"We may be surrounded by many more murderous plants than we think," said botanist Mark Chase, Keeper of the Jodrell Laboratory at the Royal Botanic Gardens at Kew in England.

That's according to a new review on carnivorous plants which suggests that a number of commonplace, garden-variety plants like petunias and potatoes deserve to be classified as meat-eaters just like the Venus flytrap and pitcher plants.

The review looked at all the research so far on carnivorous plants and found that what constitutes carnivory in plants has historically been vague and loosely defined. While only a handful of flora directly digest the bugs they catch, a wide variety of other plants possess mechanisms which allow them to go about their murderous business in a subtler manner than their more conspicuous cousins.

For instance, petunias and potatoes have sticky hairs that trap insects, and some species of campion have the common name of 'catchfly' for the same reason. They don't immediately digest their prey, but the animals they ensnare eventually breakdown in the surrounding soil, providing nutrients that can be absorbed through the roots.

"Many commonly grown plants may turn out to be cryptic carnivores, at least by absorbing through their roots the breakdown products of the animals that they ensnare," said Chase.

At present scientists widely recognize at least six different kinds of killer plants, all of which typically kill in order to supplement their hunger for nitrogen and phosphorus in nutrient-poor habitats. Plants like petunias and potatoes are essentially doing the same thing, just in a more sinister way. Rather than devouring their prey immediately, they are using their victims' bodies as fertilizer. 

"What plants are doing is much more sophisticated than we ever imagined," Chase told Livescience. "Although animals are eating plants, plants are also eating animals. It's not just a one-way street."