Invasive species

 

 

 

 

 

 

 

 

 

 

 

The term invasive is sometimes applied to native species, whose numbers increase to an extent that they become harmful to their environment. Three such examples are white-tailed deer (Odocoileus virginianus) in North America, and common broom (Cytisus scoparius) and bracken (Pteridium aquilinum) in Europe.

On this page, the species are divided into three categories: animals, plants, and fungi. Animals are divided into sections on mammals, birds, and invertebrates. Each section is arranged alphabetically according to the scientific family name, generic name, and specific name.

 

 

 

 

 

The taming and usage of the domestic goat is described on the page Animals: Animals as servants of Man.

 

 

 

 

 

 

 

An intense encounter with this animal is related on the page Travel episodes – India 2008: Mountain goats and frozen flowers.

 

 

 

 

 

 

In many parts of North America, it has also spread beyond control. As far back as in 1949, in A Sand County Almanac, environmentalist Aldo Leopold (1887-1948) wrote: “I now suspect that just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer.”

In August 2012, The Bloomberg View published a staff editorial, entitled: “Deer Infestation Calls for Radical Free-Market Solution.”

About two months later, The Wall Street Journal ran a story, entitled: “America Gone Wild,” noting the impact of overabundant deer.

The Nature Conservancy then noted: “No native vertebrate species in the eastern United States has a more direct effect on habitat integrity than the white-tailed deer. (…) In many areas of the country, deer have changed the composition and structure of forests by preferentially feeding on select plant species.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The origin of the domestic cat is described on the page Animals: Animals as servants of Man.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In Australia, 24 European rabbits were introduced in Victoria in 1859. The vast farmlands were an ideal habitat for the rabbits, and the mild winters allowed them to breed year-round, so they quickly spread over most of the country. Australia’s equivalent to the rabbit, the greater bilby (Macrotis lagotis), could not compete with the fast-breeding rabbits, and today it is an endangered species.

Other places of introduction include New Zealand, certain Hawaiian islands, and islands off the coast of South Africa. There are also many instances of pet rabbits, which have escaped, forming feral populations.

In countless cases, this species has done severe damage to the environment, partly through overgrazing, partly through its system of underground tunnels, and partly through competition with local wildlife. It is regarded as an invasive species in most countries.

In 1972, English author Richard Adams (1920-2016) wrote a novel, Watership Down, describing the life of a group of wild rabbits in southern England. Although the rabbits have been anthropomorphized, the story gives a fair account of the life of these animals.

 

 

 

 

 

 

 

 

It is a serious pest, as it competes with native mammalian species, raids birds’ nests, and consumes huge amounts of cereals and other food items. Furthermore, it spreads various diseases among humans. During the Middle Ages, fleas of the brown rat were carrying bubonic plague, which in some places reduced the human population by 50 to 75%. This much feared disease was aptly named The Black Death

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Not only do possums destroy forests, they also do damage on pasture lands, causing a fall in farm production at an estimated 35 million NZ$ annually, and they also eat planted seedlings of pines and other trees. Besides, they can infect cattle with bovine tuberculosis, threatening the country’s valuable dairy industry.

Possums are found virtually everywhere on mainland New Zealand and Stewart Island, although they have been eradicated from major offshore islands since the early 1990s. Their number is difficult to accurately assess, but in the early 2000s, estimates ranged from 50 to 70 million. Their cost to the economy is considerable. In 2006, government agencies spent $111 million on possum control. (Source: teara.govt.nz/en/possums)

 

 

 

 

 

 

The word raccoon was adopted by settlers in Virginia, a corruption of a Powhatan term, meaning ‘the animal that scratches with its hands’. It was variously written as aroughcun or arathkone.

 

 

 

 

 

 

These animals are active throughout the year, and in autumn they store nuts and fruits in underground caches. They are not able to remember where the food was buried, but find it by smelling it under the snow. Grey squirrels are often a nuisance on bird feeders, where they consume most of the food that was intended for birds. In parks and other places, where people regularly feed grey squirrels, they become very tame indeed.

