The Duchess of Northumberland will be allowed to grow drugs, including cannabis and opium, at Alnwick Gardens.
The Home Office has approved a licence for the Alnwick Garden charity to grow the plants for educational purposes.
Poisonous foxglove, tobacco and wild
lettuce, which can be used as a tranquilliser, will also be grown.
Visitors to the walled garden, which is designed to provoke open and relaxed discussion about drugs issues, will be escorted by marshals.
The special Poison Garden has been designed by Belgian Peter Virtz and will open within weeks, although many of the plants will not be growing until the spring.
Magic mushrooms and more than 50 dangerous plants will also be included in the collection.
Alison Hamer, Alnwick Garden's learning development manager, said: "The subjects of drugs, alcohol, tobacco and medicines, and their use are very emotive ones.
"For many people, the thought of talking about drugs to younger family members or friends is quite scary.
"However, the Poison Garden provides an innovative opportunity for us to deliver, in a relaxed atmosphere, simple information on drugs and drugs issues to a section of the general public that can be hard to reach."