Carnivorous plants are curious manifestations that turn Mother Nature on her ear.
Typically, the animal kingdom feeds on the plant kingdom, but these plants of prey reverse the food chain.
Using ingenious techniques ranging from flypaper and pitfalls to suction and spring-loaded traps, carnivorous plants lure, imprison and devour not only insects, but sometimes small fish, tadpoles, frogs, lizards, birds and even an occasional rabbit or rat.
The flesh-eating adaptation compensates for soils lacking nutrients.
“It’s a great story in evolution,” says Joe Tomocik, curator of water gardens at Denver Botanic Gardens.
Charles Darwin, in fact, studied the bloodcurdling habits of these wildflowers and in 1870, published a classic work titled “Insectivorous Plants.” When the plants later were found to feast on more than bugs, the name was changed to carnivorous plants.
At Denver Botanic Gardens, Venus fly traps are one of several varieties of carnivorous plants on display in an area known as Fly Trap Feast.
“We arranged these containers so that people can get in here and walk around and get a close look,” Tomocik said. “Some places are like museums with ‘Do Not Touch’ signs. I say, ‘Do touch!”‘
In fact, two touches to the three sensitive trigger hairs inside a Venus flytrap activate the mechanism that closes the plant on its prey. Baiting prospective dinner with nectar, the plant encloses victims in a cage. When an insect struggles, the trigger hairs send electrical impulses that close the trap further. The plant then fills with liquid digestive enzymes, drowning the victim and then dissolving it over several days.
Though Venus flytraps seem like they should hail from some exotic jungle or possibly another planet, they actually are native to North and South Carolina. Looking something like a green clam shell with teeth, the plant’s common name is a misnomer since Venus fly traps tend to live on ants.
On display at the gardens with the flytraps are pitcher plants. In the Sarracenia genus, these plants form vessels able to hold liquid, as their common name implies. In this case, the pitchers hold digestive fluids. Baiting prey with secretions of nectar outside the trap, the plants entice bugs inside, where downward pointing hairs cause the insect to slide into the pitcher and the digestive juices.
Other carnivorous plants include sundews and bladderworts, some of which are native to Colorado.
Sundews belong to the family of Drosera – the name means “glistening in the sun.” In Tomocik’s bailiwick of the Denver Botanic Gardens greenhouse, sundews thrive in hanging pots. Amid the hairy pinking tentacles are unfortunate flies, gnats and even sizable dragonflies in various stages of decomposition.
In addition to sticky glands, the plant’s tendrils move to snare their prey. Once prey sticks to the gluey substance, the plant enfolds the victim, curving its tentacles in to “eat.”
Aside from shock value and possible organic pesticide function, carnivorous plants have medicinal applications. Extracts or teas from the plants have been used to treat everything from sunburn to morning sickness to corns and warts to diseases like asthma and tuberculosis.
A 15-year-old George Washington High School student, Michael Chan, is one of Tomocik’s most valued volunteers. Chan’s interest in carnivorous plants was aroused when he purchased a pitcher plant from a hardware store.
“I wanted to buy it for fun,” Chan said. “I saw it when I was younger on the Discovery Channel, and I thought it was such a fascinating plant. My collection is a lot larger now.”
And so is his interest. Chan is conducting research into the antibiotic properties of extracts from carnivorous plants.
“In one of the books I was using to learn how to grow carnivorous plants, I saw that butterwort was used by farmers to rub on open wounds of cattle to promote healing,” Chan said. “There’s some kind of an antiseptic on them, so I figured it would be interesting to try an experiment with plant-derived antibiotics from carnivorous plants.”
More often cultivated as a macabre novelty than as a curative, carnivorous plans also have design value, Tomocik says.
“These containers look nice from afar, and when you come up close, there are big stories.”
In the greenhouse, he propagates butterworts – attractive plants with thick, succulent-like leaves coated with a sticky substance. They produce delicate, five-petaled, hot-pink flowers.
Admiring an elegant, yellow pitcher plant with elongated cornets, another with a lattice of colored veins, Tomocik says, “People underestimate the ornamental value of carnivorous plants.”
However, interest in these lovely and deadly plants is growing. And though one might wonder if they’re more like a pet than a plant, they do not require endless mollycoddling.
“They’re slow growing and slow to reproduce, but they’re not hard to care for,” Tomocik said.
The plants do require moisture, and most books recommend using reverse osmosis (RO) water or distilled water.
“When we haven’t used RO water, we haven’t killed them, so in my estimation, it’s not necessary,” Tomocik said.
As an insurance policy, in the greenhouse he sets the plants’ containers in half an inch of water, allowing a capillary process to draw up moisture.
“They seem like they’re jungle plants, but they like lots of sun,” Tomocik said. “The roots are delicate. They can’t take heavy soil. Use something soft like peat with sand – and no fertilizer.”
In other words, they’ll fix their own meals.
Carnivorous plants can be grown outdoors in Colorado’s Zone 5.
“They’re fairly cold hardy, so you can keep them outside as long as they don’t dry out,” Chan said. “Dry wind can hurt them. I recommend putting plastic over them, mulching them or bringing them in to an unheated garage, next to a windowsill, preferably, in the winter.”
For would-be carnivorous plant collectors, Chan recommends Cobraplant.com and californiacarnivores.com as online sources. Tomocik touts a carnivorous plant reference book by Peter D’Amato aptly titled “The Savage Garden.”
