Undaria pinnatifida


Also known as:

Wakame, Japanese kelp, Asian seaweed

Family: Alariaceae

Origin: North-east Asia and Russia

The undaria has long seaweed leaves on either side of a brown midrib.
Undaria is a species of kelp that is native to Japan. Mainly found in the low intertidal area to a depth of 15 metres.
Photo credit: CSIRO

Regional Pest Management Plan (RPMP) status

  • Whole region — Sustained control

View more about the RPMP statuses

General description

A large seaweed that grows to 1-2 metres long. Mature plants are golden brown to green-brown in colour, crinkly in appearance and have a distinct midrib.

What you need to know

To help protect our environment, you must not breed, distribute, release or sell any Undaria within the Auckland region. Applies only to live propagules. Processed food products may still be sold.

If you’re in charge of any craft in the Auckland region you must:

  • ensure that the level of fouling on the hull and in niches of the craft does not exceed ‘light fouling’
  • ensure that it is free of all ballast water, bilge water, holding tank water or sea water held in any other container when entering any marine body from the land.


Can tolerate a broad range of temperatures and light levels and grow on a variety of surfaces. It can produce millions of spores and is also frequently transported as biofouling on vessels.

Impact on environment

It can spread rapidly and form dense underwater forests; outcompeting native canopy-forming algal species, altering habitats and impacting associated marine faunal communities.



Before moving your boat or other craft to new locations, make sure the hull, anchor chain and all other equipment on board is clean and free of marine pests or other fouling. Think about where you’re taking on or releasing ballast, bilge or holding tank water, or water in any other container such as chilly bins, to avoid spreading marine pests.

For more information on Undaria and how to avoid spreading them, please visit Prevent pests from spreading or contact Auckland Council at pestfree@aucklandcouncil.govt.nz.

The undaria underwater in a large cluster.
Undaria is known as 'the gorse of the sea'.
Photo credit: K. Neill & S. Miller, NIWA