In a world of vast biological diversity, nature provides us with many marvels to explore and fascinate. These carnivorous plants have captured the imagination wildly enough to be featured in television shows and movies.
In this article from HerbSpeak, you’ll learn about several types of carnivorous plants that you might not have even known existed.
What are the Three Types of Carnivorous Plants?
There are three primary types of carnivorous plants which are organized by how their trap acts when it captures prey. These three types of carnivorous plant traps can be categorized into active, semi-active, and passive traps:
Active traps utilize motion to suck in prey, or snap closed over their prey and begin digesting them. The venus flytrap is the most popular active trap carnivorous plant, featuring trigger hairs that release an internal signal within the flytrap with each touch. If these cilia are touched in the right timeframe, the trap snaps shut over its prey.
Semi-active traps are those which use a combination of passive capture and active movement. Most notably, the sundew utilizes this type of trap, as it is passive until prey finds its way into the trap. Once caught, the semi-active trap may utilize motion to fully ensnare the prey or activate digestion.
A passive trap is one that is inactive and does not utilize movement to capture prey. These traps commonly have pitfalls or a similar type of structure to ensure their prey cannot get out once they unwittingly find their way in.
Different Types of Carnivorous Plants
Carnivorous plants are often categorized by their trap type:
- Pitfall traps
These traps are rolled leaves which form deep chambers with digestive fluids inside. Nectar and bright patterning attracts prey to the mouth of the pit, and a waxy coating encourages them to lose their footing and fall into the trap below.
- Sticky traps
As nature’s flypaper, these traps are coated in a sticky mucilage that snag insects out of the air and trap them on the surface of the plant so that it can begin digestion.
- Snap traps
Snap traps utilize rapid movement to ensnare prey and form a seal which prevents it from escaping.
- Bladder traps
These traps create a vacuum that sucks prey into a hollow, digestive tube if they accidentally bump into the plant or come too close to the opening of the bladder.
- Lobster pot traps
These traps are an open, digestive chamber that prey can enter, with inward-pointed hairs that prevent prey from leaving.
- Combination traps
These traps utilize a combination of one or more trap types, either by blending them into a single trap or in two separate functions of the plant. While this is not common, it is known to occur in certain species.
These traps are considered one of the most popular types of traps found in carnivorous plants, and it comes in a variety of shapes, sizes, and types from iconic pitcher plants to even a carnivorous bromeliad Brocchinia reducta.
These traps are typically characterized by a cauldron or tube filled with digestive fluid, which is open at the top. The sides of this plant are often waxy and slippery, making it difficult for prey to escape falling if they lose their footing at the mouth of the plant.
Pitfall traps are entirely passive, attracting insects and small mammals with bright patterning along the flower and encouraging them to climb over the top of the trap with sweet, nutritious nectar.
Most notably with Sarracenia pitcher plants, there is typically an operculum, or hood leaf, which covers the top of the trap like an umbrella, protecting the inside of the trap from rain. It is under this leaf, near the entrance of the pit’s mouth that nectar is secreted to lure prey in.
Other species, such as Heliamphora, solve rainwater overflow by evolving to have a small opening along the sides of the plant, providing an overflow drain.
In smaller pitcher plant species, small mammals attracted to these plants are positioned over the plant in such a way that they can defecate into the trap, providing it with nutrients the plant lacks.
If an insect, amphibian, or small mammal were to find its way into the large opening, it is met with the waxy leaf coating that causes it to slip further with each attempt to escape. Digestive juices sit at the bottom of the trap, waiting to start working away at fresh prey and turn it into a liquidated form that the plant can absorb.
Flypaper or Sticky Traps
Sticky traps utilize a glue-like mucilage produced on the surface of the plant, much like modern flypaper. The leaf secretes this glue through glands studded across its surface. These glands may be short and close to the surface like Pinguicula conzattii or appear as long, mobile glands or hairs like in Drosera.
In addition to a sticky mucilage, the plant may also respond with motion to further prevent prey from escaping its touch.
In Pinguicula, or butterwort, the leaf may roll over the prey to prevent it from coming free from the leaf or form a cup around its prey where digestive fluid can collect.
In Drosera, or sundew, the long, sticky hairs will entrap prey and, once the insect stimulates these hairs, the stem will begin to bend (thigmotropism) towards the touch stimulus, rolling up over its prey and trapping it in a cell of digestive hairs.
