Quick Facts

Quick facts

  • Wakame (Undaria pinnatifida) is a golden brown kelp growing up to 3 metres high.
  • It is introduced in Tasmania and Victoria, and may well spread as a result of coastal shipping.
  • Wakame is distinguished from native kelp (Ecklonia radiata) by a midrib up to 3 cm wide running though the blade.
  • Fertile plants have a distinctive sporophyll at the base of the plant.
  • It is spread by hull-fouling; potentially impacting native species by competing for space.

What Does It Look Like?

What is it?

Wakame (Undaria pinnatifida) is a brown seaweed kelp that grows to 1–3 metres in height. Plants are a golden brown colour and consist of a holdfast, cylindrical stipe (stem) and flattened, branched blade, with the stipe extending as a mid-rib through the blade. Fertile plants produce frilly sporophylls (leaves that produce spores) on the stipe (Hewitt et al. 2002).

For further information and assistance with identification of Wakame contact the herbarium in your state or territory.

Flower colour

No flower

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Wakame is a marine species that grows on hard surfaces from the inter-tidal to depths of about 20 metres (e.g. reefs, rocks, shells, ropes, wharf piles, ship hulls). It can form dense stands in sheltered areas. It does not grow well in areas of high wave energy or where native seaweeds are abundant (Hewitt et al. 2002).

Are there similar species?

Wakame is similar in appearance to the native common kelp (Ecklonia radiata). It can be distinguished by the presence of a distinct mid-rib and, when reproductive, a frilly spore-bearing blade (known as a sporophyll) surrounding the stipe (Department of Fisheries, Government of Western Australia 2006).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Wakame tends to form dense forests, resulting in competition for light and space which may lead to exclusion of native species. It will also foul marine infrastructure such as vessel hulls and aquaculture structures (Hewitt et al. 2002).

How does it spread?

Wakame is thought to have spread to, and within, Australia primarily by hull fouling (transported from infected areas by attaching to the hulls of ships) (Hewitt et al. 2002).

What is its history in Australia?

Wakame was first sighted in Tasmania in 1988 (Sanderson 1990) although it may have been present since 1982 (Department of Fisheries, Government of Western Australia 2006). Subsequently it was discovered in Port Phillip Bay, Victoria in 1996 (Campbell et al. 1999). It is thought to have arrived as a fouling organism on ship's hulls and then been subsequently distributed by similar means (Campbell & Burridge 1998).

How To Manage It?

Best practice management

Non-chemical control: Manual control: Wakame can only be controlled by physical removal, although this is largely unsuccessful (McEnnulty et al. 2001). 

Chemical control: Chemical biocides have been trialed, but these made no appreciable impact, and are labour intensive (Sanderson 1996; Burridge & Gorski 1998; McEnnulty et al. 2001). Please see the Australia Pesticides and Veterinary Medicine Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Wakame has a heteromorphic life history, meaning that there are two free-living phases. The conspicuous phase is the sporophyte (the spore-producing, diploid phase), which alternates with a microscopic gametophyte (the gamete-producing, haploid phase). It is an annual species, the sporophyte usually present through the late winter to early summer months and the microscopic gametophyte present during the colder months. The sporophyte blade degenerates in late summer, leaving only the sporophyll (the specialized spore-bearing structure) and holdfast (Schaffelke et al. 2005).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Wakame currently occurs on the east coast of Tasmania and in several bays in Victoria (Hewitt et al. 2002). Based on its wide temperature tolerance (Hewitt et al. 2002), it could spread to other areas.

Where does it originate?

Wakame is native to Japan, China and Korea (Silva et al. 2002).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Undaria pinnatifida

Other scientific names (synonyms)?

Undaria spp.

Does it have other known common name(s)?

Undaria Seaweed, Japanese Seaweed, Japanese Kelp

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