I encountered a patch of these evildoers in West Nose Creek Park. Not knowing what they were at the time, I took some photos and did some research. The plants were hard to miss, standing up to four feet tall!
- Annual or Perennial
- Reproduces by seed only (see photos below of seed pods)
- Native to Eurasia
- All parts of the plant are poisonous to animals (including humans)
- A single plant can produce up to 500,000 seeds per season
- Seeds are typically viable for up to four years
- Prefers sunny areas
West Nose Creek Park (natural area), above
I notified the City of Calgary about the weeds presence and offered my volunteer labour to help remove them. Being such a large bushy plant, I envisioned that hand removal would be quite easy with a pair of rubber gloves and garbage bags. But then what to do with the remains to prevent further spread?
I received no response from the City, but a few weeks later the plants had been removed and the City had done some spot spraying for invasive weeds, primarily Yellow Clematis (Clematis tangutica) which has really taken hold in the park. I'll be keeping my eye out for their potential return.
 Black Henbane - Alberta Invasive Plants Council