The plants, which had reached a height of around 80cm (two and a
half feet) before being spotted at the weekend, were found in
vegetable patches located in the exercise courtyard of the
Saint-Martin-de-Re prison in the west of France, Christophe
Beaulieu, a regional official of the prison officers' union, told
AFP.
"When you don't know what you are looking for it is easy to
confuse them with other plants," Beaulieu said.