waterways. They are particularly concerned about salvinia (also
known as kariba weed) and water hyacinth.
Both weeds are present in the Bay of Plenty and are known for growing rapidly to form large dense floating mats on
ponds, drains, lakes and still waters in swamps. The floating mats can double in size within days and pose flooding
risks and drowning risks to humans and livestock.
Recent discoveries of the weeds at a number of locations including farm ponds in the Auckland and Northland regions has
the Ministry and Bay of Plenty Regional Council concerned that these weeds are being propagated and distributed among
‘‘We are concerned at the extent of the spread of these aquatic weeds,’’ says Ministry for Primary Industries response
manager Emmanuel Yamoah.
“Anyone who sees any of these weeds in the Bay of Plenty, or suspects they may be present, should report it to either
Bay of Plenty Regional Council on 0800 884 880 or Ministry for Primary Industries on 0800 809 966. Ministry for Primary
Industries contractors or Bay of Plenty Regional Council biosecurity staff will visit the site and remove the weeds free
of charge if they find them.”
Dr Yamoah says people need to be aware that growing or sharing salvinia and water hyacinth really undermines efforts to
eradicate these serious weeds.
“They are among the world’s most invasive weeds and have the potential to cause huge damage to our waterways, native
aquatic plants and the fish that live in these waterways. The weeds can impact adversely on hydro-electricity generation
and irrigation. They can clog waterways, making boating, fishing, recreational use and almost all other water activities
impossible. Countries where these weeds have established spend millions of dollars annually to control them.”
Both plants have been declared unwanted and notifiable organisms under the Biosecurity Act 1993, which makes it illegal
to sell, propagate or distribute them. They are also banned under Bay of Plenty Regional Council’s Pest Management Plan.
for more information and photos of the pest plants.
Information about Salvinia and water hyacinth
Salvinia is a small, free floating aquatic fern with branched, horizontal stems that lie just below the water surface. The upper
surface of the leaf is covered with distinct white hairs. It has a root-like structure underneath each leaf pair and as
the plant matures, these ‘roots’ resemble wet hair. The plant grows usually up to 30cm long.
Water hyacinth is a floating aquatic perennial, with distinctive bladder-like swollen leaf petioles giving buoyancy. It has shiny
rounded leaves with thick masses of feathery dark roots which can reach 2.5m in length. A single flowering stalk with a
cluster of mauve-blue flowers, each with a yellow spot, is produced above the foliage. Plants produce floating
horizontal stems from which new plants arise.