Another Mouth to Feed: Exotic, Fascinating and Deadly Carnivorous Plants

Most plants are docile and passive, minding their own business and content to grow in the ground or their containers with just reasonable care. 

Carnivorous plants defy the stereotype. 

Like sirens luring sailors to their rocky deaths, Venus flytraps, sundews, bladderworts, and others attract prey to their doom not with a song but with clever strategies, sometimes in combination. Sure, some carnivorous plants emit a sweet floral scent to entice an unwary insect or other small invertebrate.  But most are craftier than that.

Consider, for example, the pitcher plant, whose modified leaves form what’s known as a pitfall trap. These tricksters draw victims with a one-two punch, then kill off future generations. By pairing reflective spots that look like water with the tell-tale odor of decomposing organic matter, pitcher plants look like a great place for insect breeding. But when adult gnats and flies lay their eggs on the plant’s pitchers, they fall in and are trapped by a waxy substance.

Or what about sundews? They produce glistening drops of what innocently look like morning dew but turn out to be sticky substances that glue their prey’s feet in place.

As for the iconic Venus flytrap — the best known carnivorous plant, with the possible exception of Audrey from Little Shop of Horrors — its vibrant colors are impossible for some arthropods to ignore. When prey catch on its jaw-like leaf, downward-pointing trigger hairs keep them from crawling back out. The trigger hairs cause the plant’s “jaws” to close, trapping the prey. Like other carnivorous plants, digestive enzymes finish them off. The leaf will open up again in about 10 days, ready for another meal. 

This is the stuff of a spy thriller, right? It’s easy to see why people are so fascinated with these somewhat nefarious tropical plants, even though they’re only doing what comes naturally.

Not the same family “tree”

Though their trapping mechanisms differ, carnivorous plants share genetic similarities in their ability to produce digestive enzymes and absorb nutrients, which might make you think they’re in the same family.  

The truth is they aren’t, and the reason has to do with heredity and adaptation. 

Most carnivorous plants have ordinary, non-carnivorous ancestors. Their carnivory evolved independently multiple times in different plant lineages but always for the same purpose: to survive in nutrient-poor environments that lack the nitrogen and phosphorous crucial to plant growth. 

That’s why Venus flytraps and sundews belong to the Droseraceae family, bladderworts are in the Lentibulariaceae family, and pitcher plants belong to several families, including Nepenthaceae and Sarraceniaceae.

What’s on the menu?

Environmental adaptation is also behind the various diets different carnivorous plants prefer. They target the “food” sources most abundant in their habitat. And even if they capture an insect, they don’t necessarily digest it — some are used for other purposes, such as pollination or waste decomposition.

In general, though Venus flytraps prefer ants, flies, spiders, and other small crawling insects, while pitcher plants, depending on their size, target everything from ants, mosquitoes, and spiders to small frogs and rodents. For sundews and bladderworts, the primary prey are gnats, midges, fruit flies, and mosquitoes.

This begs the question: If you’re growing carnivorous plants in the comfort of your presumably insect and rodent-free home, how do you supply the nutrients they need?

Basically, there are two choices. If you’re not squeamish, you can offer small insects like flies, gnats, or bloodworms once every few weeks during the growing season (spring and summer). Alternatively, you can use commercially available carnivorous plant food, typically freeze-dried bloodworms or other insect parts.

Aside from watching their diet, caring for carnivorous plants is no more difficult than other plants. Remember to:

• Choose a pot with drainage holes to prevent waterlogging. Most hobbyists use plastic pots for their carnivorous plants.
• Feed only as needed. Carnivorous plants can survive for extended periods without consuming insects, especially if they are receiving adequate sunlight and water.
• Place your plant where it will receive six to eight hours of bright, indirect sunlight each day. 
• Avoid watering with tap water; the plants are sensitive to the minerals in it. Instead, use distilled water, rainwater, or water that has been sitting out for 24 hours to allow chlorine to evaporate. Keep the soil consistently moist but not soggy. Cut back on watering during winter dormancy.

Carnivorous plants are generally less susceptible to pests and diseases compared to other houseplants, although fungal gnats and mealybugs can be a problem.

Admittedly, carnivorous plants aren’t for everyone. But if you’ve got an appetite for something that’s surprisingly beautiful (some would say drop-dead gorgeous) and probably more intriguing than your pothos — and you don’t mind having another “mouth” to feed — they may be a great addition to your plant collection.