Urban plant life
Railroad creeper (Ipomoea cairica, Convolvulaceae), creeping along barbwire, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
This spreading pellitory-of-the-wall (Parietaria judaica, Urticaceae) has sprouted in a hole on a house wall, Sultanahmet, Istanbul, Turkey. (Photo copyright © by Kaj Halberg)
Mexican primrose-willowherb (Ludwigia octovalvis, Onagraceae), growing along the Han River, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
This Asiatic dayflower (Commelina communis, Commelinaceae) has sprouted in a crack along a house wall, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Withered peacock-plume grass (Chloris barbata, Poaceae) is often very decorative. These specimens are illuminated by the morning sun against a dark wall in the city of Taichung, Taiwan. The small plants are lantern tridax (Tridax procumbens), described below under Asteraceae. (Photo copyright © by Kaj Halberg)
Although fungi are not plants, I have included them on this page.
Coprinus comatus Shaggy ink-cap
Easily identified by by the pure white, tall, cylindric cap with tiny, spread-out scales. Initially, the cap is closed around the stem, later slightly spread out. The gills are white at first, later rose-coloured, finally becoming a black, ink-like liquid. After spreading the spores, it quickly disintegrates.
Shaggy ink-cap is rather common in nutritious places, including fertilized grass fields and lawns, around farms, along roads, etc. It is present from summer to late autumn, often in large congregations. When young, it is edible and quite tasty.
These shaggy ink-cap have sprouted in an unusual spot, in a crack along a pavement in the town of Nyborg, Denmark, together with white goosefoot (Chenopodium album), annual meadow grass (Poa annua), and common knotgrass (Polygonum aviculare). (Photo copyright © by Kaj Halberg)
Shaggy ink-cap, as it is most commonly encountered: in a grazed field. – Jutland, Denmark. (Photo copyright © by Kaj Halberg)
Amaranthaceae Amaranth family
Amaranthus viridis Slender amaranth
The native area of this species, also known as green amaranth, is unknown, and today it is distributed in all warmer areas of the world.
Leaves, as well as seeds, are eaten in many parts of the world. In Australia, this plant was also a source of food during the 19th Century. In 1889, botanist Joseph Maiden (1859-1925) wrote: “It is an excellent substitute for spinach, being far superior to much of the leaves of the white beet sold for spinach in Sydney. Next to spinach it seems to be most like boiled nettle leaves, which when young are used in England, and are excellent. This amarantus should be cooked like spinach, and as it becomes more widely known, it is sure to be popular, except amongst persons who may consider it beneath their dignity to have anything to do with so common a weed.” (Source: T. Low, 1985. Wild Herbs of Australia & New Zealand. Angus & Robertson)
In India, slender amaranth is utilized in traditional Ayurvedic medicine.
Amaranth species are also known as pigweeds. In his delightful book All about Weeds, Dover Publications (1974), American botanist Edwin Spencer (1881-1964) says about a close relative, A. retroflexus:“One of the most robust, devil-may-care weeds is the pigweed. ‘Careless weed’ is another of its common names, and it comes by this name honestly enough. In good rich soil, it cares for nothing. Wind, hail, fair weather and foul are all the same to the pigweed. Nor does it care what plants are its competitors. It can usually shoulder our any plant within reach, and it has a considerable reach. The name pigweed, however, has no reference to the piggish nature of the plant. It refers to the gustatory pleasure the weed affords pigs. Hogs will leave their corn to feast on pigweeds. In spite of its bristly appearance (it always reminds one of a boisterous young sailor with a week’s growth of sandy beard on his face and his cap on the side of his head), the leaves are tender, and if the smacking of lips and satisfied grunts mean the same thing to pigs that they do to Man, the weeds must be delicious.”
In Taiwan, slender amaranth is very common in cities, especially in fallow areas, and along roads and embankments. These pictures are all from Taichung.
(Photos copyright © by Kaj Halberg)
Celosia argentea Silver cockscomb
Like the slender amaranth, the native area of this species, also called feathery amaranth, is unknown, and today it is found in most tropical and subtropical areas of the world. It is regarded as an invasive plant in numerous countries, including India, Japan, Ecuador (Galapagos Islands), Fiji, Taiwan, and the United States.
Silver cockscomb is described in depth on the page Plants: Plants in folklore and poetry.
Silver cockscomb is abundant in Taiwan, also in cities, where it often grows in abandoned plots, in this case in Taichung. Downy bur-marigold (Bidens pilosa, see below), likewise an invasive species, is also seen in the picture. (Photo copyright © by Kaj Halberg)
Silver cockscomb, growing in an abandoned parking lot, Taichung. (Photo copyright © by Kaj Halberg)
In this picture, silver cockscomb completely covers the bottom of a drainage canal in Taichung. (Photo copyright © by Kaj Halberg)
Anacardiaceae Sumac family
Sumacs are a genus of c. 35 species, distributed in subtropical and temperate areas, especially around the Mediterranean, and in Asia, Australia, and North America. Other species, which were formerly placed in Rhus, have now been transferred to the genus Searsia, others to Toxicodendron, including poison ivy and poison oak, described on the page Autumn.
The word sumac is derived from Ancient Syriac summaq (‘red’), referring to the red fruits of the genus. They have an acrid taste and are used as a spice. In North America, the fruits of staghorn sumac (Rhus typhina) are soaked in cold water to make ‘pink lemonade’, a refreshing beverage, rich in vitamin C.
Rhus coriaria Elm-leaved sumac
This species is also known by other names, including tanner’s sumac and Sicilian sumac. It is native to areas around the Mediterranean, eastwards to Iran. The dried fruits are crushed and used as a spice, which, together with other spices, form a mixture called za’atar. Leaves and bark contain tannic acid and were formerly used in leather tanning, hence the specific name, of the Latin coriarium (‘leather’, ‘tanning’). Various parts of the plant yield red, yellow, black, and brown dyes. Oil from the seeds are utilized to make candles.
