Carnivorous plants

 

 

USA-Canada 1992
California pitcher plant, or cobra plant (Darlingtonia californica), is the only species of pitcher plant in western North America, here photographed at Cave Junction, Oregon. (Photo copyright © by Kaj Halberg)

 

 

USA 2012
British naturalist Charles Darwin (1809-1882) called the Venus flytrap (Dionaea muscipula) “one of the most wonderful plants of the world.” – One of the traps on this plant has shut, when two of the three trigger hairs inside the trap were touched within a certain period of time. – Carolina Beach State Park, North Carolina. (Photo copyright © by Kaj Halberg)

 

 

Most flesh-eating plants have one thing in common: They grow in nitrogen-poor soils. To obtain the necessary nutrients, they have evolved various means of catching insects and other small invertebrates. Enzymes, produced by the plants, break down the outer chitin layer of the animals, while bacteria, or other enzymes, make nitrogen and other nutrients in the animals digestible for the plant.

 

Pitcher plants
Pitcher plants belong to five genera, which have one character in common: their leaves are highly modified, forming trumpet-, tube-, or bag-shaped pit-fall traps, called ‘pitchers’, which contain fluid. These plants emit fragrance, luring insects and other tiny animals into the trap. If these animals do not immediately drown in the fluid, they are prevented from escaping by various means.

Nepenthes is the largest of the five genera, comprising about 150 species, most of which are found in Southeast Asia, with a few species in Madagascar, the Seychelles, India, Sri Lanka, Australia, and New Caledonia. Most species are climbers, often several metres long. The midrib of the leaf is prolonged into a tendril, which forms a globe- or tube-shaped pitcher. Usually, two types of pitchers are produced, larger ones near the ground, and smaller ones higher up. The ‘lip’, or peristome, around the upper edge of the pitcher is very slippery, causing tiny animals to slide into the trap. The fluid in the pitcher is viscoelastic, causing winged insects to be unable to escape. Along the inner edge is a row of stiff, down-pointing hairs, which prevent prey from escaping. Above the peristome is an umbrella-like cover, the operculum, the purpose of which is to prevent excess rainfall into the pitcher.

Sarracenia, often called trumpet pitcher plants, comprise 8 to 14 species, depending on the authority. This genus is found in eastern North America, from Newfoundland and Labrador southwards to Florida, and westwards to the Great Lake area. Like Nepenthes, these plants are equipped with a slippery peristome, and an operculum.

The genus Heliamphora, of the family Sarraceniaceae, comprising 23 species, is endemic to South America. They are known popularly as sun pitcher plants, or marsh pitcher plants.

Darlingtonia, likewise of the family Sarraceniaceae, contains but a single species, the California pitcher plant, or cobra plant (D. californica), which is the only pitcher plant in western North America. Fragrance from nectar, emitted by the plant, lures insects into the long, tube-shaped pitchers, which are filled with fluid.

The fifth genus of pitcher plant is Cephalotus, with a single species, C. follicularis, forming a family of its own, Cephalotaceae. It is restricted to a small area in south-western Australia.

 

 

Malaysia 1984-85
Malaysia 1984-85
Borneo is home to many species of Nepenthes. This species, N. villosa, is quite common in Gunung Kinabalu National Park, Sabah. The lower picture shows the peristome, equipped with a row of stiff, down-pointing hairs, which prevent prey from escaping. (Photos copyright © by Kaj Halberg)

 

 

Sri Lanka 2015
Sri Lanka 2015
Two Sri Lanka pitcher plants (Nepenthes distillatoria), encountered in Sinharaja Forest Reserve, south-western Sri Lanka. This species is endemic to Sri Lanka. (Photos copyright © by Kaj Halberg)

 

 

Malaysia 1984-85 
Large species of pitcher plants occasionally catch small vertebrates, such as mice and lizards. This picture shows a large natural hybrid, Nepenthes villosa x N. rajah, known as N. x kinabaluensis, found in Gunung Kinabalu National Park, Sabah, Borneo. (Photo copyright © by Kaj Halberg)

 

 

USA 2012
USA 2012
USA 2012
The pitcher plant genus Sarracenia is found in eastern North America. These pictures show yellow pitcher plant (S. flava), photographed in Carolina Beach State Park, North Carolina (top), and in Green Swamp Preserve, North Carolina. The bottom picture shows an aberrant reddish form. (Photos copyright © by Kaj Halberg)