The eastern grey squirrel has been successfully introduced to South Africa, Britain, and other places. In Britain, it is regarded as a pest, as it outcompetes the native Eurasian red squirrel (S. vulgaris), which is now scarce south of Scotland. Extermination campaigns of grey squirrels have been initiated in the U.K., causing the red squirrel to increase in several places.

The specific name refers to the Carolinas. Presumably, the type specimen was collected there.

 

 

 

 

 

 

 

The generic name is derived from the Greek alopex (‘fox’) and chen (‘goose’), alluding to the ruddy colour around the eye, and on the hindneck, back, and inner flight feathers. The specific name means ‘of Egypt’.

 

 

 

 

 

 

 

 

 

 

 

 

 

As early as the 1880s, the sparrow itself was regarded as a pest in New Zealand, and today it is considered a serious crop raider in large parts of North America. It also competes seriously with local species at bird feeders etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In many parts of eastern Taiwan, large numbers of this species have been mass-released during Buddhist festivals. They have become naturalized in many areas, where they compete with – and also hybridize with – the local, endemic Taiwan bulbul (P. taivanus), causing it to have declined drastically, and already gone extinct in Yilan County.

 

 

 

 

 

 

Today, it is very common in Singapore and Taiwan, where it out-competes local bird species, in Taiwan especially the native crested myna (A. cristatellus), which is declining.

A number of pictures, depicting Javan and crested mynas, may be seen on the page Animals – Birds: Birds in Taiwan.

 

 

 

 

 

 

 

“The introduction of European starlings (Sturnus vulgaris) in New York City in 1890 and 1891 resulted in their permanent establishment in North America. The successful occupation of North America (and most other continents as well) has earned the starling a nomination in the Top 100 list of ‘Worlds Worst’ invaders. Pimentel et al. (2000) estimated that starling damage to agriculture crops in the United States was $800 million yearly, based on $5/ha damage. Starlings may spread infectious diseases that sicken humans and livestock, costing nearly $800 million in health treatment costs. Lastly, starlings perhaps have contributed to the decline of native cavity-nesting birds by usurping their nesting sites.”

The starling was first introduced to Cincinnati, Quebec, and New York in the 1870s, and again in New York and Portland, Oregon, around 1890. It quickly spread across the continent, and a recent estimate puts is present number at about 150 million, living from southern Canada southwards to Central America.

As opposed to the situation in the United States, the starling is declining in large parts of Europe, mainly because of persecution in its wintering areas. In later years, the species has begun to spend the night in cities, where it is considered a nuisance because of its droppings. It also does some damage on fruit trees and other crops.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Being highly adaptive, they thrived and soon spread beyond control. Rice shoot are a favourite food of these snails, and, having no natural predators in Taiwan, they have become a huge menace in rice fields. Bright pink masses of snails’ eggs are often seen on concrete surfaces along river and ditches, and also on the rice plants themselves. (Source: culture.teldap.tw)

The golden apple snail is considered to be among the world’s one hundred worst invasive species. (Source: Lowe et al., 2000. 100 of the World’s Worst Invasive Species: A Selection from the Global Invasive Species Database. The Invasive Species Specialist Group, IUCN)

 

 

 

 

 

 

The generic name is derived from Ancient Greek areiones, a kind of snail or slug.

 

 

 

 

 

 

In traditional Chinese medicine, cockroaches are used against a number of ailments, such as abdominal problems, stroke, and bone fractions, and also as an anti-ageing agent. An ethnic minority in the Yunnan Province used cockroaches to treat open wounds. New research has shown that these animals contain at least nine different antibacterial substances, and one substance is able to kill AIDS virus.

For hundreds of years, cockroaches have been utilized as food in northern China. A cream, containing intestines of cockroaches and other ingredients, is applied by Chinese women to their skin to keep it young. A booming industry in the country is producing skin cream and medicine from millions of cockroaches, kept in captivity.

 

 

 

 

 

 

It is relished as a food item in some areas, but elsewhere it is regarded as a pest in agricultural areas and gardens, especially in South Africa and California. Both places it was originally introduced as a food animal, but has become an agricultural pest, especially in citrus groves and vineyards.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It has been introduced to a number of other countries, including England, Ireland, Turkey, New Zealand, and Australia, and is regarded as an invasive in several countries.