Elm-leaved sumac is very common in Turkey. This one has taken root on the wall of an abandoned house in Sultanahmet, Istanbul. (Photo copyright © by Kaj Halberg)
Aegopodium podagraria Goutweed
As far back as Ancient Rome, and throughout the Middle Ages, young leaves of goutweed were utilized as a vegetable, much as spinach is used. The generic name is from the Greek aix, genitive aigos (’goat’), and podion, diminutive of pous (’foot’), thus ‘little goat-foot’, referring to the shape of the leaves. According to the Doctrine of Signatures, Our Lord had shaped the plants, so that humans were able to discover what ailments they could be used for. Therefore, goutweed must be an effective remedy for gout. Medicinally, however, there is no basis for this assertion. It was also used as a laxative.
Goutweed is native to southern Europe and western Asia, but was introduced as a garden plant to northern Europe as early as the Middle Ages. It has also been accidentally introduced to North America, and almost everywhere it has become a most annoying garden weed.
In this picture, goutweed is growing out through a beech hedge alongside a pavement. – Jutland, Denmark. (Photo copyright © by Kaj Halberg)
Goutweed as a garden weed, Funen, Denmark. (Photo copyright © by Kaj Halberg)
Apocynaceae Dogbane family
Catharanthus roseus Madagascar periwinkle
This pretty plant is native to Madagascar, but is widely cultivated in warmer areas as an ornamental and sometimes escapes cultivation. It is also widely used as a medicinal plant, as it is a source of drugs, used in the treatment of cancer. Previously, it was included in the genus Vinca.
Madagascar periwinkle, growing in a crack in a concrete wall along a drainage canal, Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
A huge, worldwide genus, counting between 200 and 400 species. Besides mugwort, common names of these plants include wormwood and sagebrush. The genus is presented in depth on the page Plants: Plants in folklore and poetry. A picture, depicting lance-leaved mugwort (A. lancea), may be seen under Ixeridium laevigatum (below).
Artemisia vulgaris Common mugwort
This plant is native to the major part of Temperate Europe and Asia, and also to North Africa and Alaska. In other areas of North America, it has become naturalized. Originally, it was restricted to dry grasslands and sandy beaches, but when farming was introduced, it readily spread to fields, and today it is regarded as a noxious weed.
In China, this species is sometimes used as a substitute for A. argyii to make moxa, which is much utilized as a healer in traditional Chinese medicine.
Common mugwort, growing near a canal in Copenhagen, Denmark. (Photo copyright © by Kaj Halberg)
Bidens pilosa Downy bur-marigold
This pan-tropical and -subtropical weed, of unknown origin, has become a pest in numerous places, expelling native species. One isolated plant can produce over 30,000 hooked seeds, which are readily spread by sticking to animals’ furs, socks, trousers, etc.
This method of seed dispersal has given it names like beggar-ticks, stickseed, farmer’s friend (ironic!), needle grass, Spanish needles, stick-tight, cobbler’s pegs, Devil’s needles, and Devil’s pitchfork. Other names include blackjack and hairy bidens.
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.”
Downy bur-marigold 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, this species is not only a troublesome weed, but also has medicinal properties. In traditional Chinese medicine, it is 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.
In Taiwan, downy bur-marigold is extremely common, often covering huge areas, including in cities, where it pops up everywhere, as is obvious from the pictures below, all from Taichung.
This downy bur-marigold has sprouted in a drainage canal. (Photo copyright © by Kaj Halberg)
This one is growing up a fence. (Photo copyright © by Kaj Halberg)
Here, a specimen has taken root between two road dividers. (Photo copyright © by Kaj Halberg)
These pictures show the characteristic fruits of downy bur-marigold. The hooked seeds will cling to almost anything. (Photos copyright © by Kaj Halberg)
This huge genus, comprising about 200 species, is distributed in the Northern Hemisphere and Africa, with the core area around the Mediterranean. The generic name is derived from the Greek krepis (‘slipper’ or ‘sandal’), according to some authorities referring to the shape of the fruit.
Crepis capillaris Smooth hawk’s-beard
A widespread plant, native to the major part of Europe, eastwards to the Ural Mountains and the Caucasus, but widely introduced elsewhere, including North America, the northern Andes, South Africa, and Australia. It grows to 60 cm tall, with numerous pale yellow flowerheads to 1.5 cm across.
Smooth hawk’s-beard, growing in a crack in a house wall, Jutland, Denmark. (Photo copyright © by Kaj Halberg)
This genus contains c. 115 species, distributed mainly in tropical and subtropical areas of Africa and Asia.
Emilia sonchifolia Lilac tasselflower
Lilac tasselflower may grow to 70 cm tall, but is often much smaller. It is probably native to South and East Asia, but is today widespread in tropical and subtropical regions around the world.
This plant is also known as Cupid’s shaving brush, named for Cupid, the Roman god of desire, eroticism, and affection, alluding to the tiny flowerheads, which resemble miniature shaving brushes. The specific name is derived from the Greek sonchos, the ancient name for sow-thistles, and the Latin folium (‘leaf’). The leaves of this plant often resemble those of Sonchus oleraceus (see below). However, they vary tremendously, from lyrate and pinnatifid to almost entire.
Lilac tasselflower, photographed in Taiwan, where this species is very common, also in cities, in this case Taichung. (Photos copyright © by Kaj Halberg)
Erigeron canadensis Horsetail fleabane
This plant is also known as Canadian fleabane, and some authorities regard it as belonging to the genus Conyza. It is native to North America and parts of Central America, but has been accidentally introduced to large parts of the world. In many places it has become a serious pest, especially in Europe and Australia, but also in its native North America. It prefers to grow in undisturbed areas and is particularly troublesome in newly established plantations, where it is able to resist herbicides, growing to 3 m tall, thus depriving planted species of nutrients and sunlight.
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, growing along a street in the city of Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
This horsetail fleabane, observed in a graveyard in Taichung, is almost 2 m tall. (Photo copyright © by Kaj Halberg)
Gnaphalium uliginosum Marsh cudweed
Marsh cudweed, sometimes called brown cudweed, is native to Europe and northern Asia, and it has been accidentally introduced in North America, where it is found in the northern half of the continent.
The natural habitat of this plant is humid areas, such as water-logged fields, but it is also able to thrive in drier areas, including city streets. In Russia, it has been used in folk medicine to treat high blood pressure.
