Meat-Eating Plants

"I want people to get passionate about plants," says Lisa Van Cleef about a new exhibit at the San Francisco Conservatory of Flowers. "Everybody gets excited about the zoo and animals, but once you start looking at plants you find they have a lot going on, too!"

Especially the carnivores, or meat eaters, that use the sneakiest of tricks to trap their insect dinners. Take bladderworts, for example. They appear so small and delicate growing in a quiet pond. But these are the fastest-known killers of the plant kingdom, able to suck in unsuspecting mosquito larvae in 1/50 of a second using a trap door!

Once the trap door closes on the victim, digestive enzymes similar to those in the human stomach slowly consume the insect. When dinner is over, the plant ejects the remains and is ready to trap again.

Carnivorous plants grow in places with soil that doesn't offer much food value. "You and I could take a vitamin pill," says Van Cleef. "But these amazing plants have had to evolve over thousands of years, developing insect traps to get their nutritional needs met. Just look at all they've done in the fight to survive."

The traps can be well-disguised to fool the eye, like pitcher plants, which get their name because they look like beautiful pitchers full of nectar.

The Asian pitcher plant, for example, has a brightly colored rim and an enticing half-closed lid. Curious insects are tempted to come close and take a sip, then slide down the slippery slope to their deaths.

Hair-like growths along the pitcher walls ensure that nothing can scramble out, and the digestive enzymes can get to work. A tiny insect called a midge might be digested in a few hours, but a fly takes a couple of days.

Some of these pitchers are large enough to hold two gallons (7.5 liters). Carnivorous plants only eat people in science fiction movies, but once in a while a small lizard, rodent, or bird will discover that a pitcher plant isn't a good place to get a drink.

Other plants have found different ways to grab a bite. Sundews and butterworts snag snacks with flypaper-like stickiness, while the Venus flytrap snaps shut on its victims.

Carnivorous plants grow mostly in wet areas, from sea level to the mountains. They may seem exotic, but if you live in the United States, you don't have to travel to faraway lands to see some. North America has more carnivorous plant genera than any other continent.

If you can't travel to the exhibit in San Francisco, check out a carnivorous plant guidebook from your local library, and you may discover some growing in your neck of the woods!

Fast Facts

  • The cobra lily (Darlingtonia californica) has clear cells on top of its pitcherlike trap that work like a skylight. Think about it: Would you rather enter a dark cave, or a light one?
  • Some pitcher plants (Nepethenes) trap frogs, and when the frogs are digested, all that remains are little matching frog slippers since the skin on frogs' feet resists digestion.
  • Most Nepethenes have two kinds of pitchers, some low to the ground to attract crawling insects, and some higher up to catch those that fly.