The snap trap evolved from sticky traps, and thus they share distant similarities. Only two species utilize fully active snap traps: Dionaea muscipula, the Venus flytrap, and Aldrovanda vesiculosa, the waterwheel plant. In the trap are cilia that respond to touch and generate an action potential to the central midrib. If an insect or small mammal touches two of these hairs within 20 seconds, the trap snaps shut over the animal and creates a hermetic seal, allowing the plant to begin filling the trap with digestive fluid.
Because of the great amount of energy it takes to snap these traps shut, it’s important for the plant to be able to distinguish between rain, wind, or other false stimuli can accidentally touch these cilia.
Therefore, the cilia must be touched twice between a half second and 20 seconds from the first stimulus. Each touch raises the action potential; any longer than the threshold and the trap loses “memory” of the touch. Within those 20 seconds, a second stimulus will push the action potential past its threshold, causing the snap reaction.
Insects or small mammals that struggle after the trap has shut will further tighten the seal and stimulate digestive acid.
Suction or Bladder Traps
Bladder traps are exclusive to the bladderwort genus Utricularia. These plants are well known as commonplace or keystone aquatic plants, yet not many people know that they are carnivorous. Some of these plants are semi-terrestrial, growing in waterlogged soil with anchoring stems.
This type of trap utilizes an interesting method of carnivory, utilizing hollowed sacs along the stem. These bladders may appear as dark spots or can be transparent. These bladders create a low-pressure vacuum by pumping ions out, which naturally causes water to follow through osmosis.
These hollowed bladders have small, hinged openings in terrestrial species, and long trigger hairs in aquatic species. When an insect or aquatic invertebrate agitate these trigger hairs or opening, it releases the vacuum, which sucks it into the trap. The bladder then digests its prey as it cannot leave the trap.
Lobster Pot Traps
These traps are constructed from a Y-shaped leaf, creating a chamber that is easy for prey to enter; however, once they enter it’s not so easy to leave. Cilia on the inside of the leaf point inwards, obstructing the exit from view and making it difficult to break through.
Any prey that enters the trap will find themselves trying to leave the trap by traveling downwards where they sense water movement. Unfortunately, this is towards the lower arm of the Y shape, where the digestion fluid is.
This trap type is strongly featured in Genlisea spp. plants, also known as Corkscrew plants which grow in wet or semi-aquatic environments. The tops of the Y-shaped leaves protrude just barely above ground, and the lower portion of the leaf disappears below ground. The roots give the plant its name, as they grow in a corkscrew-like fashion.
Other carnivorous plants, such as some species of Sarracenia, Nepenthes, and Darlingtonia feature attributes that are similar or reminiscent of this trap type as well.
There are many carnivorous plants that utilize a combination of more than one trap type to ensnare its prey. Most notably, Drosera glanduligera utilizes sticky traps alongside snap traps, making it a unique sight in Tasmania and Australia where it natively grows.
Hypothetically, there could be any number of trap combinations, however, this combination of snap trap and sticky traps is one of the most well-known.
More commonly, however, is the combination of pitfall and sticky traps, which is utilized by most Nepenthes that originate from Sumatra. This combination results in a sticky pitcher fluid, making it more difficult for prey to escape once they fall into the pitcher. Nepenthes jamban, N. inermis, N. dubia, and N. flava are all recorded as utilizing this combination.
How Many Carnivorous Plants Are There?
From the Venus flytrap to the Sundew, there are a lot more carnivorous plant species out there than a lot of people might think.
Currently, there are an estimated 630 carnivorous plant species known to the world, with more being discovered as we continue to explore and learn more about the plants around us.
From the carnivorous plant species we currently know, it is surprising at just how variable they are in size. The Nepenthes species captures both sides of the size spectrum:
Nepenthes argentii is a highland pitcher plant native to the Philippines. It is considered the smallest in the genus, with mature plants reaching no bigger than 25 cm (9.8”) in diameter. This plant does not appear to have a climbing habit and is considered Vulnerable.
Nepenthes rajah, also known as the giant montane pitcher plant, is native to Borneo and its traps grow 41 cm (16.1”) tall alone. (1)
One exceptionally large N. rajah pitcher, measuring 41 cm (1 ft 4.1 in) tall, was found on a plant encountered on 26 March 2011 during a Sabah Society visit to Mesilau, on the east ridge of Mount Kinabalu in Sabah province on Borneo.
This plant is considered the largest by volume of liquid held, though others have been observed climbing higher or growing in larger thickets with more slender traps.
Which Carnivorous Plants are Good for Beginners?