Marsh cudweed (the greyish-green plants), growing among cobble stones on a sidewalk, Jutland, Denmark, together with annual meadow-grass (Poa annua) and greater plantain (Plantago major, see Plantaginaceae below). (Photo copyright © by Kaj Halberg)
The basal leaves of this species are very variable, mostly with rather large lobes, but sometimes being almost entire, whereas the stem leaves are mostly linear and rather narrow. The yellow flowerheads are up to 1 cm across. It is distributed in Japan, China, Taiwan, Indochina, the Philippines, and Indonesia, growing in forests, shrubberies, and grasslands, up to an elevation of about 600 m.
In Taiwan, Ixeridium laevigatum is often encountered in urban areas. In this picture, it grows beneath a tree on a sidewalk in Taichung, together with lance-leaved mugwort (Artemisia lancea). (Photo copyright © by Kaj Halberg)
Ixeris chinensis Rabbit milkweed
This plant is easily identified by its mostly linear, rather narrow leaves and pale yellow flowerheads, to 2 cm across. It is distributed from south-eastern Siberia southwards through China, Korea, Japan, and Taiwan to Southeast Asia, growing commonly in a variety of habitats, including grasslands, forest margins, shrubberies, riverbanks, field margins, wastelands, and roadsides, up to an elevation of about 4,700 m.
As these pictures show, rabbit milkweed may sprout in small cracks in roads and sidewalks, and along house walls. – Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
Matricaria discoidea Disc mayweed
Disc mayweed is native to North America and north-eastern Asia, southwards to Hokkaido, Japan. Today, however, it has been accidentally introduced to most other areas of the world, where it is a common weed, growing in open areas. Other names of the plant include wild chamomile and pineapple weed, due to its chamomile- or pineapple-like smell, when crushed.
Disc mayweed, growing in a crack along a gutter, Jutland, Denmark. The white object is a bird feather. (Photo copyright © by Kaj Halberg)
This genus, popularly called squarestems, contains about 37 species, native to Africa, Asia, Oceania, and the Americas. The generic name is from the Greek melas (‘black’, ‘dark’), and anthos (‘flower’), referring to the black anthers of this genus.
This creeping plant, which was formerly named Wedelia prostrata, has tiny yellow flowerheads. It is native to Japan, Korea, southern China, Taiwan, Thailand, and Vietnam, where its original habitats are dunes and sandy seashores. However, it has adapted to other places, including roadsides and grassy areas.
In Taiwan, Melanthera prostrata is a common city plant, often growing in cracks along sidewalks. These were photographed in Taichung. (Photos copyright © by Kaj Halberg)
A large growth of Melanthera prostrata, climbing up a long-term parked bicycle, Taichung. (Photo copyright © by Kaj Halberg)
Members of this American genus, which contains about 12 species, are commonly known as feverfew, not to be confused with an Old World plant with the same name, Tanacetum parthenium, which is presented on the page Plants: Plants in folklore and poetry. The generic name is a Latinized version of the Greek parthenos (‘virgin’), or maybe parthenion, which was the name of an unknown plant in Ancient Greece.
Parthenium hysterophorus Santa Maria feverfew
The leaves of this plant, which may grow to a height of about 120 cm, very much resemble those of some species of Artemisia (see above), but its flowerheads are more flattened, and pure white. In America, it has a number of other names, including bitterweed, carrot grass, congress grass, false chamomile, false ragweed, and white-top.
Santa Maria feverfew is native to large parts of the Americas, from southern United States southwards to Mexico, the Caribbean, and northern South America. However, it has been spread to virtually all warmer areas of the world and has become naturalized in many places, ranging from fields and grasslands to roadsides, fallow plots, and along railroads, usually below 1,500 m altitude. It is regarded as an invasive in Kenya, Uganda, and Tanzania.
The specific name is from the Greek hystera (‘womb’) and phoros (‘bearing’), maybe alluding to the shape of the flowerheads.
This plant should be handled with caution, as it may cause dermatitis and respiratory malfunction in humans, and, if eaten by livestock, it may cause udder disease.
In these pictures, Santa Maria feverfew grows along busy streets in Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
This genus, comprising about 100 species, is widely distributed in the entire Old World, and has also become widely naturalized in the New World.
The generic name is a Latinized form of the Greek sonchos, the ancient name for sow-thistles.
Sonchus asper Prickly sow-thistle
A stout plant, which may grow to 1.2 m tall, but is often much lower. The stem is often reddish. Leaves are extremely variable, obovate, spatulate, or elliptic, to 13 cm long and 5 cm wide, entire or irregularly divided, base eared and strongly recurved, clasping the stem, margin heavily spiny. Flowerheads relatively few, to 2.5 cm across, in an open terminal cluster. Ray florets numerous, bright yellow, disc florets absent.
This species presumably originates from the Mediterranean region, but has become naturalized in most parts of the world. In Nepal, a paste of the plant is applied to wounds and boils. It is also collected for fodder, and tender parts are cooked as a vegetable.
In the picture below, a specimen is growing in front of a tombstone in the Assistens Cemetery, Copenhagen, placed in memory of Thorkild Weiss Madsen, who was active in the alternative-lifestyle area of Christiania. (More about this area is found on the page Culture: Folk art around the world.) The stone is formed as a runic stone with a carved dragon and the following text (approximate translation): ”This stone was erected in memory of Thorkild by his wife and daughter. The good boy Eric the Red carved the runes.”
(Photo copyright © by Kaj Halberg)
Sonchus oleraceus Common sow-thistle
This species is native to Europe and western Asia, but has been spread to most other areas of the world. It is regarded as an invasive plant in many countries, including Australia, where it is a serious problem in crops. It is easily identified by its slightly prickly, deeply divided leaves.
The specific name is derived from the Latin oleris, meaning ‘edible’. Young leaves can be eaten as salad or cooked like spinach. The common name refers to the fact that pigs like to eat this plant, and to the leaves, which resemble young thistle leaves.
