Asian kelp

Asian kelp

Undaria pinnatifida

Common Name:

Asian kelp

Scientific Name:

Undaria pinnatifida

Alternative common names:

Wakame (Japanese), Japanese kelp (English) and apron-ribbon vegetable (English). 


Asian kelp is native to Japan where it is cultivated for human consumption. It is an opportunistic weed which spreads mainly by fouling ship hulls. It forms dense underwater forests, resulting in competition for light and space, which may lead to the exclusion or displacement of indigenous plant and animal species.

Additional Information

Where does this species come from?

Japan, China and Korea.

What is its invasive status in South Africa?

NEMBA - Category 1b.

Where in South Africa is it a problem?

Western Cape.

How does it spread?

Through international shipping and mariculture.

Why is it a problem?

It may cause displacement of native species. It can change the structure of ecosystems, especially in areas where indigenous seaweeds are absent. It is also said to have potential to become a problem for marine farms by increasing labour and harvesting costs due to fouling problems on fin fish cages, oyster racks, scallop bags and mussel ropes. Heavy fouling may also restrict water flow through cages.

What does it look like?

Asian kelp is a very large, golden-brown seaweed. Adult specimens can grow to a length of 1.5-3m in less than a year - a growth rate of up to 1cm per day. It is an annual species, with two life stages: microscopic male and female gametophytes and a macroscopic sporophyte, which is the form that we see. Typical features of the sporophyte stage are the distinct yellowish midrib, which reaches up to 1-3cm wide and forms a continuation of the stem, and the characteristic wavy, spore-forming blades around the base of the stem. Above the stem, the midrib runs the entire length of a large, leaf-like blade, which is feathery in appearance and can reach 50-100cm long. This part of the plant is symmetrically divided into a large number of lobes, resembling a succession of leaves. Special gland cells develop early on, appearing as small, dark dots on the blade. The alga attaches to the substratum by means of root-like formations.

Does the plant have any uses?

It is used for human consumption. It is essentially a staple of the Korean diet and is also widely consumed in Japan.

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