When someone mentions carnivorous plants, what first comes to my mind are venus fly traps and pitcher plants. Pitcher plants generally are found in areas with low soil nutrients, to obtain their required nutrients they feed on insects (they are insectivorous) which they attract through various mechanisms including nectar baits, odours and colouration. Pitcher plants catch insects using a strategy known as pitfall trapping. Generally the underside of the lid (termed the operculum) will have some form of bait that insects will crawl to or land on in an attempt to reach. They are then in a precarious position where they can fall into the mouth of the pitcher below. Within the pitcher is a fluid that contains digestive enzymes that can break down and dissolve the insects. The walls of the pitcher can then absorb the fluid, providing nutrients to the pitcher plant. The walls of the pitcher above the fluid will often have wax scales, lubricant glands or downards pointing hairs to prevent the captured prey from escaping. Most pitchers plants belong to either the old world pitcher plants (Family Nepenthaceae) where the pitchers are derived from modified leaf tips, or the new world pitcher pants (Family Sarraceniaceae) where the pitchers are formed from the whole leaf rolled into a tube and fused along the join. The two groups are not closely related. Lets get an appreciation of this diverse group of plants by taking a took at 10 different pitcher plant species.
Native to two neighbouring mountains in Sabah, Malaysia (Mount Kinabalu and Mount Tambuyukon), this endangered pitcher plant boasts the title of having the largest pitcher in the world. The giant pitchers can grow to a width of 20 cm (8 inches) by a height of 41 cm (16 inches) and can hold around 2.5 litres of digestive fluids inside, enabling it to dissolve its prey. Its diet includes frogs, lizards and even small birds and mammals, although normally only animals that are too sick to scramble out of the pitcher fall victim. Only one other species of pitcher, Nepenthes rafflesiana, has ever been recorded with captured mammal prey in the wild. Its main source of nutrition comes from insects, in particular ants. The fluid inside the pitchers is not entirely hostile however and many organisms have formed a mutual symbiosis (where both species benefit) with the plant, some only able to live within the fluid of pitcher plants (termed nepenthebionts). In this species, two such species of mosquito larvae live within the fluid (Culex rajah and Toxorhynchites rajah). This plant also has a fascinating relationship with the Mountain Treeshrew (Tupaia montana). The underside of the lid of the pitcher produces a sweet nectar that attracts the Treeshrew to feed. Treeshrews apparently like to defecate where they feed as a way of marking their feeding territory. It just so happens that the distance between the underside of the lid to the mouth of the pitcher is the same length as the body of the average Treeshrew, which means the droppings end up right where the plant wants them, inside its pitcher. The Treeshrew is active during the day but there is another critter, the Summit Rat (Rattus baluensis) which behaves in a similar manner but is nocturnal, taking on the task of providing the pitcher with droppings during the night. The common names for this pitcher plant include Giant Pitcher Plant, Rajah Brooke's Pitcher Plant, Giant Malaysian Pitcher Plant and King Of Nepenthes.
Endemic to northwestern Borneo this climbing pitcher plant can reach up to 20 m (66 feet) into the rain-forest canopy, making it the tallest pitcher plant in the world. Its stem, growing up to 3.5 cm (1.5 inches) in diameter is also thicker than any other Nepenthes species. The pitchers grow fairly large, up to 25 cm (10 inches) high, 16 cm (6 inches) wide and hold up to a litre of fluids. They have two rows of fringed wings leading from the base of the pitcher to the opening of the mouth. There are also two forward-facing 3 cm (1 inch) long spurs just under the lid, hanging over the mouth of the pitcher. There are two theories of the purpose of these spurs. The first is that they act as a deterrent to monkeys and other tree dwelling mammals that try to steal the trapped insects, although monkeys have been observed tearing a hole in the side of the pitchers to avoid the spurs. The second is that these spurs act as a precarious place for insects walking across to fall from and end up in the digestive fluids below. This theory is backed up by the fact that the spurs contain one of the largest nectaries (nectar producing glands) of any plant, tempting insects to their fate with the sweet liquid produced. These spurs have also inspired the common name for this plant, the Fanged Pitcher-Plant. This species also forms a mutualistic relationship with a species of nepenthebiont ant (Camponotus schmitzi) which nest in the hollow tendrils of the plant. The ants help pitcher by feeding on some of the captured prey, preventing putrefaction of the pitcher fluid which could in turn lead to the demise of other symbiotic organisms inside the fluid (that are also beneficial to plant) and sometimes the pitcher itself. In addition the plant gains the benefit of having an army of defenders against insect attack. Occasionally the odd ant will also fall into the pitcher fluid while trying to retrieve prey and drown, providing the pitcher with fresh food.
Endemic to New Guinea and its surrounding island, this epiphytic (able to grow without soil), lowland pitcher plant can be found growing in thick moss on tree trunks or sediment bars along rivers. The pitchers can grow quite large, reaching a height of 35 cm (14 inches). This species is quite remarkable in that its prey consists almost entirely of one type of insect, big-winged cockroaches. When the contents of the pitchers were examined these cockroaches were found in abundance. It is theorised that these cockroaches are attracted to an odour produced by this pitcher, but little in the way of research has been undertaken on this species of pitcher plant.
Endemic to Borneo, this pitcher is characterised by having a covering of fine brown hairs most prominent on the stems and leaf under-surfaces, but also present on the pitchers and even the flowers. In fact its species name, hirsuta is derived from the latin hirsute which means covered in hairs. The pitchers are almost entirely green in colour although some will also have red blotches on the inner surfaces. Its hairiness has gained it the rather unfortunate, but fitting common name of the Hairy Pitcher-Plant.
