Carnivorous plants are the name given to a wide ranging group of plants which only share a single common factor, that is that they all have a method of trapping and digesting living creatures in order to provide a means of nourishment.
How these plants do this varies widely from species to species. Most people think that all Carnivorous plants have traps which shut suddenly on unwary insects. However, the case is that most Carnivorous plants have 'passive' methods of catching their prey, most never move and simply wait for their prey to make a mistake.
Stories of Carnivorous plants being man-eating fiends have also been greatly exaggerated. The majority of Carnivorous plants never grow above a few feet. Even the giant tropical Nepenthes restrict their intake to insects, albeit slightly larger insects.
The cultivation of these plants has often worried newcomers, fearing that the upkeep of these amazing plants is difficult and that the plant rarely outlives a year. This is not the case, if you follow a few simple rules, you should be rewarded with interesting plants which make an interesting point of conversation for many years to come.
Plants can be grown in and out of doors, depending on the type of course, and there are many native British Carnivorous plants. Although most of the plants for sale in the UK come from the USA, there are also species of Carnivorous plants found in Canada, Russia, South America, Asia and Europe.
Types of trap
Traps can be divided initially into active and passive types. Active traps use movement in the process of trapping and digesting their prey, Dionaea (Venus fly trap) being the best known example. The mechanism is reminiscent of an old-fashioned game trap, with two sections hinged open and sprung, waiting to be triggered by the unsuspecting victim. Pinguicula use no movement but catches food with their fly-paper type leaves, but because they roll their leaf margins immediately after trapping to assist digestion they are also classified as active. Similarly, Drosera bend dew-dropped tentacles covering the leaf surface towards the prey, which is stuck to the adhesive droplets, and sometimes bend the entire leaf to surround their food. While they are not as fast as most other active traps, a very few species can bend their leaves in half in less than 60 seconds.
Passive traps such as Sarracenia utilize no movement either in trapping or during digestion. They simply expect the prey to move towards the plant and become ensnared, by falling into a pit or being stuck with a gluey substance.
Traps can also be distinguished by their form. The largest group, known as pitfalls, include all the pitchers. These consist of a tube into which a creature will eventually tumble and are often enhanced with nectaries or colouring to attract the prey, as well as hairs or waxy cells to assist trapping. Sarracenia is a good example of a pitcher which may employ the full range of available inducements. Fly-paper traps, like those of Drosera, use sticky mucus to glue the prey to the leaf blade. The steel-trap of Dionaea snaps shut on any creature unfortunate enough to trigger the sensitive hairs on the trap surface. Mousetraps, such as those of Utricularia, work in a very similar fashion, but suck in the prey in response to being triggered, operating in very wet conditions or under water.
Why do Carnivorous plants trap food?
Carnivorous plants are found throughout the world and in many different habitats - from the acid peat bogs of Britain, where Drosera and Pinguicula grow, to the tropical jungles of southeast Asia, inhabited by the Nepenthes, and the flooded savannahs of Africa, which provide a home for Utricularia.
Many carnivorous plants require permanently wet conditions, as this might suggest, although others live in very dry sandy soils. However, the characteristic common to all their habitats is the lack of nutrients in the soil. By lessening their dependence on the soil for nourishment and by supplementing their diet with food that literally walks or flies in, the carnivores are able to survive where few other plants can. This visiting animal life is an important source of nitrogen - the nutrient which is most easily lost from the soil and which is always rare in soils colonized by carnivorous plants - and nitrogen helps to increase leaf growth and to improve or make possible both flowering and seed production.
Sundew (Drosera)
Introduction
Sundews are found throughout the world and offer a wide variety of size and shape. Many also have attractive flowers. The sundews belong to the 'fly-paper' group of carnivorous plants. This group have sticky leaves which catch and digest insects which are unlucky enough to land on them. The sundews are found in many damp places, peat bogs, swamps or in grassland.
How it works
The leaves of sundews can be long and thin or rounded. Most follow the semi-active rules in that the leaves can move somewhat to fully capture the insect. Movement is usually restricted to the curling up of the leaf to increase the surface area of the leaf against the prey. An insect landing on a leaf will become stuck on the glands which stick outwards from the leaves. Once caught, the insect will be digested by the digestion glands, situated mainly along the centre of the leaf, over a period of a day or so. Mainly the prey consists of small flying insects.