 

 

 

 

 

As early as 1741, the famous Swedish botanist Carl Linnaeus (1707-1778) noticed this phenomenon on his journey to the Swedish islands Öland and Gotland. He relates the following: ”The farmers told me that where this plant is growing, it dispels other species. We had clear evidence of this fact, because where ramsons was growing there were no other plants.” (Source: C. Linnæus 1745. Carl Linnæi Öländska och Gotländska Resa, förrättad År 1741 (‘Travels by Carl Linnæus in Öland and Gotland 1741’), new ed. Wahlström & Widstrand 1975)

A popular name of ramsons is bear’s garlic. According to the booklet Chrut und Uchrut (in English called Herbs and Weeds – a useful booklet on medicinal herbs), written in 1911 by Swiss priest and herbalist Johann Künzle (1857-1945), this name was applied hundreds of years ago by people, who noticed that bears, still weak and emaciated after a long winter hibernation, would gorge themselves on leaves of ramsons and thus regain their strength. This fact is reflected in the specific name, from the Latin ursus (‘bear’), applied in 1758 by Linnaeus.

In his book Carl Linnæi Skånska Resa, förrättad År 1749 (‘Travels by Carl Linnæus in Skåne 1749’, new ed. Wahlström & Widstrand 1975), Linnaeus mentions that a local name of ramsons is Sancta Brittæ lök (‘Saint Britta’s onion’), named after Birgitta Birgersdotter (‘Holy Birgitta’), a Swedish saint, born around 1303, who died in Rome 1373 during a pilgrimage to the Holy Land. The following year, her earthly remains were brought back to Sweden and buried in Vadstena Abbey, near Linköping.

 

 

 

 

 

 

 

 

 

 

 

 

 

Lesser periwinkle was first introduced to North America in the 1700s. It has since escaped cultivation in many places throughout the eastern and north-western United States, often invading natural areas and displacing native species. It is also often an invasive in northern Europe and elsewhere.

The word periwinkle, which was first used in English in 1922, was taken from the flower colour of this plant. It is a shade of lavender blue.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The medical usage of these plants is described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

 

 

A South African website, farmersweekly.co.za/animals/horses/beware-those-blackjacks, says: “The common blackjack is not only an irritant to horses, (but) can cause them injury. (…) There can be few of us who have not spent ages picking them off our clothes after walking through the veld to catch horses in the early winter. Blackjacks that become entangled in the forelock of a horse can be a great irritant, and the animal will toss its head, if you try to remove them. The spines can injure the eyes, so it’s better to clip the forelocks short. Blackjacks can also get caught up in the long hair behind the fetlocks and pasterns, causing chronic irritation and lameness.”

This species is reported to be a weed of 31 crops in more than 40 countries, Latin America and eastern Africa having the worst infestations. (Source: cabi.org/isc/datasheet/9148)

However, downy bur-marigold is not only a troublesome weed, it also has medicinal properties. In traditional Chinese medicine, it has been used for a large number of ailments, including influenza, colds, fever, sore throat, appendicitis, hepatitis, malaria, and haemorrhoids. Due to its high content of fiber, it is beneficial to the cardiovascular system, and it has been used with success in treatment of diabetes.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

However, the success of this plant is not only due to its production of seeds. Its many spines cause many animals to avoid eating it, but the smartest ‘trick’ is its root system. The underground stem, which is situated at a depth of 20 to 40 cm, grows lively in all directions, and just a tiny bit of underground stem is able to produce a large colony of plants, sending up stems at regular intervals. Some shoots grow downwards to a depth of a couple of metres, where the ground is always humid. In this way, the plant always has a secure source of water, no matter how dry the weather may be. Also, an even deep-ploughing plough does not reach the deepest stems.

