Mr Matchett said cacti was once used in North American Indian ceremonial rituals.
Sergeant Steve Aitken, of Dunedin, said under New Zealand law mescaline was considered a class A drug.
No drug species are on public display in the glasshouse.
However, Mr Matchett said the garden did have several examples of cacti which could produce class A drugs, but they were kept at an undisclosed secure location.
The security camera was installed after several break-ins during which cacti were damaged or stolen, Mr Matchett said.
The camera had since been replaced.
He declined to say how many times cacti had been stolen from the garden in the past, but said as a result of those thefts, some cacti specimens were no longer kept on public display.
''We try not to grow certain cacti on display if they are susceptible to theft.''
He said there were other drug-producing plants in the garden, such as poppies, but declined to say what or where those plants were.
''There are some that are definitely capable of producing class A drugs.''
Police investigations into the theft of the security camera are continuing.