The Lifecycle of the Sundew
As with most other carnivorous plants, the sundew needs a time of winter rest, where the soil is allowed to dampen slightly. For the rest of the year, the plant needs to be kept standing in soft water. Leaf production is slow over the winter period and leaf length is reasonable short. However, as the temperature starts to rise and spring arrives, the leaves start to grow faster and longer, perhaps reaching 4 inches for Drosera capensis. The flowers are produced on long stems, like most carnivorous plants, and the small but colourfull flower heads open for a short time before drying out and dying. Not before the next flower head has opened, however. The outer leaves gradually dry out and can be removed by cutting them off.
How and where to grow them
Grow the plant in the normal type of carnivorous plant soil, peat / sphagnum moss / sand.
Keep the plant standing in soft water (rain water normally) throughout the year, only letting the soil dry out slightly during the winter.
Remove any leaves which turn brown and dry up.
Feeding can be achieved by dropping any small insect, alive or dead, straight onto the leaves.
Stand the plant in full sun, if possible, to promote active growth.
For Drosera capensis which is one of the more common type, the temperature should be kept above 2 oC
Reproduction can be achieved by simply picking out the small off shoots from the main plant which appear from time to time
Venus Fly Trap (Dionaea)
Introduction
By far the most famous of the Carnivorous Plant genre and probably responsible for more people getting involved in this type of plant as anything else. It was certainly the reason that I started growing carnivorous plants! It is the only plant of it's type and is normally found in the Carolina areas of eastern North America. The bogland areas where it normally grows are devoid of the nutrients that it requires, so the plant grows stems which have traps on the end. It is in these traps that the insects are caught.
How it works
A normal plant will grow the stems up to 5 inches (about 13 cm). The trap will consist of two pads which are hinged together on one side only. Along the other edges of the trap are 1/4 inch long spines which stand outward, similar to eyelashes. The trap mechanism is triggered by three hairs which are inside the pads. If you look very carefully at a pad (it's best to look along the hinge), you will see three tiny hairs sticking out from the middle of the pad. Each and every pad has these hair triggers. When an insect crawls into the trap, it must touch either two different hairs, or one hair at least twice. Once this happends, the pads close together very fast. As a precaution against false triggering by inanemate objects or rain etc. the trap will reopen if these hairs are not triggered again. If the captured insect continues to struggle, however, the hairs are continually touched and this forces the trap to close even tighter, until a complete seal is made along the unhinged edge. You can see that the spines have now done their job of keeping the insect from escaping, and have turned outward. It is at this stage that the digestive enzymes are released onto the insect which is slowly eaten away, the nutrients being re-absorbed through the pads themselves. About 4-5 days later, the trap will re-open, revealing the dried up remains of the insect which would normally be blown away by the wind. The new influx of nutrients will lead to new stems being produced from the centre of the plant.
The lifecycle of the Venus Fly Trap
During the spring time, the plants can produce a very long thick stem from the centre of the rosette. This stem can grow over 10 inches high and may be topped with small white flowers which flower for a few days before dying off. The stem itself continues on for a lot longer, however, it can be cut off at the base once it has stopped flowering. The closed heads, if pollenated, may have produced seeds. The summertime produces the main growth and this continues right through to the autumn when the trap production slows. In the winter, the plant enters a dormancy stage. Trap production stops or is produced only very slowly. Don't feed the plant during this time. I'm not sure as to the lifespan of a Venus Fly Trap, however, I have one which is four years old now.
How and where to grow them
The Venus Fly trap likes as much light as it can get. A south facing windowsill is ideal. The traps grow with red middles if they are getting sufficient light, although completely green traps work just as well!
Grow the plant in live or shredded sphagnum moss or in specially prepared compost that is available in some shops. Never use ordinary compost as this is most likely to contain extra nutrients in the soil which could be enough to kill off your plant!
NEVER give it fertilizer of ANY kind. This will do the plant untold damage since it should get it's nutrients from the insects it catches, not the soil.
Stand the pot in a trough of water, rain water is best, but anything that isn't hard. You should aim to keep about 1/4 to 1/2 inch in the trough at all times, so the soil stays nicely damp.
However, during the winter, reduce the watering to a minimum, only once every couple of weeks, just so the soil doesn't dry out completely.
Also, there is no need to water the top of the plant at all, just let the plant soak up the water from the tray.
Resist the temptation to trigger the traps, each closing of the traps will lose the plant some more energy. Obviously, if the plant isn't catching food with these closures, it will slowly get weaker.
Snip off the rotten, brown leaves as they die away.
If you do feed it DON'T use dead stuff, chicken, steak,flies etc!! This is because the traps need their hairs to be continually triggered for a time to allow the digestive enzymes to be released. Now, obviously, your bit of dead chicked won't keep triggering the hairs on the petals once the trap has closed. The trap will then reopen in a few days, without disolving the food.
