Security cameras will be installed in the Royal Botanic Gardens in a bid to strike back at tree vandals and plant thieves.

Gardens chief executive Tim Entwisle said it was sad but necessary to place three cameras, from next month, in the grounds of Melbourne's green oasis after a spate of theft and vandalism.

Botanic Gardens chief Tim Entwisle at the Montezuma bald cypress, which was attacked by vandals. Credit:Penny Stephens

The cameras won't be trained on lovers on the lawns or children feeding the swans. They will focus on the Separation tree, the arid garden and the tropical glasshouse (the latter camera possibly inside).

If the attacks continue Professor Entwisle will consider night sensor lights and more cameras. He said cameras ''detract, I think, from the tranquillity and ambience of the place. But there are only a few of them, in key spots. It's unfortunate we have to do it but I think it's a very measured response.''