He said that killing some of the millions of slugs that infest gardens every year was the "nasty side" of gardening that people did not want to talk about.
As part of a project looking at the history of the British love of gardens, Ginn found that most people felt ashamed of doing so. "Killing is reasonable and unavoidable for gardeners," he insisted. "Killing slugs, squirrels and rabbits is ethically defensible. It is more of a question of how you do it.
"If gardeners were upfront about how they kill pests and learnt from the likes of Hugh Fearnley Whittingstall, it would make things clearer."
On the 50 London gardeners he surveyed, Ginn added: "Younger people who were greener were more confused, even if they used environmentally friendly ways of killing slugs, because they felt that they were not supposed to kill stuff.
"Gardeners should be proud rather than trying to hide it. The main thing is that it is done for a specific purpose to protect a certain kind of plant."