The unnamed gardener grew strange carnivorous plants in his back garden. He seemed to be some kind of plant-monster himself.
The Richie Rich/Scooby-Doo Show
The vegetable-like man hired Shaggy Rogers, Scooby-Doo, and Scrappy-Doo (working as the Three S Gardening Services) to take care of the plants, but he really meant for them to become plant-food. (Hothouse Scooby)