Sharing banned aquatic plants illegal

Bay of Plenty residents are being urged not to share or grow banned aquatic pest plants which pose a “huge” risk to the region’s waterways.

The Ministry of Primary Industries and the Bay of Plenty Regional Council is particularly concerned about salvinia, also known as kariba weed, and water hyacinth.

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 swamps.

The floating mats can double in size within a few days and pose flooding risks, as well as 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 authorities concerned that they are being propagated and distributed among pond owners.

“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.”

Emmanuel says people need to be aware that growing or sharing salvinia and water hyacinth undermines efforts to eradicate the 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.

Visit or 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.


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