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Fall 2017
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Death by pitcher plant
Death by pitcher plant

Carnivorous Plants

The leafy, man-eating star of “Little Shop of Horrors,” Audrey Junior, was alleged to be a cross between a Venus’ flytrap and a butterwort, germinated in the coronal glow of the total eclipse of the sun. Strangely enough, if this were even a remote possibility, it would not be Skid Row but the coastal Carolinas that would spawn such a mythical plant-beast, for this is the native range of many types of carnivorous plants. The Lowcountry and Grand Strand are famous for hospitality, yet it is patches of dry, inhospitable, nutrient-poor South Carolina soil that produce these genus-bending floras.

“If you are a plant and you can do one thing in nature just a little different from everything else, like being able to live in dry mineral-deficient soil, your chances for survival are much better,” said naturalist and Old Santee Canal Park Director Brad Sale. “So these plants replaced the minerals absent from the soils with minerals from insects.” 

Most plants use photosynthesis to turn chlorophyll, sunlight and water into sugar, but plants still need minerals to convert the sugars into fats, proteins and nucleic acid compounds the plant can use for food. Without those minerals, most plants would wither and die. However, our carnivorous plant friends are able to thrive in soil where other plants simply cannot. They improvised, adapted and nibbled out, if you will, a niche where they thrive.

And many of them do indeed thrive and hospitably entertain visitors at Santee Cooper’s Old Santee Canal Park. Pitcher plants, bladderworts and others claim their space among the native vegetation by adapting to their Lowcountry surroundings.

These adaptations came in the form of specialized leaves that form traps. These plants are divided into groups according to the type of trap they deploy: 

  • Pitfall traps of pitcher plants are leaves folded to make deep, slippery pools filled with nectar and laced with digestive enzymes. In essence, prey steps over the edge of the leaves and slides into the trap.

  • Flypaper, or sticky or adhesive traps, deployed by sundews and butterworts are leaves covered in stalked glands that exude a sweet sticky mucilage.
  • Suction traps, unique to the aquatic bladderworts, are highly modified leaves in the shape of a bladder with a hinged door lined with trigger hairs.
  • Snap traps of the Venus’ flytrap and waterwheel plant are hinged leaves that snap shut when trigger hairs are touched.
  • Lobster-pot traps, also called eel traps, used by corkscrew plants are twisted tubular channels lined with hairs and glands. It’s easy for prey to walk into the hair-lined tubes, but nearly impossible for them to walk out. These plants are only found in Central and South America, and Africa.
Pitcher plant illustrations

Pitcher Plants

Pitcher plants are the most common carnivorous plant in coastal South Carolina. The iconic cluster of  pitcher-shaped leaves you see above ground is only a part of the plant. They sprout from an underground stem called a rhizome, an excellent survival strat-egy in fire prone areas. The main body of the plant remains below ground and out of harm’s way, allowing it to seize the advantage and quickly sprout anew following fires.

“Think of the palm of your hand as a rhizome, and the upturned fingers as the leaves of the plant we see,” explained Sale. “What appears to be a cluster of plants is really a single plant, growing from one rhizome.”

Before the specialized pitchers emerge, the plants send out blooms on long stems. One species produces a beautiful yellow flower as big as a fist while others create more delicate, deep-purple blooms. For all, the strategy is to attract bees – not to trap and digest them, at least not yet – that carry the pollen from other individual plants. Flowers have both female and male parts and the goal is for each plant to be fertilized by a different plant.

Genetic diversity is key to unlocking adaptations in changing environments. The flower is cleverly built so that the bee or other pollinator enters to brush up against the female stigma, depositing pollen grains from a neighbor as it enters the bloom in search of nectar. After a sticky sip, the bee continues on its one-way journey, brushing up against the stamen and collecting pollen grains to deposit on the next pitcher plant bloom on its path.

After the flowers fade, the pitchers use color and nectar-producing glands called nectaries to lure insects into their irresistible trap. The above graphic shows the process.