If you want to control creeping thistle in your garden, the best way is to exhaust it by constantly removing the green shoots, as soon as they appear, and keep doing it. As Danish poet Thomas Kingo (1634-1703) expressed it: “Evil weed does not perish by itself.” And a proverb by Danish author Peder Syv (1631-1707) says: “Evil weeds grow fastest and perish latest.” (Source: H. Knudsen 2014. Fortællingen om Flora Danica. Lindhardt & Ringhof, in Danish)

In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes: “(…) it is, perhaps, the worst weed of the entire United States. (…) Its seeds serve as food for goldfinches and sparrows, but even this good turn is offset by the fact that the birds, in getting their food, set free the winged seeds, and wherever those seeds fall trouble begins. The plant is outlawed in every northern State; thirty-seven States in all legislate against this rogue, but outlawing it has had very little effect upon it.”

 

 

 

 

 

 

 

 

 

This plant contains an oil with a turpentine-like smell, which, supposedly, should deter fleas, hence its common name. Another popular name is bloodstanch, given by herbalists, who claim that an extract from leaves and flowers arrests haemorrhages from the lungs and alimentary tract.

Horsetail fleabane also grows in cities, described on the page Plants: Urban plant life.

 

 

 

 

 

 

 

 

 

Leaves, stem and flowers are edible, and the subtle flavour, reminiscent of artichoke, develops after being cooked. It is also dried and ground into powder for usage in soups. In Nepal, juice of the plant is applied to wounds.

Shaggy soldier is probably native to Mexico, but has become naturalized countless places around the globe. It is very often a troublesome weed in vegetable gardens, but in Mexico and China it is used as a pot herb or in salads.

The genus was named in honour of Ignacio Mariano Martinez de Galinsoga (1756-1797), director of the Royal Botanical Garden in Madrid, and physician to the Spanish Queen consort Maria Luisa de Parma. In Britain, the generic name was corrupted to gallant soldiers.

 

 

 

 

 

 

 

The generic name is derived from the Latin solido, meaning ‘to join’, or ‘make complete’. Formerly, several species of goldenrod were reputed to be able to heal wounds.

 

 

 

 

 

It is a large sunflower-like plant with a woody, erect stem, growing to 3 m tall. The leaves are ovate in outline, toothed and pointed, usually to about 20 cm long, occasionally to 40 cm. As its Latin name implies, their shape is diverse, mostly with 3-7 lobes, but sometimes simple. The large, fragrant flowers are bright yellow with an orange centre, to 15 cm across.

Due to its tolerance to heat and drought, Mexican sunflower often invades fallow lands, forming dense stands that outcompete native vegetation. It is regarded as invasive in at least 50 countries.

 

 

 

 

 

 

 

 

It is widely cultivated and has become naturalized in many European countries, North America, New Zealand, and elsewhere. It is considered a noxious weed in many countries, often forming large stands, which expel native species.

 

 

 

 

 

When cooked, the leaves are edible, and the seeds can be consumed raw or cooked. Medicinally, it has been used for treatment of warts, ringworm, and nettle stings, and also to relieve an itchy scalp.

 

 

 

 

 

 

 

 

Garlic mustard has invaded numerous forests, where it is able to dominate the understorey, hereby expelling native plants. It is listed as a noxious species in at least 9 American states.

 

 

 

 

 

At an early stage, it was introduced to many other parts of the world and has become naturalized in numerous countries. It is classified as invasive in California, Hawaii, and some of the Great Lakes states in the U.S., in New Zealand, and on off-shore islands in Chile.

 

 

 

 

 

 

Due to its vigorous growth and production of numerous seeds, it is extremely difficult to control. In many U.S. states, it is classified as a noxious weed, and it is banned in New Hampshire. In New Zealand, the National Pest Plant Accord has declared Japanese honeysuckle “an unwanted organism”.

 

 

 

 

 

 

 

 

It closely resembles the native American bittersweet (C. scandens), with which it readily hybridizes, thus threatening the gene pool of this local species.

 

 

 

 

 

 

 

 

Today, it is regarded as an invasive in many places, including South Africa, Brazil, Galapagos Islands, St. Lucia, Hawaii, and Taiwan. In South Africa, all trade in seeds and cuttings of the species is prohibited.

 

 

 

 

 

 

In America, popular names of this species include Creeping Jenny, alluding to its invasive nature. In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes: “Creeping Jenny is one of the meanest of weeds. That name aptly describes it. A whispering little hussy that creeps in and spoils everything. The weed needs no other name than this, but it has several others (…) hedge bells, corn-lily, withwind, bellbine, lap-love, sheep-bine, corn-bind, bear-bind, and green vine.”

