A Hamilton thief who felt "a bit of a prick" after being caught stealing a cactus could have been looking for a natural high to kill the pain, experts on the plant say.

Police came across the prickly theft outside the The Switched on Gardener in Te Rapa on Sunday night when a neighbour rang them to say they had seen two men acting suspiciously.

Officers found two men cutting up a cactus into segments outside the premises, with one shaving the prickly spines off with a knife.

When questioned about what they were doing the man said he had "felt a bit of a prick" so was removing the spines to make the segments easier to carry.

The pair were arrested and charged with theft.

Garden centre owners spoken to by the Times were not aware of cactus thefts being carried out in the city, but were familiar with what the pair were trying to do.

One Hamilton garden centre staff member, who did not want to be named, said she had been approached in the past by people wanting to buy cactus and boil it up for a "high".

Associate Professor Merilyn Manley-Harris, of the chemistry department at Waikato University, said the stolen cactus looked strikingly familiar to the Echinopsis pachanoi, the San Pedro cactus, that contains the hallucinogenic mescaline.

The cactus held a "chemical cocktail of psychedelic agents" that if taken in the wrong dosage could kill, Ms Manley-Harris said.

"If you muck around with it this sort of thing can kill you."

Bruce Sanson of The Plant Place in Hamilton said although there was a spate of cacti thefts in the city several years ago he was not aware of any recent incidents.

Waikato police spokesman Andrew McAlley said cactus thefts had not been prevalent in the area recently but it was not unusual.

However, police would not be surprised if more people who had had cacti stolen came forward after publicising the latest theft.

"It could be that this is occurring but people haven't thought of it as serious.

"But the police stance is that if any offending happens we need to know about it so we can at least put it on our radar. It may not lead to an arrest but it helps us build up a pattern of offending."

CACTUS DANGERS

Some species contain mescaline, a naturally occurring hallucinogenic.

Taken in the wrong dosage, mescaline can kill.

The mescaline cactus is commonly cut up and boiled as a drink.

Mescalin can be dried into a powder, and is a Class A drug in Britain.