There are several species of pitchers plants native to coastal South Carolina including:

  • Yellow trumpet pitcher plant
  • Hooded or dwarf pitcher plant  
  • Sweet pitcher plants (which are smaller and smell better)  
  • Purple pitcher plants (also known as frog’s breeches and hunter’s horn)

Flypaper Traps

Sundews and butterworts are our native examples of flypaper traps.

Sundews get their name from the gleaming, dew-like glands that look like tipping tentacles jutting out from the main stem. These are highly adaptable plants, found on every continent except Antarctica. Insects are attracted to the plant’s sweet and sticky, mucilaginous secretions. Upon landing, the insect sticks fast. In the struggle to free itself, it is entangled in the surrounding tentacles and the sundew’s leaf  slowly closes around the victim. Sundews have sequentially blooming flowers along a shared stem. As one blooms and closes, the next will bloom and close and so on. 

Butterworts were believed to have magical powers, and farmers would rub the juice of the leaves onto milk cows’ udders to make their butter better.  Smaller than sundews, they also have leaves covered with mucilaginous glands on much shorter stalks hugging closer to the leaves. When an insect comes in contact with the leaf, it sticks fast and specialized glands on the leaf surface release digestive enzymes that make short work of the prey.

Venus’ flytrap

Suction or Bladder Traps

Bladderworts are a floating group of aquatic plants boasting more than 225 species worldwide. They all sport highly modified round leaves, or stolons, largely regarded as the most sophisticated trapping mechanism of any carnivorous plant. To set the trap, the water in the bladder leaves is pulled back into the stem, flattening the bladders and creating a vacuum. When prey contacts a trigger hair near the bladder door, it springs the trap, and the plant sucks in prey and surrounding water in as little as 1/50th of a second. The trapped prey is generally microscopic, like protozoa. Once caught, they are then bathed in digestive secretions. Bladderworts are found in fresh and brackish water all over coastal South Carolina including in Old Santee Canal Park.

Snap traps

The “rock stars” of carnivorous plants have to be the Venus’ flytraps. They deploy an active trap, meaning they actually have to move to entrap the insect. Venus’ flytraps are very small and closely hug the ground. They are highly specialized to survive in dry, nutrient-deficient soil.

When they first emerge, they are completely green. As they grow, the pads, or “mouth” where the plant produces digestive enzymes, begin to turn red. From these pads emanate three trigger hairs.  If a single hair is touched more than once in a quick secession or if more than one of these hairs is touched, the trap is sprung and closes around the hapless visitor.

It’s all done without the aid of a brain or muscles. It’s the magic of water pressure or hydraulics. The inside of the trap is comprised of densely packed cells. When tripped, the cells are triggered to fill with water. As the cells expand, the trap closes, and you know the rest.

If an insect escapes or if the trap misfires, the plant senses it’s been skunked. It reabsorbs the water and the flytrap reopens, ready to try again. Each trap is good for about 10 closures before the leaf dies and the plant grows another. The only places in the world flytraps occur naturally are within a 100-mile radius of Wilmington, N.C.

“The Venus’ flytrap doesn’t compete well with other plant species. It grows low to the ground and finds itself in the shadow of taller plants and robbed of life-giving sunlight,” said Parker Hill, Santee Cooper’s supervisor of right of way management. Santee Cooper controls undesirable vegetation under transmission lines in the Lewis Ocean Bays Heritage Preserve in Horry County, a place where Venus’ flytraps thrive.

To help protect the flytrap’s place in the ecosystem, Santee Cooper joined forces with Coastal Carolina University in 2004 to study the impact of our vegetation management practices in rights of way that cross Lewis Ocean Bays Heritage Preserve.

“Today we employ selective spraying in those areas, which promotes the flytraps,” Hill said.

In the end, humans have nothing to fear from these plants. The plants, however, have plenty to fear from us. Human intrusion and natural systems modifications, like fire suppression, are the biggest threat to continued survival of carnivorous plants. Habitat loss from land clearing, agriculture, the illegal collection of wild plants, pollution and incautious herbicide application   all pose a considerable threat.  In the end, it’s best we embrace the words of Charles Darwin: 

"The love for all creatures is the most noble attribute of man."