Common names: wakame; Japanese kelp; Asian seaweed
Undaria pinnatifida (wakame) is an annual algae (family Alariaceae) first recorded in several estuaries in California in 2000. Wakame is native to Japan, where it is consumed for its food value and as a nutritional supplement. In California, wakame usually cannot compete with native perennial brown algae, but it may colonize estuaries rapidly if native algae are not present. Hence, wakame occurs in high densities only in recently disturbed areas. Although it does not appear to have serious impacts in California, it has been a very serious invader in New Zealand.
High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.
A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
* – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
-* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.
Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
Weed Management Notes
No Weed RIC Management Notes are available for this species. Check for information on other species in the genus on the Weed RIC site.
Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.
Calflora - Distribution map and records of this species in California.
CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
EDDMapS - Distribution of this species in North America.
Additional photos
Undaria pinnatifida (wakame) sporophyll and base of mature frond. Photo: Joe DiTomasoUndaria pinnatifida (wakame) young frond (left) and sporophyll frond (right). Photo: Joe DiTomaso