Endemic to Sumatra, this climbing pitcher plant is unique in that its upper pitchers completely lack a peristome (lip) and have a greatly reduced operculum (lid). The upper pitchers are also larger than the lower pitchers (which look similar to other pitcher plant pitchers) reaching a height of 9 cm (3.5 inches) and width of 5 cm (2 inches) and are distinctively funnel-shaped. Rather than having a thin, watery pitcher fluid, this species instead has a thick, sticky, mucilaginous (mucus-like) pitcher fluid. Because of this if the pitcher were to fill with rain (due to the reduced operculum) and tip over, the rainwater would fall out but the pitcher fluid would remain inside and the pitcher. No longer carrying the extra weight of the rainwater, the pitcher would spring back into its normal upright position. Due to its stickyness the pitcher fluid also traps insects flying above the surface of the fluid that happen to make contact with it. It is thought that the lid also has glands which produce a substance that intoxicates insects walking on it, causing them to fall into the sticky fluid below.
Native to Borneo, Peninsular Malaysia and Sumatra, this pitcher plant has quite small pitchers reaching a height of 15 cm (6 inches) and width of 4 cm (1.5 inches). However they are quite remarkable in that they have a band of white trichomes (fine outgrowths) underneath the peristome (lip) of the pitcher. These are here to attract termites which like to feed on them, a large colony of termites can strip a pitcher bare of trichomes within an hour. Termites though are not particularly clever and many end up falling into the pitcher fluid and drowning, providing food for the pitcher plant. This was first observed when after a single night the pitcher that on the previous day had a full band of trichomes, had none and its fluid had filled with termites. The band of white trichomes gives this pitcher plant its common name the White-Collared Pitcher-Plant.
Moving away from the Nepenthaceae family pitchers we will now look at some of the unrelated pitchers in the family Sarraceniaceae. The first of which goes by the common name of the Parrot Pitcher Plant. Native to the southeastern United States, this pitcher plant is unique in that it has almost horizontal pitchers. The pitchers produce nectar around the rim of their mouth to attract their insect prey. Insects feeding on the nectar will mistakenly enter the mouth in search of more delicious nectar. Once inside the insect becomes confused by the light shining through multiple semi-transparent patches along the tube, thinking these are exits the insect will crawl deeper into the pitcher where the light is brighter and away from the actual mouth of the pitcher. Criss-crossing, downwards-facing hairs inside the tube also prevent the insect from escaping once inside. This species is often found partially submerged in the wild, and has been recorded to catch aquatic invertebrates and even tadpoles when the pitchers are underwater.
Endemic to Chimanta Tepui in Venezuela this pitcher plant belongs to the Heliamphora genus, collectively known as Marsh Pitcher Plants or Sun Pitchers. Most species in this genus do not produce their own digestive enzymes (except one species, Heliamphora tatei which does), instead relying on symbiotic bacteria to break down captured prey. They do however attract prey using colour, chemical signals and nectar and rely on the same pitfall strategy as all other pitcher plants. Because they have no lid, to avoid rainwater filling up the tube and overflowing (taking with it any captured prey), these pitchers have a small slit in the side of the tube which allows excess water to drain but is small enough not to allow prey items to fall out. At the tip of each tube is a small curved spoon that produces nectar at its tip, which attracts insects and places them in a precarious position over the mouth of the tube.
Endemic to cold water bogs in the states of Northern California and Oregon in the United States of America, this pitcher plant like Sarracenia psittacina uses semi-translucent false exits to confuse insects once they enter the mouth of the pitcher. It also has similar downwards pointing hairs to guide the insect towards certain death at the bottom of the tube. Despite being able to regenerate from the roots after fire, the roots of this species are quite sensitive. This plant inhabits areas that can exceed 25 degree Celcius, however their roots will begin to die back in temperatures exceeding 10 degree Celcius. The benefits behind this particular adaptation are not well understood. The plants common name, Cobra Lily, comes from the shape of the bent-over pitcher tube and the two sections of the leaf that branch off from the tip of the tube, resembling the forked tongue of a cobra.
Endemic to the southwest coast of the state of Western Australia in Australia, this little pitcher plant is remarkable in that, despite looking like it should fit in the Nepenthes genus, it is in fact more closely related to strawberries and roses than it is to any other pitcher plant. It is the sole species in the genus Cephalotus. This pitcher plant produces both evergreen simple leaves which lie close to the ground and insectivorous leaves (the pitchers). The pitchers are quite hairy, especially along the ridges. The operculum (lid) also has transparent patches that confuse insects into thinking they are patches of sky. There is a species of ant-like wingless fly, Badisis ambulans, that rely on this pitcher plant. The larvae of this fly have only ever been found inside these pitchers. Its common names include Albany Pitcher Plant, Western Australian Pitcher Plant, Fly-Catcher Plant and Mocassin Plant.
Brooke Lorren from Mesa, Arizona on November 20, 2011:
Excellent work. There's a lot of interesting information about pitcher plants here. Love the pictures.
danielleantosz from Florida on November 20, 2011:
Wow, great information! I love the pitcher plants and had no idea there were so many kinds. Thanks.
Linda Crampton from British Columbia, Canada on November 19, 2011:
This is a fantastic hub! The information and photos are fascinating and well presented. Thank you so much for sharing this information about pitcher plants. I enjoyed your hub very much.