Cannabis, opium poppies, magic mushrooms and coca – the source of cocaine – all feature at the centuries-old Alnwick Garden.
The Home Office granted the Alnwick Garden Trust permission to grow the plants late last year.
Poisonous foxglove, tobacco and wild lettuce, which can be used as a tranquilliser, will also be grown.
The site has been designed by Belgian Peter Virtz. More than 50 dangerous plants are included in the collection.
To highlight its hazardous nature the garden’s beds are laid in the shape of flickering flames.
Members of the public will be escorted around the walled garden by marshals.
The Duchess of Northumberland officially opened the garden with Northumbria Police chief constable Crispian Strachan.
She said: “Drugs are a major concern across the country and an emotive issue.
“The garden will offer a new avenue, outside the classroom, to get people talking about the misuse of drugs – most of which grow in nature.”