 

 

 

 

 

 

 

It is capable of very rapid growth, sometimes completely entwining trees and bushes, but is also able to creep along the ground. It is regarded as an invasive in many areas, including eastern Australia, southern China, and Taiwan.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

However, it soon became an invasive species, displacing native sun-loving plants by creating dense shade. One bush can produce up to 200,000 seeds a year, and its nitrogen-fixing root nodules allows it to grow in even the poorest soils. Attempts to remove bushes by cutting and/or burning are in vain, as it easily sprouts from the roots. Birds devour the seeds, thus aiding in the dispersal of the species.

Under the Alberta Weed Control Act of 2010, Japanese silverberry is characterized as a “prohibited noxious weed”.

 

 

 

 

 

These plants, comprising about 18 species, have a hollow, jointed, silica-containing stem with 3-40 longitudinal grooves. The leaves, often reduced to scales, are arranged in whorls at each joint. There are two distinct types, of which one has brown, fertile spring shoots and green, sterile summer shoots, which supply the photosynthesis. The other group has only green summer shoots, with terminal sporangies. They vary from dwarf plants, 20 cm tall, to giants up to 8 m tall.

The generic name is from the Latin equus (‘horse’), and seta, which has several meanings, including ‘rough’, ‘brush’, or ‘hair’. The latter word can refer to the rough, silica-containing stems of these plants, but together with equus, the word means ’horse hair’. With a bit of imagination, a bunch of drying stems do resemble a horsetail.

 

It is very common in humid meadows, where it often forms large colonies, which are much feared among farmers, as it is toxic to grazing animals, causing lack of coordination in horses, and lameness in cattle and sheep. In many places it is regarded as an invasive.

Marsh horsetail belongs to the group of horsetails, in which the sporangia are clustered in so-called strobili at the tip of the stem.

 

 

 

 

 

 

 

 

The nominate subspecies is native to the Caucasus, Turkey, Syria, Lebanon, and Bulgaria, whereas small populations of subspecies baeticum are distributed in south-western Spain and Portugal.

In 1763, Pontic rhododendron was introduced to Britain as an ornamental, and it was also planted as cover for game birds. It quickly became naturalized, spreading by suckers on the tips of the branches. Today, in England, Wales, and Ireland, it is a widespread menace, which has colonized numerous hillsides, moorlands, and shady woodlands, often replacing local plant species.

Many pictures, depicting other rhododendron species, may be seen on the page Plants: Rhododendrons.

 

 

 

 

 

 

The specific name means ‘wax-bearing’, referring to the tallow, which coats the seeds. Candles and soap are made from this wax, and in the Far East, the leaves are used in traditional medicine for treating boils. The sap and leaves are reputed to be toxic, and decaying leaves from the plant are toxic to other plants, inhibiting their growth.

Because of the tallow, this tree was introduced into the United States in the 1700s, and in the 1900s, it was widely planted along the Gulf Coast by the U.S. Department of Agriculture, in an attempt to establish a soap-making industry. However, it soon spread beyond control and is today regarded as a serious pest in south-eastern U.S., which expels native plant species. It is also regarded as invasive in India and Australia, and in Taiwan, despite being indigenous here.

In winter, the leaves of Chinese tallow-tree turn various gorgeous shades of red, varying from orange to wine-red. A collection of pictures, depicting this foliage, is shown on the page Autumn.

 

 

 

 

 

 

 

 

It is possibly a native of India, but at an early stage, it was introduced to many other countries, and today it has a pan-tropical and -subtropical distribution. In many areas, including Belize, West Indies, United States, Hawaii, and Polynesia, it is proclaimed an invasive weed.

The role of crab’s eye in folklore and medicine is described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

The role of common broom in folklore and medicine is described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

 

 

 

 

White leadtree is a prolific species, forming dense growths, often dispelling native vegetation. It is regarded as an invasive in numerous countries, including Taiwan, Hong Kong, several Pacific islands, northern Australia, southern United States, Puerto Rico, and parts of Europe and South America. By the Invasive Species Specialist Group (IUCN) it is considered to be among the world’s one hundred worst invasive species.

