Baikal Hogweed, a highly toxic plant, possibly confirmed in Japan for the first time? The shocking discovery of the "world's most dangerous" invasive species on the Hokkaido University campus

Table of Contents

1. Introduction

2. What is Giant Hogweed?

3. Distribution and Damage Cases Overseas

4. Reasons for Unconfirmed Presence in Japan

5. Discovery at Hokkaido University

6. Why in Hokkaido? Investigating the Invasion Route

7. Health and Safety Risks and Medical Costs

8. Impact on Environment and Agriculture

9. Domestic and International Regulations and Control Measures

10. Initial Response in Hokkaido and Future Challenges

11. Advice for Foreign Tourists and Residents

12. Conclusion—Preventing the "Unnoticed Spread of Risk"
    
    

1. Introduction

In late June, Sapporo welcomes tourists with fresh greenery and a refreshing breeze. However, in 2025, the discovery of Giant Hogweed (Heracleum mantegazzianum), known as "the world's most dangerous plant," on the Hokkaido University campus brought tension to the otherwise peaceful campus.fnn.jp

2. What is Giant Hogweed?

A perennial plant of the Apiaceae family, characterized by white umbel flowers over 2-4 meters tall and 80 cm in diameter. The sap contains furanocoumarins, which react with ultraviolet light to cause phytophotodermatitis, damaging skin cells.rhs.org.uken.wikipedia.org

3. Distribution and Damage Cases Overseas

Introduced to the UK in the 19th century as an ornamental plant, it quickly escaped. It now spreads across Europe and the eastern coast of North America, causing burn incidents significant enough to crowd emergency rooms every summer. In the UK, the cost of controlling invasive species along riverbanks reaches tens of millions of pounds annually.rhs.org.uk

4. Reasons for Unconfirmed Presence in Japan

(1) No records of the species in Japan's planting history
(2) Climatic conditions unsuitable for reproduction
(3) Difficulty in identification—misidentification with native Angelica species
These factors combined left no trace in administrative databases. However, recent increases in average temperatures and international logistics have heightened the potential invasion risk.asahi.com

5. Discovery at Hokkaido University

On June 24, 2025, a student posted about an "unfamiliar large Apiaceae plant" on social media. Faculty confirmed it, and on the 25th, announced it on campus and decided on access restrictions.hokudai.ac.jp
The Hokkaido Prefectural Government's Natural Environment Bureau also began on-site investigations and indicated that removal and transport would be withheld until identification was complete.pref.hokkaido.lg.jp

6. Why in Hokkaido? Investigating the Invasion Route

1. Smuggling and personal import of ornamental seeds—Exotic gardening enthusiasts obtaining and planting via online shopping

2. Seed contamination in cargo ship containers—Arriving from the Russian Far East route to Sapporo Port and moving with soil

3. Escape of outdoor practice samples—Researchers bringing back Caucasus plants, escaping from greenhouses

4. Changes in climatic conditions—Rising summer temperatures and Sapporo's precipitation patterns enabling germination and overwintering
   
   

These factors likely combined to create a "survivor."

7. Health and Safety Risks and Medical Costs

Giant Hogweed sap on skin→UV exposure within 30 minutes→redness, blisters, pigmentation. Symptoms may persist for months, with severe cases requiring skin graft surgery. In the U.S., hundreds of burn incidents are reported annually, with estimated average medical costs of about $3,000 per case. If similar incidents occur in Hokkaido, there are concerns about the impact on travel insurance for visiting tourists and municipal medical expenses.en.wikipedia.org

8. Impact on Environment and Agriculture

Forms dense colonies, displacing native plants. Its shallow root system can cause erosion of riverbanks, increasing flood risks. In pastures, livestock avoid eating it, reducing forage yield and impacting farmers' economies. Overseas, millions of dollars are spent annually on herbicide application and mechanical cutting.

9. Domestic and International Regulations and Control Measures

UK: Cultivation and movement banned under the 1981 Wildlife and Countryside Act.
US: Interstate transport restricted under the Federal Noxious Weed Act.
Japan: Not designated under the Invasive Alien Species Act, but the Ministry of the Environment is considering emergency designation. Hokkaido plans to temporarily add it as a "species of concern" under local ordinance.pref.hokkaido.lg.jp

10. Initial Response in Hokkaido and Future Challenges

• Fence Installation: Temporary fences 1.8 meters high around the campus perimeter

• Multilingual Posters: Warnings in Japanese, English, Chinese, and Korean

• DNA Barcoding: Experts collecting leaf samples to expedite species identification

• Seed Bank Survey: Measuring seed density in surrounding soil

• Long-term Monitoring: Plan to observe germination status over five years
  
  
  

Challenges include coordination among landowners if spread outside the campus and minimizing non-target biological impacts from herbicide use.hokudai.ac.jp

11. Advice for Foreign Tourists and Residents

1. Use Telephoto for Photography—Avoid close-up shots

2. Be Aware of Misidentification—Similar in appearance to native Angelica and Ezo-nyu

3. If Contact Occurs—Wash immediately with soap and cold water, avoid direct sunlight for 48 hours

4. Choosing Medical Facilities—Check the list of dermatologists with English support in advance

5. Social Media Sharing—Share discovery locations with vague geotags to prevent imitation harvesting
   
   
   
   

12. Conclusion—Preventing the "Unnoticed Spread of Risk"

The discovery of Giant Hogweed in Japan indicates that the risk of invasive species can extend to academic and tourist centers. Early detection, information sharing, multilingual support, and behavioral changes among local residents and foreign tourists are key. The swift response of Hokkaido University and the government is commendable, but without follow-up investigations and legal measures, the "nightmare of proliferation" seen in North America and Europe could be repeated.

In addressing the global issue of invasive species, each of us must recognize that we stand on the "front line."

List of Reference Articles

• FNN Prime Online "Do Not Touch" More than 10 Highly Toxic Plants Unconfirmed in Japan Found on Hokkaido University Campus (June 25, 2025)fnn.jp

• Asahi Shimbun Digital Dangerous Plant "Giant Hogweed" That Causes Skin Burns Possibly Growing at Hokkaido University (June 26, 2025)asahi.com

• Hokkaido University Official Site "On the Growth of Plants Suspected of Toxicity" (June 26, 2025)hokudai.ac.jp

• Hokkaido Environmental and Lifestyle Department Natural Environment Bureau "On the Growth of Plants Suspected of Toxicity" (June 26, 2025)pref.hokkaido.lg.jp

• RHS Gardening "Giant Hogweed" Information Sheet (Revised 2024)rhs.org.uk

• Wikipedia "Heracleum mantegazzianum" Latest Edition (Updated June 2025)en.wikipedia.org