Common sow-thistle is very common in Taiwan. This picture shows a large growth in the city of Taichung. The white flowers are downy bur-marigold (Bidens pilosa, see above). (Photo copyright © by Kaj Halberg)
Common sow-thistle, growing in a city park, Taichung. This specimen is probably a hybrid with prickly sow-thiste (S. asper), as the leaves of common sow-thistle are usually much less prickly. However, the pointed ‘ears’ at the nodes indicate common sow-thistle.(Photo copyright © by Kaj Halberg)
This common sow-thistle has taken root along a house wall in the town of Rønne, Bornholm, Denmark. (Photo copyright © by Kaj Halberg)
This plant is native from Turkey eastwards to the Caucasus and Central Asia. The well-known garden plant feverfew (T. parthenium) possibly evolved through selection from this species. Its leaves are dark green or grey-green, with a pointed outline, whereas they are pale green and has a rounded outline in feverfew. Otherwise they are very similar.
The medicinal properties of feverfew are discussed on the page Plants: Plants in folklore and poetry.
Tanacetum partheniifolium is very common in Istanbul, even on buildings. (Photos copyright © by Kaj Halberg)
Taraxacum officinale Dandelion
Dandelion is ubiquitous in Europe, including in cities, where it readily grows in cracks and between flagstones. It is dealt with in detail on the page Plants: Plants in folklore and poetry.
In these pictures from Copenhagen, Denmark, dandelion grows among wood chips, strewn along a street (top), and outside the Carlsberg Breweries. (Photo copyright © by Kaj Halberg)
Tridax procumbens Lantern tridax
This small composite, which is native to Tropical America, has been introduced to most warmer areas of the world and has become naturalized in many places.
Lantern tridax is extremely common in Taiwanese cities, sprouting in cracks everywhere and often covering large areas. The pictures below are all from Taichung.
(Photos copyright © by Kaj Halberg)
Here, lantern tridax has sprouted in a crack in a concrete wall along the Han River. (Photo copyright © by Kaj Halberg)
Lantern tridax, growing near a metal sheet wall. A species of aster or everlasting is seen among the grass leaves. (Photo copyright © by Kaj Halberg)
In this picture, lantern tridax has sprouted on a grass-clad grave. The plant with white flowerheads is downy bur-marigold (Bidens pilosa, see above). (Photo copyright © by Kaj Halberg)
Youngia japonica Oriental false hawksbeard
The stem of this plant, which is also known as Japanese hawksbeard, is usually tall, erect, and unbranched, with numerous small, yellow, terminal flowerheads, to 8 mm across. The basal leaves are quite broad, more or less hairy, and mostly deeply lobed or pinnately divided. It is native to Asia and Australia, but has spread to most warmer areas of the world. It is common in disturbed areas, wastelands, roadsides, abandoned pastures, lawns, cultivated fields, and forest margins.
Oriental false hawksbeard thrives under tree cover, and in cities it is mostly found in parks. In the upper picture, it forms a large growth in Tunghai University Park, Taichung. (Photo copyright © by Kaj Halberg)
Blechnaceae Chain-fern family
Blechnum orientale Oriental hard fern
This large fern, with fronds sometimes reaching a length of 2 m, is distributed from the Indian Subcontinent eastwards to southern China, Taiwan, and southern Japan, and thence southwards through Southeast Asia to New Guinea, Australia, and islands in the western Pacific. Elsewhere, it is cultivated as an ornamental, and plants are sometimes harvested from the wild to be used for food or medicine.
This oriental hard fern is clinging to a crack in a wall along a drainage canal, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Brassicaceae Mustard family
Capsella bursa-pastoris Shepherd’s-purse
Shepherd’s-purse, which is native to western Asia and Europe, has become naturalized almost worldwide in temperate and subtropical areas. It is also called shepherd’s bag, shepherd’s scrip, shepherd’s sprout, lady’s purse, witches’ pouches, rattle pouches, case-weed, pick-pocket, pick-purse, blindweed, pepper-and-salt, poor man’s pharmacettie, and mother’s heart. Most of these names, as well as the specific name, refer to the shape of the fruits, or siliques, which are flat and triangular, resembling an old-fashioned bag or purse.
An Irish name of the species, clappedepouch, was likewise given in allusion to the long-stalked siliques, which resemble a beggar’s cup. In the old days, lepers would ring a bell, or a clapper, receiving their alms in a cup at the end of a long pole, to avoid people being infected.
The medical usage of this species is described on the page Plants: Plants in folklore and poetry.
Shepherd’s-purse, growing in a crack along a sidewalk in Denmark. (Photo copyright © by Kaj Halberg)
Large growth of shepherd’s-purse in Tunghai University Park, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Lepidium virginicum Virginian peppercress
The common names of this species, which also includes least pepperwort, stem from the fact that all parts of this plant have a peppery taste. It is a native of North America, from southern Canada southwards to Mexico, but has been widely introduced to many other countries. It grows in open, drier places, and has readily adapted to a life in cities.
This Virginian peppercress has sprouted in a crack in an abandoned parking lot in the city of Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Sisymbrium officinale Hedge mustard
An erect plant, to 80 cm tall, branches often growing at a right angle from the stem. The small, yellow flowers develop into long fruits, sitting close to and parallel to the stem.
This species grows in wasteland and fields, and along roads, also in towns. It is native to Europe and North Africa, but has been spread to most cooler areas of the globe, sometimes cultivated for its edible leaves and seeds.
It was formerly widely used in traditional medicine, reflected in the specific name, which means ‘sold in offices’, i.e. pharmacies. In Ancient Greece, it was believed that the plant was an antidote to all poisons. In his Complete Herbal, English herbalist Nicholas Culpeper (1616-1654) writes: ”It is good for all diseases of the chest and lungs, hoarseness of voice (…) The juice, made into a syrup with honey or sugar, is no less effectual for all other coughs, wheezing and shortness of breath. The seed is held to be a special remedy against poison and venom.”
“It is named by the French the ‘Singer’s Plant,’ it having been considered up to the time of Louis XIV an infallible remedy for loss of voice.” (Source: botanical.com)
Hedge mustard, growing at the edge of a street, Jutland, Denmark. (Photo copyright © by Kaj Halberg)
Cannabaceae Hemp family
Humulus japonicus Japanese hop
This plant is a native of the Far East, growing from Ussuriland, south-eastern Siberia, southwards through China, Korea, Japan, and Taiwan to northern Vietnam.