 

 

USA 2012
USA 2012
Most Sarracenia species have tall, narrow pitchers, but those of purple pitcher plant (S. purpurea) are short and rather broad, sitting close to the ground. Note the numerous down-pointed hairs in the pitcher, which prevent prey from escaping. Incidentally, this species is the official flower of Newfoundland and Labrador. – Green Swamp Preserve, North Carolina. (Photos copyright © by Kaj Halberg)

 

 

Jylland 2017b
Both purple and yellow pitcher plant have been widely introduced in Europe, often illegally planted in marshes, where they tend to become invasive, if they are not controlled in time. This picture shows a mixed growth of the two species in a marsh in central Jutland, Denmark. (Photo copyright © by Kaj Halberg)

 

 

USA 2000-01 
Hooded pitcher plant (S. minor) differs from other Sarracenia species by its operculum, which forms a hood over the pitcher. This species and S. psittacina are the only members of the genus to have translucent patches on the pitcher, which confuse prey species. As they try to escape through these ‘windows’, they are lured further into the pitcher, away from the entrance. – Okefenokee Swamp, Georgia. (Photo copyright © by Kaj Halberg)

 

 

USA-Canada 1992
USA-Canada 1992
California pitcher plant (Darlingtonia californica), Cave Junction, Oregon. The upper picture shows a flowering plant, the lower a brightly coloured pitcher with numerous translucent spots, which lures prey away from the entrance, similar to what is found in Sarracenia minor (previous picture) and S. psittacina. (Photos copyright © by Kaj Halberg)

 

 

Butterworts
Butterworts (Pinguicula) have succulent leaves with glands, which produce droplets, luring tiny insects and other invertebrates to the sticky surface of the leaf. Once an animal begins to struggle, trying to escape, more mucilage is produced, while other glands release enzymes, which break down the chitin layer of the animal, thus releasing nitrogen, which can be absorbed by the plant. The generic name Pinguicula is diminutive of the Latin pinguis = fat (compare the word ‘penguin’), which, like the common name butterwort, refers to the slimy and fatty leaves.

About 80 species of butterwort are presently known, with the largest number found in Central and South America, while 12 species are native to Europe, 9 to North America, and a few to northern Asia.

Formerly, in large parts of northern Europe, it was common practice to apply leaves of butterwort to milk to make it separate or thicken. German farmers would place butterwort plants in water, later using this water to make tough or newly cut meat tender.

In folk medicine, the plant has especially been used to heal wounds and various skin problems. In Denmark, in the 1900s, when many children were suffering from ringworm and other skin ailments, the affected parts were smeared with butter, or leaves of butterwort. In his thesis from 1688, De usu plantarum, Danish herbalist Ole Borch recommends butterwort for treatment of ”hectica febris legitimatrue consumption – and hernia.” You must apply a compress of milk, mixed with moss or butterwort roots on the affected parts, not only for healing, but also to give it back its natural humidity.

Butterwort was also used to treat cracks in cow udders, applying the slime of the leaves to the udder and teats. On an excursion in 1747, an apprentice of Swedish naturalist Carl von Linné (1707-1778), also known as Carolus Linnaeus, says that ”in Switzerland, Pinguicula is used externally on fissuris mammarum, even if the udder becomes hardened, so that it will milk blood.”

In the old days, in Denmark, farmers were convinced that if sheep would consume butterwort “before Michaelmas” (September 29), they would get liver flukes (Distoma hepaticum). The real cause for the sheep to get these parasites was that they were grazing in wet areas, where not only this plant thrives, but also the flukes.