Carnivorous plants are notoriously “difficult” for complete beginners because they are different from how someone might treat a leafy, non-carnivorous houseplant. The basic fact that the plant makes a habit of consuming small mammals and insects tends to throw the new caretaker for a loop.
The type of climate the plant thrives in will change the difficulty as well – if you’re trying to raise a tropical plant in a temperate zone, for example, it can be more of a challenge than you thought you were signing up for.
A good way to think about the environment of any plant, not just carnivorous plants, is that it will always thrive in conditions similar to its native environment.
For example, Cape Sundews, named after their native environment along the Cape in South Africa, will thrive in conditions that closely mimic this Mediterranean climate, while Venus Flytraps will thrive best in conditions that mimic their native region of the humid, coastal bogs of North Carolina, US.
Beginner Plants – Tropical Region:
Drosera capensis, the Cape Sundew, is an ideal tropical plant with sticky tendrils that emerge from the base like hairy octopus tentacles. These tentacles capture flies and other insects that happen to buzz by and curl up over the insect once they’ve been caught to begin digesting them.
Another tropical choice is Nepenthes rafflesiana, which is known as Raffles’ pitcher plant. This pitcher plant sports a green, upright trap hung from long stems, with deep red spackling and cilia along the sides of the trap.
Beginner Plants – Temperate Region:
Dionaea muscipula is the most well-known carnivorous plant, also called the Venus flytrap for reasons you might find surprising. This plant has flat, ribbed leaves that end in a two-lobed trap with eyelash-like cilia on each side. This trap snaps closed when an insect lands inside, and the cilia interlock to cage it inside the trap.
Sarracenia Leucophylla is another gorgeous temperate plant, commonly known as the Crimson pitcher plant. These can grow quite tall, and the green trap emerges directly from the base, fading to white with deep red spackling. Sometimes, the red spackling is not present.
Where Can I Buy Carnivorous Plants?
You might have seen some carnivorous plants in retail or department stores, but buyer beware: these plants won’t be in great condition. These department store nurseries often keep these plants in conditions that are not ideal for growth, and they typically get thrown out once they enter dormancy.
Unless you are able to snag these plants the day they come into the store, they are more prone to become weak and sickly based on how they were cared for at the nurseries.
If you can, shop for carnivorous plants at local nurseries, or orchid nurseries. These shops are more likely to have carnivorous plants that are well-maintained and in good health.
With enough due diligence, Etsy is a good choice as well. If you are purchasing carnivorous plants online, make sure to follow the seller’s advice for potting, or, if possible, purchase them already potted.
The Importance of Carnivorous Plant Conservation
Today, there are many threats to carnivorous plants, a quarter of which are considered in a vulnerable, near extinct, or endangered status. There are several factors impacting their likelihood of survival in the coming years:
- Habitat Loss
- Climate Change
- Fertilizer Run-off
- Pesticide Pollution
- Suppression of Natural Habitat Functions
- Wetland Drainage
To make matters worse, a quarter of all carnivorous plant species are considered at high risk of extinction in the coming years due to human disturbance and development and changes in the local climate. (1)
Many of the world’s 860 species of CPs are found in wetland habitats, which represent some of the most cleared and heavily degraded ecosystems on Earth.
It is possible for carnivorous plant keepers at home to help keep these species alive over the coming years by growing healthy, hardier plants that can grow in increasingly varied environmental conditions.
If you are interested in aiding the conservation of carnivorous plants, there are many ways you can help.
- Purchase Land
The most straightforward option is to, when possible, purchase and protect land where at-risk carnivorous plant species are confirmed to inhabit. While this option might not be practical for many people, it is one of the best ways to protect at-risk species and ecosystems.
- Avoid Contact
If you come across wild carnivorous plants, avoid touching these plants as it can close traps and weaken the plant by activating the trap without food inside.
- Keep Ethical, Nursery Grown Plants
By keeping nursery-grown plants, you can help develop hardier, healthier plants while supporting other growers.
- Get Involved
By educating yourself on the current conservation efforts and learning about where these plants grow in the wild, you can help support these efforts through donation or volunteer work as well. The International Carnivorous Plants Society, or ICPS, is heading a large amount of conservation effort for carnivorous plants across the world currently.
- Guinness World Records, Largest Carnivorous Plant Species, https://www.guinnessworldrecords.com/world-records/407396-largest-meat-eating-plant
- Adam T. Cross, Conservation of Carnivorous Plants in the Age of Extinction, https://www.sciencedirect.com/science/article/pii/S2351989420308131