In the late 1800s, it was imported to the United States as an ornamental, and for use as an Asian tonic. However, it has escaped in many places, often covering large areas of open ground. The vines grow rapidly during the summer, climbing up and over everything in their path, often forming dense mats, which block light to plants underneath. It is invasive in riparian and floodplain habitats where it displaces native vegetation, prevents the emergence of new plants, and kills newly planted trees installed for streamside habitat restoration. (Source: invasive.org/alien/pubs/midatlantic/huja.htm)
In Taiwan, where Japanese hop is an indigenous species, it is very common, also in cities. The pictures below are from Taichung.
Japanese hop, creeping over scrapped machinery. (Photo copyright © by Kaj Halberg)
In this picture, it climbs along the rail of a bridge. (Photo copyright © by Kaj Halberg)
Humulus lupulus Common hop
This species is described in depth on the page Plants: Plants in folklore and poetry.
Hop, covering the door of an abandoned house, Funen, Denmark. (Photo copyright © by Kaj Halberg)
Caryophyllaceae Carnation family
Sagina procumbens Procumbent pearlwort
Spergularia rubra Red sand-spurrey
These small plants are native to Europe and Northern Asia, but have been accidentally spread to many other parts of the world. They are common weeds in fallow fields and along roads, and both have adapted to a life in cities.
In this picture from the town of Gudhjem, Bornholm, Denmark, red sand-spurrey (left) and procumbent pearlwort are growing in a crack on a sidewalk. (Photo copyright © by Kaj Halberg)
Commelinaceae Dayflower family
This genus has anywhere between 100 and 170 species, found in tropical and subtropical regions around the world. These plants are called dayflowers due to their flowers, which usually only live for one day.
When Swedish naturalist Carl Linnaeus (1707-1778) named this genus, he let the two showy blue petals of Commelina communis represent two Dutch botanists, Jan Commelijn and his nephew Caspar, whom he wished to honour.
Commelina communis Asiatic dayflower
This species is native to large parts of eastern Asia, from Ussuriland, south-eastern Russia, southwards through China, Korea, Japan, and Taiwan to the northern part of Southeast Asia and extreme eastern India. It has also been introduced to western Russia, south-eastern Europe, and eastern North America, where it has become invasive in several places.
In Chinese traditional medicine, the dried plant is utilized to treat a number of ailments, including sore throat, colds, oedema, bruises, and limited urination. A near relative, C. benghalensis, is eaten as a vegetable in Southeast Asia and Africa.
In this picture, and in a picture on top of this page, Asiatic dayflower is growing along a house wall in Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
This Asiatic dayflower is growing up through the wheels of long-term parked bicycles, Taichung. The plant to the right is paper mulberry (Broussonetia papyrifera, see below). (Photo copyright © by Kaj Halberg)
Convolvulaceae Morning-glory family
Many members of this family are presented on the page Plants: Morning-glories and bindweeds.
This small-flowered creeper is widespread in warmer areas of Asia, Africa, and Australia, growing along roads, on mountain slopes, and in other open areas, usually in dry places.
The taxonomy of the plant is not clear. Some authorities recognize only two species of small-flowered Ipomoea with heart-shaped sepals, I. plebeia and I. sinensis, regarding I. biflora as synonymous with either of the two. (Source: eflora of China)
Ipomoea biflora, climbing up the stem of a slender amaranth (Amaranthus viridis, see above), growing in an abandoned plot in Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
In this picture, Ipomoea biflora is climbing along barbwire, Taichung. (Photo copyright © by Kaj Halberg)
Ipomoea cairica Railroad creeper
This climber has many other common names, including coast morning-glory and mile-a-minute vine. It is believed to be a native of Tropical Africa, but is today very widely distributed in tropical and subtropical areas around the world. 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.
Railroad creeper is extremely common in Taiwan. The pictures below are all from Taichung. In the upper picture, the plant in the foreground is parasol-leaf tree (Macaranga tanarius), also called heart leaf or nasturtium tree, of the spurge family (Euphorbiaceae).
(Photos copyright © by Kaj Halberg)
Ipomoea nil Blue morning-glory
Flowers of this plant, also known as ivy-leaved morning-glory and Japanese morning-glory, are various shades of blue, with a white funnel. It may be told from similar species by the base of the calyx being hairy (clearly seen in the close-up photo below). It is thought to be a native of Mexico or Central America, but has been widely introduced elsewhere in warmer countries as an ornamental, or accidentally.
A form with pale blue flowers is very common in Taiwan, also in cities. In these pictures, plants are climbing up a house wall and fences, all in the city of Taichung. (Photos copyright © by Kaj Halberg)
Ipomoea obscura Obscure morning-glory
This species, also called small white morning-glory, can be identified by its small, heart-shaped leaves and the 2-3 cm wide, white flowers with a brownish throat. It is native to the southern half of Africa, tropical Asia, northern Australia, and some Pacific Islands, including Fiji, and has been introduced elsewhere as an ornamental, or accidentally.
Obscure morning-glory is very common in Taiwanese cities. These pictures are from Taichung.
In this picture, obscure morning-glory has sprouted in a crack in a concrete embankment along a drainage canal. (Photo copyright © by Kaj Halberg)
These plants are growing in cracks in an abandoned plot. (Photo copyright © by Kaj Halberg)
Obscure morning-glory, climbing on fences. (Photos copyright © by Kaj Halberg)
Crassulaceae Stonecrop family
This family, also called orpine family, includes about 35 genera and 1,400 species. It is found worldwide, with the greatest diversity in the Northern Hemisphere and in southern Africa. It is characterized by plants with succulent leaves – an adaptation to growing in dry areas with little water.
Most stonecrops are creeping plants, which grow in dry areas, such as in sand, among scree, or on rocks. This genus, comprising about 470 species, is mainly distributed in the Northern Hemisphere, but also in southern Africa and in South America.
Sedum acre Biting stonecrop
Biting stonecrop was named due to the bitter, peppery taste of its leaves, caused by their content of slightly toxic alkaloids. It is also known by a number of other common names, including mossy stonecrop, goldmoss stonecrop, and wall pepper. It is native to Europe, Turkey, and northern Africa, and has also become naturalized in other countries, including United States, Japan, and New Zealand.
Biting stonecrop, growing in a crack between granite steps in the town of Rønne, Bornholm, Denmark. (Photo copyright © by Kaj Halberg)
Cucurbitaceae Cucumber family
Luffa acutangula Angled luffa
This plant has many other common names, including ridged gourd and sponge gourd. It is a native of Tropical Asia, where it is also widely cultivated. Young fruits are cooked as a vegetable, or pickled, and the fibres inside mature fruits are used as a sponge or for making hats.