 

 

 

 

 

 

 

 

 

A native of western North America, the large-leaved lupine is a pretty garden plant, which readily escapes cultivation, forming large growths. It is regarded as an invasive species in many countries, including New Zealand, Finland, Norway, Switzerland, Czech Republic, and Lithuania.

 

 

 

 

 

 

 

Kudzu is much utilized in Chinese traditional medicine, described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

To some extent, its spreading can be controlled by the gorse spider mite (Tetranychus lintearius) and the gorse seed weevil (Exapion ulicis).

In English, the earliest known use of the word ulex is from 1753. It was mentioned by Roman naturalist Pliny the Elder (23-79 A.D.), when he described gold mining in north-western Iberia. Thus, the name Ulex may allude to the golden-yellow flowers of members of the genus.

A close relative, the western gorse (U. gallii), is described on the page In paraise of the colour yellow.

 

 

 

 

 

 

 

 

It is mostly a small tree, but may sometimes reach a height of 35 m. The bark is brown with narrow vertical or slanting grooves. The leaves are long-stalked, dark green, to 50 cm long, twice or thrice pinnate, with ovate or elliptic leaflets, to 7 cm long, margin toothed. The flowers are star-shaped, pink or lilac, to 1.8 cm across. They are arranged in clusters, growing from the leaf axils. The fruit is a drupe, about 8 mm across, light yellow at maturity, often hanging on the tree all winter, unless they are eaten by birds. They are poisonous to humans, but the birds are not affected.

The specific name stems from Persian azad dirakht, meaning ‘noble tree’.

The pictures below are all from Taiwan, where this species is commonly planted as an ornamental tree.

 

 

 

 

 

 

 

 

As its name implies, fibres of paper mulberry were formerly utilized to produce paper, and in parts of the Pacific, cloth is still made from the bark. The wood is used for making furniture and utensils, and the roots can be used as rope. The orange fruit is fleshy and edible, and the leaves can also be eaten when cooked. Fruit, leaves, and bark were formerly used in traditional medicine.

In the United States, paper mulberry was introduced as a fast-growing shade tree, but due to its vigorous growth it soon began to displace native species, and today it is considered to be an invasive in the south-eastern states. In Pakistan, it is regarded as one of the worst weeds, and it is a highly significant invasive plant on the pampas of Argentina. It is also one of the most dominant invasive species in forests of Ghana and Uganda.

 

 

 

 

 

 

 

 

 

 

 

 

 

The family name is derived from Onagra, the original name of evening-primroses (today called Oenothera). The term Onagra was first used in botany in 1587, meaning ‘(food) of onager’, an Asiatic species of wild ass (Equus hemionus). It is most odd that this name was applied to evening-primroses, which were originally purely American plants.

 

The genus was named by Swedish naturalist Carl Linnaeus (1707-1778) in honour of German botanist Christian Gottlieb Ludwig (1709-1773). However, it seems that Ludwig was not too happy about this honour. Maybe the flowers of this genus were not pretty enough? Or he didn’t like aquatic plants to be named after him?

 

The origin of this species is not clear, but today it is a very widespread weed of rice fields and wetlands in tropical and subtropical areas around the world.

The specific name refers to the likeness of its leaves to those of hyssop (Hyssopus officinalis), of the mint family (Lamiaceae).

 

 

 

 

 

 

 

It closely resembles water primrose-willowherb (L. peploides), which, however, usually has elliptic or ovate leaves and 5 overlapping petals.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In western United States it has been extensively planted as a means to control soil erosion, and as a biomass plant, but it often escapes and has become highly invasive in numerous places, especially along rivers, where it often displaces the natural vegetation.

The generic name is the classical Latin term for several reed species with stiff, bamboo-like stems. The specific name is the Ancient Greek name of this species.

 

 

 

 

 

In former days, wild oat was so numerous that in certain areas it would lower the yield of crops by 40%. In Denmark, it was declared an outlaw in 1956, to be “removed from all cultivated and un-cultivated areas by the owner or the user.” Before the introduction of chemical herbicides, the plants had to be removed by hand, which was a very time-consuming task. An advantage was that wild is often taller than the surrounding crop, making it relatively easy to spot.

