A game where people climb trees to drink alcohol is causing trouble in the Dunedin Botanic Gardens, with glass, litter and vomit often left behind.



In the game, called ''possum'', a group of people drink alcohol, usually a 24-pack of beer, while up a tree.

The first one to fall out from drunkenness loses the game.



Dunedin City Council gardens and cemeteries team leader Alan Matchett said people, believed mostly to be students, played the game at the gardens in the afternoons and early evenings, during the week and at weekends.



Staff were fed up with the mess left behind, which included glass, food scraps and cans.



"It's been occurring fairly regularly for the last two or three years. We don't usually see them, but police and Otago University campus watch staff have had to move people on from the park and told them to clean up their mess," Matchett said.



"What they drink has to come out again, so they do throw up and urinate from the trees. Obviously, it's not nice to have that left behind."



He said staff were concerned about the safety of people falling from trees as well as the potential damage caused to the trees, some of which were more than 100 years old.



''It's obviously not an activity we want to encourage and it's not nice for other users of the gardens. As a park manager, I just think it's a bit pointless," Matchett said.



A former Otago University student, who did not want his name published, said he had played the game, in his first year, at the gardens of his hall of residence.



"I climbed a tree, drank a box [of beer] and then climbed back down and went to town,'' he said.

''There were about four of five people up other trees ... Drinking challenges were all the rage back then."



He did not fall out of his tree and could not remember if anyone fell out of any other trees, but the game was common.



The game appeared to have not yet spread to Christchurch.



A Christchurch City Council spokeswoman said the council had not had problems in any council-owned garden.



"This new game was news to our greenspace staff," she said.



University of Canterbury Students' Association president Erin Jackson said she had heard of the game, but she did not think it was a problem in Christchurch.



"From being a student, I've heard it discussed, but I've never actually seen anyone do it,'' she said.

''We certainly haven't had it come up as an issue here.

''We have a good relationship with the community over students' drinking, so I think if it was a serious problem here it would have come to our attention."



Jackson said perhaps it was because Christchurch did not have many suitable trees.



"I think our city is laid out a little differently to Dunedin,'' she said. ''I don't even know where people would go to do it."