The species is also utilized in traditional folk medicine. The seeds are emetic and purgative, and they are eaten to expel intestinal worms. Fruit and seeds are also used in treatment of venereal diseases, especially gonorrhea.
The pictures below are from the city of Taichung, Taiwan, where angled luffa often escapes cultivation.
In this picture, angled luffa is covering an abandoned plot. (Photo copyright © by Kaj Halberg)
This plant is climbing over abandoned machinery. (Photo copyright © by Kaj Halberg)
This one is climbing along a wire. (Photo copyright © by Kaj Halberg)
From vegetable gardens, these cultivated luffas are climbing up fences. In the lower two pictures, several plants have climbed so high, that they could not be harvested, allowing them to produce mature fruits and spread their seeds. (Photos copyright © by Kaj Halberg)
Momordica charantia Bitter gourd
This plant, also called bitter melon, originated in Africa, where it was a staple food of the Kung hunter-gatherers (‘Bushmen’). At a very early stage, it was brought to Asia, where it is widely used in the various cuisines today.
Bitter gourd, escaped from cultivation along a road, Taichung, Taiwan. Leaves of angled luffa (above) are also seen. (Photo copyright © by Kaj Halberg)
Euphorbiaceae Spurge family
This prostrate plant is a pantropical weed, which is native to Tropical America, but has been introduced, partly as a medicinal plant, partly unintentionally, to most warmer regions of the world. It often grows along roads, in fallow fields, and in abandoned plots. It is sometimes called asthma plant, referring to one of its usages in traditional herbal medicine. It has also been utilized for female disorders, cough, bronchitis, worm infestations in children, dysentery, jaundice, pimples, gonorrhea, digestive problems, and tumors.
Euphorbia hirta, growing in a lawn in a city park, Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
In this picture, Euphorbia hirta has taken root in a crack in an abandoned parking lot, Taichung. (Photo copyright © by Kaj Halberg)
Ricinus communis Castor oil plant
The castor oil plant, which is probably indigenous to the Middle East and north-eastern Africa, has been widely cultivated elsewhere for thousands of years. Today, it is a widespread weed in almost all tropical and subtropical countries.
The generic name is Latin, meaning ‘tick’, referring to the seed, which resembles certain species of ticks. Another common name of this plant is Palm of Christ, which refers to the ability of its oil to heal wounds and cure various ailments.
The medical properties of castor oil plant are described on the page Plants: Plants in folklore and poetry.
The pictures below are from Taiwan, where this species is extremely common in the lowlands, often invading fallow plots in cities.
This castor oil plant, which shows the red female flowers above and the white male flowers below, has taken root in a crack in the concrete wall along a rainwater drainage canal in the city of Taichung. (Photo copyright © by Kaj Halberg)
This specimen, with ripe fruits, grows in an abandoned plot in Taichung. (Photo copyright © by Kaj Halberg)
Geraniaceae Crane’s-bill family
A genus with about 60 species, which are native to Europe, especially areas around the Mediterranean, and thence eastwards through the Middle East to Central Asia, and also to southern North America, and Australia.
In Europe, these plants are known as stork’s-bills, whereas they are called filarees or heron’s bills in North America. These names all refer to the shape of the fruit. The ripe fruit splits into five segments, each with a long, spirally twisting style, with a seed attached at the base. As the style twists, it is able to drill the seed into the soil.
Erodium cicutarium Common stork’s-bill
This plant is native to Europe, North Africa, and parts of Temperate Asia, but has been accidentally introduced to many parts of the world, including North America, Australia, New Zealand, Japan, and Chile. In many places, it is considered a noxious weed, as it is most proliferate, readily outcompeting native plant species and crops.
Common stork’s-bill, growing at a house wall, Jutland, Denmark. (Photo copyright © by Kaj Halberg)
Malvaceae Mallow family
Malva sylvestris Common mallow
This species is native to Temperate Asia, Europe, and North Africa, but has been introduced elsewhere as an ornamental. It has become naturalized in many countries, including Australia, the United States, Canada, and Mexico.
In this picture, common mallow grows on a graveyard wall next to Nylars Church, Bornholm, Denmark. (Photo copyright © by Kaj Halberg)
A widespread genus of about 30 species of prostrate plants, found from Ussuriland, south-eastern Siberia, through China, Korea, Japan, Taiwan, the Indian Subcontinent, and Southeast Asia, southwards to Australia and New Zealand. Initially, they were placed in the family Scrophulariaceae, later in Phrymaceae, and now in the recently established family Mazaceae.
A small Mazus species, possibly M. pumilus, growing i dirt, which has accumulated in a metal drain at the edge of a street, Taichung, Taiwan. Creeping woodsorrel (Oxalis corniculata, see below) is also present. (Photo copyright © by Kaj Halberg)
Meliaceae Mahogany family
Melia azedarach Persian lilac
This large tree, also known as Chinaberry or bead tree, is probably native to Iran and the Indian Subcontinent, but due to its beautiful flowers and fruits it has been widely planted elsewhere. It readily spreads and has become an invasive species in various places, including North America, East Africa, some Pacific Islands, New Zealand, and Australia.
In Taiwan, this species is planted extensively, and escaped specimens may sometimes be encountered.
Flowering Persian lilac beneath a bridge, Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
The name bead tree was given in allusion to the perfectly round fruits, which resemble beads in a rosary. These pictures were taken in Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
Moraceae Fig family
Broussonetia papyrifera Paper mulberry
Paper mulberry is a small tree, native to East and South Asia and possibly to some Pacific islands. It thrives in a wide range of habitats and climates, readily growing in disturbed areas. It is dioecious, and when male and female plants grow together, and seeds are produced, it spreads rapidly. Birds and other animals eat the fruits and thus help dispersing the species. It can also form dense stands via its spreading root system.
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.
In Taiwan, paper mulberry is very common in cities, popping up everywhere, as in these pictures from Taichung.