Today, wild oat is still is a serious pest in many countries, and as it is highly adaptable to various environments, it has become naturalized in numerous places. It is regarded as being among the world’s worst agricultural weeds. (Sources: D.P. Jones (ed.) 1976. Wild oats in world agriculture. An interpretative review of world literature. Agricultural Research Council. London; and L.G. Holm et al. 1977. The World’s Worst Weeds. Distribution and Biology. University Press of Hawaii)

 

 

 

 

 

It is native to northern and eastern Africa, Arabia, and the Near East, but has become naturalized in many other places, and is often regarded as an invasive species, which is a threat to native species. It also tends to increase the risk of wildfires, to which it is well adapted, thus posing a further threat to certain native species.

 

 

 

 

 

Whatever its origin may be, it has been accidentally introduced to most warmer parts of the world and is regarded as an invasive in a number of countries, including Australia, Korea, Thailand, Cambodia, and India.

It is a common weed in sugarcane and rice fields, which is a serious problem, as it is a host of a number of rice insect pests, including white-backed planthoppers (Sogatella furcifera and Sogatodes pusanus), rice bug (Leptocorisa oratorius), rice ear-cutting caterpillar (Mythimna separata), cereal thrips (Haplothrips ganglbaurei and Chirothrips mexicanus), and others.

The generic name refers to the goddess Chloris, in Greek mythology the protector of plants. The specific name is Latin, meaning ‘bearded’, alluding to the inflorescence.

 

 

 

 

 

Pampas grass is very adaptable, and a single plant can produce over one million seeds during its lifetime. As a result, it has become invasive in many places, including New Zealand, Florida, California, Hawaii, South Africa, and Spain.

 

 

 

 

 

Indian goosegrass, which is possibly a native of warmer areas of Africa and Asia, is considered a “serious weed” in at least 42 countries. Besides being an agricultural weed, it also invades forests margins, grasslands, marshes, river banks, and road sides. Currently, it is listed as invasive in several countries in Europe, Asia, Central and South America, and the Caribbean, and on many islands in the Pacific Ocean. (Sources: cabi.org/isc/datasheet/20675; L.G. Holm et al. 1977. The World’s Worst Weeds. Distribution and Biology. University Press of Hawaii)

 

 

 

 

 

The medical usage of couch grass is described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

It is native from Mauritania and Sudan southwards to the Cape Province, and is also found in Madagascar and southern Arabia. However, it has been introduced as an ornamental, or unintentionally, to many other parts of the world. It has been declared an invasive plant in Mexico, United States, Australia, the Dominican Republic, and French Polynesia.

The generic name may be derived from Ancient Greek melinos (‘ashy-grey’), perhaps alluding to the colour of the inflorescences, before they turn snow-white. The specific name is Latin, meaning ‘low’, probably referring to the growth of tufts.

 

 

 

 

 

The stems vary in height, from 20 cm to 1 m, erect or arching. Leaves are to 30 cm long and 6 mm wide, flat or with a keel. The inflorescence is a loose, spreading panicle, to 20 cm long, spikelets very small, to 3 mm long. It readily spreads by its large, branching rhizomes, which are pointed, giving rise to the name torpedograss. By Mississippi State University, it is referred to as “one of the world’s worst weeds. (…) When fully matured, torpedograss can grow up to 3 feet tall and form dense monotypic stands that out compete native species and lead to a loss of diversity and overall ecological health.”

The generic name is the classical Latin name of foxtail millet (Setaria italica). The origin is uncertain, probably either from panis (‘bread’ or ‘loaf’), or from panus (‘an ear of millet’). The specific name is Latin, meaning either ‘creeping’ (which is a very bad name for this tall grass), or ‘unexpected’, ‘suddenly’, which may allude to it popping up everywhere.