(Source: Brøndegaard, 1961)

 

 

Bornholm 2008b
Island-Færøerne 1999
Common butterwort (Pinguicula vulgaris) with remains of digested insects on their leaves, photographed on the island of Bornholm, Denmark (top), and in Aðaldal Valley, northern Iceland. This species has a circumboreal distribution, found in most of Europe, Russia, Canada, and the United States. (Photos copyright © by Kaj Halberg)

 

 

Alperne 1968-2001 
The Alpine butterwort (Pinguicula alpina) has a wide distribution, found in montane areas of Europe, in the Himalaya, and along Arctic shores, from northern Scandinavia eastwards through Siberia. – Rinnbach, Pongau, Austria. (Photo copyright © by Kaj Halberg)

 

 

Chukotka 2011
The colourful spoon-leaved butterwort (Pinguicula spathulata) is found in eastern Siberia, here photographed on the Chukotka Peninsula. (Photo copyright © by Kaj Halberg)

 

 

Bladderworts
Bladderworts (Utricularia), comprising at least 200 species, has a very wide distribution, found in almost all parts of the world. Members of this genus capture small animals by means of bladder-like traps. The pressure inside the bladder is negative, compared to its surroundings. When trigger hairs on the trapdoor is touched by a tiny animal, the prey, along with the water around it, is sucked into the bladder, whereupon the door closes again, the whole procedure lasting only 1/10,000th of a second. This genus comprises aquatic as well as terrestrial species. Aquatic species catch larger prey like water fleas and nematodes, whereas terrestrial species catch tiny organisms like protozoa and rotifers.

 

 

Sjælland 1969-2005 
The geographic range of southern bladderwort (Utricularia australis) is vast, as it is found in Europe, most of Asia, the southern half of Africa, Australia, and New Zealand. The specific name ‘australis’, as well as the common name ‘southern’, refer to the fact that this species was described from a specimen, found in Australia in 1810. – This picture is from Zealand, Denmark. (Photo copyright © by Kaj Halberg)

 

 

USA 2012a
In North America, the greater bladderwort (Utricularia macrorhiza) replaces the common bladderwort (U. vulgaris) of Europe and Asia, which it closely resembles. In the background leaves of fragrant water-lily (Nymphaea odorata). – Crystal Lake Conservation Area, Haverhill, Massachusetts. (Photo copyright © by Kaj Halberg)

 

 

Jylland 1977-90 
Lesser bladderwort (Utricularia minor) can be identified by its pale-yellow flowers, which are only 5-8 mm long, with a very short spur. – Jutland, Denmark. (Photo copyright © by Kaj Halberg)

 

 

USA 2000-01
Inflated bladderwort (Utricularia inflata), Cape May State Park, New Jersey, United States. The name refers to the inflated leafstalks. (Photo copyright © by Kaj Halberg)

 

 

Nepal 2009-1
Nepal 2009-1
Utricularia brachiata is a tiny terrestrial species of bladderwort, here growing among moss on a rock in Langtang National Park, Nepal. Terrestrial species of this genus catch tiny prey, such as protozoa and rotifers. (Photos copyright © by Kaj Halberg)

 

 

Sundew
Species of sundew (Drosera) obtain the major part of their nutrients by catching small invertebrates by means of glandular hairs on their leaves. When an animal gets stuck in the sticky juice from these glands, the leaf envelops the unfortunate victim, whereupon enzymes dissolve its body juices, making nitrogen and other nutrients available for the plant.

These plants are called sundew, because the sticky glandular hairs resemble dew drops, when the sun shines on them. Formerly, in European folk medicine, dew drops were said to possess miraculous qualities, and the glandular ‘drops’ of sundew were sold as ‘Virgin Mary’s tears’. Supposedly, they were able to cure skin diseases like warts, ringworms, and corns, besides many other ailments.

In the old days, in Denmark, farmers were convinced that if sheep would consume sundew “before Michaelmas” (September 29), they would get liver flukes (Distoma hepaticum). The real cause for the sheep to get these parasites was that they were grazing in wet areas, where not only these plants thrive, but also the flukes. (Brøndegaard, 1961)

About 180-190 species of sundew are known to science. The genus is widely distributed on all continents, with the exception of Antarctica.

 

 

Bornholm 2008a
Bornholm 2008a
In these two pictures from the island of Bornholm, Denmark, flies have been caught in glandular hairs of round-leaved sundew (Drosera rotundifolia). The fluffy, whitish hairs are seeds of willow (Salix). (Photos copyright © by Kaj Halberg)

 

 

Fanø 2001-12
Fanø 2001-12
Oblong-leaved sundew (Drosera intermedia) has a wide distribution, found in Europe, the eastern half of North America, northern South America, and Cuba. These pictures are from the island of Fanø, Denmark. (Photos copyright © by Kaj Halberg)

 

 

