|Plants that kill|
Discover the UK's carnivorous plants, and how they lure their victims to a nasty end.
Words: Peter Marren
Images: Adrian Davies/BBC NHU and Natural Image/Bob Gibbons
Spare a thought for the midges
Anyone who has sploshed over a peat bog on a still, hot day will know what paradises they are for insects, especially the biting sort. But spare a thought for those midges. British bogs are full of plants that have turned the tables on the insect world and will capture, kill and eat every gnat, bug and ant they can catch.
The best known carnivorous plants are the sundews, reddish, jewel-like plants covered with glistening blobs held on long hairs, like threads of glass. Then there are the butterworts, with exotic-looking flowers suspended above sticky leaves. Finally, and mostly under water, are the bladderworts, with what look like tiny flotation bags among the thread-like leaves.
Eleven species in Britain
We have three species of sundew, two butterworts and six bladderworts. Bladderworts are strange, stripped-down plants, without roots or much of a stem and, more often than not, without flowers either. They drift just below the surface in peaty pools and fen dikes, and become conspicuous only when the flowers appear above the water, like bright yellow flags. Unfortunately, most of the diagnostic features are in the flowers, which is why two species were overlooked until the 1980s.
How do bladderworts catch their prey?
Glue and fly-traps are easy to understand. But how do bladder traps work? Under the microscope, each transparent bladder has an inner coating of glands. These are capable of absorbing water, which creates a partial vacuum. Any tiny animal - water fleas, midge larvae and worms - touching the trigger bristles at the neck of the bladder is sucked inside in a millisecond. While the bristles block any escape, the versatile glands secrete enzymes, which slowly digest the edible parts of the luckless creature.
Carnivorous plants make sacrifices for their unusual way of life. Much of their energy is directed towards growing traps, which along with the production of digestive enzymes, reduces their photosynthetic efficiency. This way of life is limiting, and they are restricted to wet, low-nutrient environments in full sunshine. This makes them vulnerable.
Carnivorous plants are in decline throughout lowland Europe. It seems the plants are disappearing at a faster rate than their habitat, which means it cannot be just a question of drainage. The more likely cause is eutrophication. We have swamped the land and water in fertility chemicals. Increased soil fertility and murky, silt-laden water are bad for carnivorous plants, since they increase the competition from other vegetation, which effectively shades them out.
Carnivorous plants prove you don't need a brain and swift movements to be an efficient hunter. They demonstrate the extraordinary versatility of leaves. And they have become the most cunning of hunters, relying not on strength but on the universal lure of beauty and desire.Find out more about Britain's native and introduced plants at www.plantlife.org.uk