 

 

 

 

 

 

 

 

 

 

 

 

 

Variegated Japanese knotweed is listed by the World Conservation Union as one of the world’s worst invasive species.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This pioneer plant grows in open forests, shrubberies, and fallow lands, especially on nitrogen-rich soils. It is distributed in central and southern Europe, North Africa, and the Middle East, eastwards to Afghanistan. Elsewhere, it is widely cultivated, often escaping to form naturalized growths. In New Zealand, it has been declared an unwanted organism. In the Alps and the Pyrenees, it may be encountered up to elevations around 1,300 m.

It contains the toxic protoanemonin, which may cause reddening and itching of the skin. In the past, beggars smeared juice of the leaves on the skin to cause ulcerations, which might arouse pity in people. In Tuscany, spring sprouts were formerly used in a certain kind of omelettes, called vitalbini, which was maybe not so wise due to its toxicity.

Baskets were produced from the tough stems. In the Alps, in former days, children would smoke dry stems as cigarettes.

The specific name is the Italian name of the plant. In England, the name traveller’s joy was given in allusion to the profusion of pleasant feathery seedheads of this plant in the dark months leading up to Christmas. The name old man’s beard also refers to the seedheads. An old German folk name was Teufelzwirn (‘devil’s twine’), referring to its toxicity.

 

 

 

 

 

 

 

The specific name is from the Latin acer (’sharp’), referring to its bitter taste. All buttercup species are poisonous, for which reason they are avoided by grazing animals, as seen in the picture below.

 

 

 

 

 

Incidentally, the name lesser celandine is a misnomer. The greater celandine (Chelidonium majus) is a plant of the poppy family (Papaveraceae), presented on the page Plants: Plants in folklore and poetry. In the early days of classification, certain botanists thought that the plant, which is today called Ranunculus ficaria, was related to greater celandine, naming it Chelidonium minus, and in English lesser celandine. For some reason or other, both English names of these entirely unrelated plants stuck.

 

 

 

 

 

 

It has been widely planted in Europe, and also in South Africa. It readily grows in shady places, thus being able to spread easily. In many European countries it has become an invasive species, and in habitats like moors and grasslands it is a threat to indigenous plant species. Leaves and bark are toxic, and in South Africa it is regarded as a major cause illnesses in livestock.

 

 

 

 

 

 

 

However, it readily escapes cultivation, forming dense thickets along roads, in abandoned fields, on grazing grounds and prairies, and in open forests. In numerous places, it has become a serious pest, spreading beyond control and expelling native plant species. Today, it is regarded as an invasive plant in many countries.

 

 

 

 

 

 

 

Today, it is abundant on all North European and New England beaches, where it is considered a serious pest, which expels natural vegetation.

 

 

 

 

 

 

 

 

 

 

 

 

 

An example of the effective spreading of sycamore maple is seen in nature reserve Vorsø, Horsens Fjord, Denmark, where former fields were abandoned in two steps, in 1928 and in 1978. In both cases, thousands of maple seeds, stemming from a few trees in plantations at the edge of the fields, were spread by the wind. The succession of these maple forests is described in depth on the page Nature Reserve Vorsø: Expanding wilderness.

 

 

 

 

 

 

 

This species is widely distributed in tropical and subtropical Africa and Asia, and has also become naturalized in many other parts of the world, often covering huge areas. In New Zealand, where it is considered a pest, trading of its seeds is prohibited.

The medical usage of balloon vine is described on the page Plants: Plants in folklore and poetry.

 

 

 

 

 

 

 

 

Stem, leaves, and root are much utilized in Chinese herbal medicine, chiefly as an invigorator of the blood circulation, but also as an anti-inflammatory in swellings and wounds, for shingles, tuberculosis, and toothache, and as a diuretic.

The generic name is derived from Ancient Greek lygos (‘flexible twig’), originally from Proto-Indo-European lewg (‘to bend’ or ‘to twist’), and eidos (‘appearance’), thus ‘looking like a flexible twig’.

 

 

 

 

 

 

 

 

 

 

 

Dutch Elm disease is spread by elm bark beetles of the genera Scolytus and Hylurgopinus. It is generally believed that the disease originated in Asia, but was accidentally introduced to Europe and North America, where most native elm species had no resistance against the disease.

This disease is described in depth on the page Nature Reserve Vorsø: Dutch Elm disease on Vorsø.

 

 

 

EE Ran Ranunculus acris_018