Lanceleaf coreopsis (Coreopsis lanceolata): https://en.wikipedia.org/wiki/Coreopsis_lanceolata
Arakawa River, Kofu-shi, Yamanashi, 5/15/2022
Lanceleaf coreopsis (Coreopsis lanceolata), locally known as Okinkeigiku, is troublesome in Yamanashi and all over Japan because of its extreme hardiness and aggressive reproductive traits. Originally introduced for ornamental and greening purposes from North America, Coreopsis lanceolata outcompetes native vegetation and harms the region’s biodiversity. Coreopsis lanceolata is legally designated as an Invasive Alien Species in Japan and the cultivation, transportation, and sale of the plant are strictly prohibited.
https://www.nilim.go.jp/english/annual/annual2011/3-4-16.pdf; https://www.nies.go.jp/biodiversity/invasive/DB/detail/80490e.html; https://www.pref.yamanashi.jp.e.aao.hp.transer.com/shizen/gairaiseibutu/ookinkeigiku.html
The plant poses a significant threat to Yamanashi’s unique ecosystems for several concrete reasons:
- Aggressive Soil Competition: Coreopsis lanceolata grows a dense foliar canopy that blocks vital understory light. This shades out and displaces native grasses and endemic riparian plants.
- High Reproductive Capacity: The plant produces thousands of seeds that can survive in the soil for years.
- Tough, Perennial Constitution: It spreads rapidly through both seeds and rhizomes. Even after rigorous cutting or mowing, the plant recovers quickly and easily.
- Disruptive to Infrastructure and Scenery: It frequently invades roadsides, riverbeds, and hiking trails, making local conservation efforts necessary to protect indigenous species from being choked out.
Because the plant has been integrated into the local pollinator community (like Halictidae, sweet bees), its seeds are easily and consistently propagated.
Several municipalities and volunteer groups across Japan are frequently forced to organize massive, labor-intensive eradication events to dispose of Coreopsis lanceolata properly.
Some examples are as follows:
TOGO SEISAKUSYO CORPORATION; We carried out eradication work on the invasive species “Coreopsis lanceolata”: https://www.togoh.co.jp/en/news/news-482
Shizuoka City conducted a simultaneous eradication campaign for Coreopsis lanceolata across eight locations to protect native plant species from this highly invasive alien species on May 26, 2026.
As one of the Corporate Social Responsibility activities, Sango Co., Ltd., based in the city of Miyoshi in Aichi Prefecture, has been involving in eradication of Coreopsis lanceolata since 2016. Sango Co., Ltd.: https://sango.jp/en/
Protect Our Island from Invasive Species! Call for Volunteers to Weed Out Lance-leaved Tickseed: https://www.oki-geopark.jp/en/news/4806/
In Yamanashi Prefecture, the cities of Nirasaki, Fuefuki, and Fujiyoshida and the towns of Hayakawa and Fujikawaguchiko and also the government of Yamanashi Prefecture have organized eradication events to dispose of Coreopsis lanceolata properly.
Also, please read the article on Invasive Plants: Lance-leaved tickseed and Kudzu: https://etsuo.tokyo/2022/06/.