Last week, police in Bedford seized what one officer termed the "biggest cannabis plant" the force had seen.
After purchasing the potted plant at a sale thinking it was a shrub, the couple planted the illicit item in their back garden and tended to it until it had reached a substantial size.
Police removed the plant and said it would be disposed of. They also confirmed the couple would face no further action.
An officer posted an image of the plant on the @bedfordlpt Twitter account, saying: "Seized today. Elderly couple bought shrub at car boot sale, tended carefully - biggest cannabis plant we had seen!!"