A non-native komakusa plant is seen on Mount Tarumae in Tomakomai, Hokkaido, July 14, 2026. (Mainichi/Daiki Kobayashi)
SAPPORO — A non-native plant species brought in by climbers and others is taking root on mountains in Hokkaido, creating a situation that could affect ecosystems. At the same time, there are voices both for and against eradicating the invasive plants.
In mid-July, in slanting rain, seven people — officials from the Ministry of the Environment and volunteers — gathered on the outer rim of Mount Tarumae, a 1,041-meter peak in Shikotsu-Toya National Park, south of Sapporo. On a slope near the hiking trail, a large colony of “komakusa,” sometimes called the “queen of alpine plants,” spread across about 5,000 square meters.
Komakusa does not naturally grow on Mount Tarumae. In some places, there was so much of it that it was difficult to find a place to step. At first glance, it looked like a beautiful alpine flower field, but one volunteer described it this way:
“It’s a dystopia.”
The seven people picked komakusa flowers and put them into plastic bags. When they tore apart the collected flowers, the insides were found packed with round black seeds 1 to 2 millimeters in diameter. A ministry official who led the activity explained, “There are too many plants to remove completely. We are picking the flowers so the seeds don’t spread.”
Komakusa is a perennial in the poppy family. It grows in clusters in alpine zones from Japan’s central Chubu region northward, producing pink flowers and, rarely, white ones. It is designated as near threatened on Hokkaido’s Red List, and within Hokkaido it occurs naturally in areas such as the Daisetsu mountain range and the Hidaka mountains, which are higher in elevation than Mount Tarumae.
Participants pluck komakusa flowers in a colony of the invasive plants on Mount Tarumae in Tomakomai, Hokkaido, July 14, 2026. (Mainichi/Daiki Kobayashi)
According to a local newspaper report from 2003, “a climber planted it in 1986.” That apparently led to its establishment on Mount Tarumae as a species introduced from another part of Japan. Since about 30 years ago, the national government, which manages the national park, and volunteers have been working to eradicate it on the grounds that it could have a negative impact on the ecosystem. But removal efforts have not kept pace, and eradication remains far out of reach.
Why did the non-native species spread this far?
Komakusa plants can be bought at gardening shops that specialize in alpine plants. They are also sold on flea market apps for several hundred yen (several dollars) per plant. They bloom around July every year and produce about 100 seeds per plant. Such factors may also be contributing to their spread.
According to Atsuro Iwasaki, head of Iwasaki-engei, which grows and sells wild plants in Kitahiroshima, Hokkaido, komakusa “is surprisingly tolerant of warm climates, and elevation has little to do with its growing conditions.”
Even in lowland areas such as Sapporo, if it is planted in a place with good drainage, it will sprout the following spring. It is highly adaptable to its environment and is very robust.
In general, domestic non-native species are considered capable of negatively affecting existing ecosystems. For example, the freshwater fish “hasu” occurs naturally in places including the Yodogawa river system, whose source is Lake Biwa in Shiga Prefecture, but it spread nationwide after mixing in with juvenile “ayu” sweetfish taken from Lake Biwa for stocking.
Hasu is designated on the national Red List as “vulnerable,” a category for species whose risk of extinction is increasing. But because of concerns that the carnivorous hasu eats native fish, it is sometimes eradicated in places beyond its original ecosystem.
Non-native species may crossbreed with closely related native organisms.
Is the komakusa that is spreading on Mount Tarumae affecting the surrounding ecosystem? The latest survey did not reveal any impact from komakusa, and a certain number of native plants that originally grew there were also confirmed. The park office said, “We cannot say that komakusa is having a negative impact on other plants.”
On the mountain, diverse plants and flowers could be observed within the komakusa colony, including alpine plants regarded as symbols of the mountain, such as “iwabukuro” and “urajirotade.” Here, it appeared that komakusa was not affecting the surrounding ecosystem.
Even so, the park office emphasized that the purpose of eradicating komakusa, which is also a rare plant, is “to preserve the original natural landscape.”
Iwasaki, who saw the komakusa colony on Mount Tarumae three years ago, made this proposal: “It’s an impressive colony compared with natural habitats in Hokkaido. If it has no impact on the ecosystem, using it for tourism could be one option.”
There is still no objective evidence that komakusa is not having a negative impact on the ecosystem. On the other hand, changes in the environment may have created conditions in which non-native and native species can coexist. With its impact as a non-native species still unclear, komakusa’s fate hangs in the balance, as it could be eradicated.
(Japanese original by Daiki Kobayashi, Hokkaido News Department)