Jylland 2006-13
Jylland 2013-15
Insects, which have been trapped in glandular hairs of oblong-leaved sundew. The upper picture shows two common blue damselflies (Enallagma cyathigerum), of which one has already dried out, while the other has just been caught. The lower picture shows a species of butterfly, belonging to the family Lycaenidae. – Jutland, Denmark. (Photos copyright © by Kaj Halberg)

 

 

Nepal 2009-1 
The leaves of this crescent-leaved sundew (Drosera peltata) are heavy with monsoon rain. This species is distributed in montane areas, from the Himalaya across Southeast Asia to Australia. – Langtang National Park, Nepal. (Photo copyright © by Kaj Halberg)

 

 

Venus flytrap
Venus flytrap (Dionaea muscipula) is the only member of the genus Dionaea, which belongs to the sundew family (Droseraceae). It is widely cultivated as a house plant around the world, but has a very limited distribution in the wild, found only in a few localities in North and South Carolina, United States. Populations in New Jersey may be escapes from cultivation.

This plant was described in 1759 by the North Carolina governor Arthur Dobbs (1689-1765), who wrote: “But the great wonder of the vegetable kingdom is a very curious unknown species of sensitive; it is a dwarf plant; the leaves are like a narrow segment of a sphere, consisting of two parts, like the cap of a spring purse, the concave part outwards, each of which falls back with indented edges (like an iron spring fox trap); upon any thing touching the leaves, or falling between them, they instantly close like a spring trap, and confine any insect or any thing that falls between them; it bears a white flower: to this surprising plant I have given the name of Fly Trap Sensitive.” (Dillwyn, 1843)

Venus flytrap – by Swedish naturalist Carl von Linné (1707-1778), also known as Carolus Linnaeus, called a “miraculum naturæ”, and by British naturalist Charles Darwin (1809-1882) called “one of the most wonderful plants of the world” – is unique among flesh-eating plants in having highly modified leaves, which act like a snap-trap, when stimulated in a certain way. On the inner surface of the trap are three stiff hairs, and two of these must be stimulated within a short period of time to trigger the trap. This mechanism has been developed to prevent the plant from using energy on shutting the trap, if e.g. a withered leaf by chance falls into it. Thick, stiff protrusions, or cilia, along the edge of the trap form ’bars’, which prevent prey from escaping.

 

 

USA 2012
USA 2012
USA 2012
Venus flytrap (Dionaea muscipula), Green Swamp Preserve, North Carolina. In the bottom picture, a trap has opened, when the nutrients of a trapped insect have been utilized. (Photos copyright © by Kaj Halberg)

 

 

USA 2012
USA 2012
This new leaf of Venus flytrap is opening up (top). Flowering plant (bottom). – Carolina Beach State Park, North Carolina. (Photos copyright © by Kaj Halberg)

 

 

Portuguese sundew
Portuguese sundew (Drosophyllum lusitanicum) has a restricted distribution, found only in Spain, Portugal, and Morocco. Formerly, it was regarded as belonging to the sundew family (Droseraceae), but has now been placed in a family of its own, Drosophyllaceae.

Portuguese sundew is one of the few carnivorous plants, which is able to thrive on dry, alkaline soils. The leaves, which are 20 to 40 centimetres long, uncoil from a central rosette. The plant emits a sweet aroma, which attracts insects. When they land on a leaf, or on the stem, they get stuck in the numerous sticky glandular hairs.

 

 

Sydspanien 2005
Portuguese sundew (Drosophyllum lusitanicum), Cortes de la Frontera, Andalusia, Spain. (Photo copyright © by Kaj Halberg)

 

 

References
Brøndegaard, V.J. (1961). Vibefedt i folkemedicinen. Farmaceutisk Tidende 71, pp. 957-962. Taken from: Håkan Tunón (ed.). Etnobotanik. Planter i skik og brug, i historien og i folkemedicinen. Vagn J. Brøndegaards biografi, bibliografi og artikler i udvalg på dansk, Vol. 1, pp. 507-513. Published by Centrum för biologisk mångfald, Uppsala, & Kungl. Skogs- och Lantbruksakademien, Stockholm, 2015
Dillwyn, L.W. (1843). Hortus Collinsonianus. An account of the plants cultivated by the late Peter Collinson

 

 

(Uploaded August 2016)

 

(Revised January 2018)