Numerous specimens of paper mulberry have taken root in cracks in a wall along a drainage canal, together with downy bur-marigold (Bidens pilosa, see above). (Photo copyright © by Kaj Halberg)
The leaf shape of paper mulberry varies from almost entire to deeply indented. (Photos copyright © by Kaj Halberg)
Paper mulberry, growing near a playground. (Photo copyright © by Kaj Halberg)
Males inflorescences. (Photo copyright © by Kaj Halberg)
The orange fruits are edible. (Photo copyright © by Kaj Halberg)
Ficus superba Large-leaved fig tree
This large tree, which is distributed in China, Taiwan, Japan, and parts of Southeast Asia, southwards to Indonesia, belongs to a group of fig trees, called strangler figs.
Most seeds of these trees begin their life as an epiphyte in a tree, the seed often sprouting in a pile of bird dung, delivered by the bird which ate the fig fruit. Over the years, aerial roots of the young strangler fig grow down to the ground, where they take root, whereas other roots wrap themselves around the host tree, over time completely enveloping the tree, which is eventually strangled to death. As the trunk of the host tree decays, it leaves the fig tree as a hollow cylinder of aerial roots. It readily grows on buildings, too, and is also able to thrive as a normal free-standing tree.
Other fig trees are presented on the page Plants: Ancient and huge trees.
Aerial roots of a giant large-leaved fig, climbing over the remains of a former warehouse of Tait & Co., in the town of Anping, Taiwan. Today, the building is called Anping Tree House. (Photos copyright © by Kaj Halberg)
Morus australis Japanese mulberry
This small tree, also known as Korean mulberry or Chinese mulberry, grows to about 10 m tall. It is native to Japan, Korea, southern China, and Taiwan, growing along forest margins, on mountain slopes, and in shrubberies and fallow lands, from the lowlands up to an elevation of about 2,000 m.
The fruits, which resemble bramble berries, are edible raw, and a fine jam can be made from them. Caterpillars of the butterfly Calinaga buddha (Nymphalidae) feed on leaves of this tree.
In Taiwan, Japanese mulberry has readily adapted to a life in cities, popping up in cracks everywhere.
Fruiting Japanese mulberry, Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
Onagraceae Evening-primrose family
This is a genus of c. 82 species of mainly aquatic plants, found mostly in the Tropics. 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?
Ludwigia hyssopifolia Narrow-leaved primrose-willowherb
The origin of this plant, which grows to 2 m (sometimes 3 m) high, is not clear. Today, it is a very widespread weed of rice fields and wetlands in tropical and subtropical areas around the world. The upper stem is ribbed, and the leaves are lanceolate, to 10 cm long and 1-2 cm wide, with a short stalk.
The specific name refers to the likeness of its leaves to those of hyssop (Hyssopus officinalis), of the mint family (Lamiaceae).
The pictures below are all from the city of Taichung, Taiwan.
Narrow-leaved primrose-willowherb, growing at the edge of a field at the outskirts of Taichung. (Photo copyright © by Kaj Halberg)
This one has sprouted in the dried-out bed of the Fazi River. (Photo copyright © by Kaj Halberg)
The flowers of narrow-leaved primrose-willowherb are quite small, with 4 petals. (Photo copyright © by Kaj Halberg)
Withering leaves of narrow-leaved primrose-willowherb turn a pretty yellowish-reddish. Note the grooved stem, a characteristic of this species. (Photo copyright © by Kaj Halberg)
Ludwigia octovalvis Mexican primrose-willowherb
Despite its name, the native area of this species is unknown, and today it is found in most tropical and subtropical areas of the world. It easily becomes naturalized and is regarded as an invasive in some countries. The stem is downy, without grooves, and the leaves are quite variable, elliptic, ovate, linear, or lanceolate. The flowers usually have 4 large yellow petals, sometimes 5.
This species closely resembles water primrose-willowherb (L. peploides), which, however, usually has elliptic or ovate leaves and 5 overlapping petals.
The pictures below are all from Taiwan, where Mexican primrose-willowherb is common in wet habitats, especially along streams.
Mexican primrose-willowherb, forming a huge growth along a river near Linbei Chukou, Linnei. (Photo copyright © by Kaj Halberg)
In this picture, it grows in the dried-out bed of the Fazi River, Taichung. (Photo copyright © by Kaj Halberg)
This growth was encountered in drainage canal in Taichung. (Photo copyright © by Kaj Halberg)
Flowers of Mexican primrose-willowherb usually has 4 petals. – Taichung. (Photo copyright © by Kaj Halberg)
This large genus, comprising about 145 species, is native to the Americas, but many species are widely cultivated for their attractive flowers, which unfold late in the evening, stay open at night, and wither during the following day. This is an adaptation to being pollinated by insects that are active during the night, including moths.
These plants vary greatly in size, from dwarves 10 cm high to giants 3 m tall. Most species have yellow flowers, some white, purple, pink, or red. Despite their name, they are not closely related to the true primroses (Primula).
Oenothera glazioviana Large-flowered evening-primrose
This impressive plant, previously known as O. erythrosepala, may grow to 2 m tall. It is a native of Brazil, but is widely cultivated as an ornamental plant, often becoming naturalized.
Large-flowered evening-primrose, growing in an abandoned plot in the town of Nyborg, Denmark. The grass is red fescue (Festuca rubra). (Photo copyright © by Kaj Halberg)
Oxalidaceae Woodsorrel family
Oxalis corniculata Creeping woodsorrel
This species has a creeping stem, rooting at the nodes. The leaves are trifoliate, resembling clover leaves (Trifolium). The leaves are edible, with a taste reminiscent of lemons.
The native area of the plant is possibly Southeast Asia, but today it has an almost cosmopolitan distribution, and is often regarded as a noxious weed in gardens, fields, and lawns. It may have been introduced to Italy before 1500. It was described scientifically in 1753 by Swedish naturalist Carl Linnaeus (1707-1778), who received specimens from Italy. (Source: Q.J. Groom, J. van der Straeten & I. Hoste 2019. The origin of Oxalis corniculata L. PubMed 30783568)
Creeping wood-sorrel, growing in a gutter, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Papaveraceae Poppy family
Papaver dubium Long-headed poppy
Long-headed poppy is very common in the major part of Europe, in North Africa, and in western Asia, eastwards to the Himalaya. It mostly grows along roads and in fallow fields.