If your plant hasn't caught anything reciently and you're getting worried, see if you can catch an alive or semi-alive insect that's still moving about. Drop it into a trap and is should perform the required movement to get itself eaten! (I've discovered that fly spray causes the flys in my house to get stunned and fall to the ground. They keep moving, however, for quite a long while, enough time to drop one into a hungry trap!!! I'm not sure if the fly spray affects the plant though, so I never spray near the actual plant. Flys covered in fly spray do not seem to affect my plants, though.)
If you do get a flower stem grow and the plant is still small (under 4 inches diameter) I would cut is off early, because it will be unlikely that it will flower, and the plant looses too much energy producing the stem.
These plants can be grown outdoors, especially if you live in warmer climates than here in the UK. However, I have a VFT in the garden at the moment, buried in it's original pot (to maintain the nutrient free compost) and close to a run used by the local ants. When I first planted it, within half an hour, all six of it's current traps had been triggered!
The temperature must not be allowed to drop below freezing, so I'll have to re-dig up the pot and bring the back indoors before the first frosts arrive in October.
I know it's unlikely, especially if you keep your VFT indoors, but if your VFT catches greenfly or some other horrible small pest that is too tiny to trigger the traps, you can get rid of them by either buying another type of carniverous plant, something like a Sundew, which has sticky petals and will mop up the greenfly if it's planted close to the VFT. Or you can submerge your VFT completely underwater (soft water, mind) for 3 or 4 days. This won't affect the plant in the slightest, and will hopefully drown the greenfly!
Any seeds produced can be planted onto shredded sphagnum moss or pure perlite. It helps to keep the temperature relativly warm - 70 to 80 �F (21-26 �C)
Pitcher Plant (Sarracenia)
Introduction
Only a small handfull of species exist of this type of CP. However, there are a large amount of hybrids and sub-species. They very from the very small (less than 3 inches high) to the magestic (3 feet high). Most are basically green, however some types are yellow, purple or even partly white (Sarracenia Leucophylla). The Sarracenia Flava is named after the Latin for yellow.
How it works
The trap itself is a passive trap which employs no moving parts to catch it's prey. At the top of the pitcher plant is a lid which is fixed and cannot move. The insect lands on this lid and is drawn into the throat of the plant often by the use of nectar or coloured veins which run along the inside of the lid, down into the throat. Onch inside the throat, the insect is trapped by longer and longer downward pointing hairs which stop the insect from returning the way it came. Further down still, the insect reaches a slippery area which contains even more nectar glands.
Finally, the insect reaches the digestive are of the stem, where enzymes are produced. The insect is then digested.
The Lifecycle of the Pitcher Plant
This plant too has a dormant period during the winter. Some of the more hardy species such as S. Flava produce a series of 'mutated' stems which don't grow to full height. These stems are designed to protect the plant against frost. Note that excessive periods of temperatures above about 60 �C can interrupt it's dormant cycle and can lead to poor results the following year.
Come the spring, the plant will produce flowers, as with most other carnivorous plants, these flowers are on tall stems at or above the height of the pitchers themselves. Colours can be yellow, cream, orange, pink or red depending on the species. There are some flowers which give off an attractive smell, whilst others are more unusual. Reproduction of the plant can be achieved through seed or the splitting of the rhizome at the base of the plant.
How and where to grow them
Most of the Sarracenia types are grown in peat / sphagnum moss mixture and perhaps some sand mixed in.
Only repot the plant in spring, repotting out of season can do the plant damage.
Stand the pot in soft water, keeping the compost moist all the time. Reduce the water slightly during the winter.
Reproduction can be achieved by the carefull splitting of the rhizome at the base of the plant. Also making cuts in the rhizome can encourage further shoots to emerge from the cuts.
Sarracenia flava can withstand some frosts, although the leaves may fall away. However, most of the more tender Sarracenias cannot withstand cold temperatures.
The brighter the light that Sarracenia is exposed to, the more vivid the colours will be.
What I am growing
I have two species of Sarracenia,
S. flava, a tall pitcher plant - about 14 inches tall!. This has done very well this year, it's about 4 years old and has flowered two years running now. The flower is bright yellow but has a slight wiff of rotting meat! Although the plant was named as S. flava I must admit to never having seen the yellow tints on the end of the traps. Mine are green right through!
S. hybride, is a new one for me this year, it's a half size pitcher, where the lid of the trap doesn't quite cover over the entrance to the trap. It has the mose delightfull red throats though and is growing freely. It's about 7 inches tall now.