A number of pictures, depicting this species and many other poppies, may be seen on the pages In praise of the colour red, and In praise of the colour yellow.
These long-headed poppies have taken root in a crack along a house wall, Bornholm, Denmark. (Photo copyright © by Kaj Halberg)
Pseudofumaria lutea Yellow corydalis
This species, previously known as Corydalis lutea, is native to the south-western and central Alps of Italy and Switzerland. However, it has been widely introduced in many countries as an ornate garden plant. It is extremely lush and often escapes, popping up in cracks along house walls, and elsewhere.
A lush growth of yellow corydalis along a house wall, Funen, Denmark. (Photo copyright © by Kaj Halberg)
Plantaginaceae Plantain family
Cymbalaria muralis Ivy-leaved toadflax
Due to its pretty flowers and vigorous growth, this species, which is a native to the Mediterranean, has been introduced to many parts of the world as an ornamental. In some areas, however, it has escaped cultivation and has become an invasive. The common name refers to the leaves, which resemble those of ivy (Hedera helix).
Ivy-leaved toadflax, growing on a stone wall, Bornholm, Denmark. The plant in the lower right corner is greater celandine (Chelidonium majus). This species is described on the page Plants: Plants in folklore and poetry. (Photo copyright © by Kaj Halberg)
This ivy-leaved toadflax is growing on the wall of Winchester Cathedral, southern England. (Photo copyright © by Kaj Halberg)
Plantago major Greater plantain
This plant is native to Europe and Temperate Asia, but has been introduced to many parts of the world, often becoming naturalized. When the Europeans emigrated to North America, the sticky seeds of this species often stuck to wagon wheels and were spread, wherever the immigrants went. This was noticed by the indigenous peoples, who called it ‘white man’s footprint’.
Greater plantain, growing in a crack along a gutter, Jutland, Denmark. The red object is a rose petal. (Photo copyright © by Kaj Halberg)
Plumbaginaceae Sea-lavender family
Armeria maritima Thrift
The generic name of this plant is probably of Celtic stock, from ar (’near’) and mor (’sea’). In his Commentarii de Bello Gallico (‘Notes on the Gallic War’), Roman emperor Gaius Julius Caesar (100-44 B.C.) mentions an area between the rivers Seine and Loire, which he calls Aremorica. Presumably, thrift was growing here.
The Old French name of the plant, armoires, became Latinized as armerios in 1537, later as Armeria. (Source: Corneliuson, J. 1997. Växternas namn. Vetenskapliga växtnamns etymologi. Språkligt ursprung och kulturell bakgrund. (‘Etymology of plant names’, in Swedish)
The specific name, from the Latin mare (’sea’), informs us that thrift is a seashore plant. However, following the introduction of salt-strewing on snow-covered roads in northern Europe, this species has spread inland, where it is now common along roads, even in cities.
In the old days, when sweets were not everyday treats like today, children would suck out nectar from flowers of thrift – or simply eat the entire inflorescence.
Thrift, growing in a crack in a sidewalk, Jutland, Denmark. (Photo copyright © by Kaj Halberg)
Poaceae Grass family
This grass has found its way through an opening in a discarded car, where the rear light glass is missing, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Bromus sterilis Barren brome
This grass, also called poverty brome or sterile brome, is very common species, native to the major part of Europe, North Africa, and Asia, eastwards to Turkmenistan and Uzbekistan. It grows in a wide variety of open habitats, including waste areas, roadsides, and gardens.
Barren brome often grows in cities, here photographed next to a red house wall in the town of Svaneke, Bornholm, Denmark. (Photo copyright © by Kaj Halberg)
Cenchrus echinatus Southern sandspur
If you have once stepped barefoot on the spiny fruits of this grass, you will never forget it. The specific name is derived from the Greek ekhinos (‘hedgehog’), alluding to the fruits, which have lots of sharp spines. This fact is also reflected by its common names, which include spiny sandbur, burgrass, and hedgehog grass.
This species is native to tropical America, but has become naturalized in most tropical and subtropical areas, easily spreading by its spiny fruits, which attach themselves to almost anything. It grows in many different habitats and is regarded as an agricultural weed in 35 countries.
Flowering southern sandspur, encountered in a city park, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Here, southern sandspur is growing next to a busy road in Taichung. The tall plant to the left is horsetail fleabane (Erigeron canadensis, see above). (Photo copyright © by Kaj Halberg)
These pictures from Taichung show the spiny fruits of southern sandspur. (Photos copyright © by Kaj Halberg)
Chloris barbata Peacock-plume grass
The origin of this plant, which is also known by the names purple top and swollen fingergrass, is uncertain. Some authorities maintain that it is native to Tropical America, others claim that it is indigenous in Tropical Africa.
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 pictures below are all from Taiwan, where peacock-plume grass is extremely common, often covering large tracts of fallow land.
Huge growth of peacock-plume grass in a fallow plot, Ziguan, north of Kaohsiung. (Photo copyright © by Kaj Halberg)
Spikes, moving in the wind, Taichung. (Photos copyright © by Kaj Halberg)
These tufts of peacock-plume grass have taken root in cracks in the asphalt in an abandoned parking lot, Taichung. (Photos copyright © by Kaj Halberg)
Here, it grows along a house wall, Taichung. (Photo copyright © by Kaj Halberg)
In this picture, a tuft is growing up a wall along a rainwater canal, Taichung. The wind has moved the inflorescences back and forth, scraping dirt off the wall in semi-circles. (Photo copyright © by Kaj Halberg)
Close-up of spikes, Taichung. (Photo copyright © by Kaj Halberg)
Withered peacock-plume grass can also be very decorative. – Taichung. (Photo copyright © by Kaj Halberg)
Festuca rubra Red fescue
Red fescue is a very adaptable species, which can grow in most open habitats, including beaches and dunes. This grass is widespread across much of the Northern Hemisphere, mainly in temperate areas. It has also adapted to a life in cities.
Red fescue, growing along a water front at Lake Mälaren, central Stockholm, Sweden. (Photo copyright © by Kaj Halberg)
Hordeum murinum Wall barley
Wall barley, also called false barley, is native to Europe, North Africa, and western Asia. It has readily adapted to a life in cities.
These pale spikes of wall barley stand out against house walls in the village of Jyllinge, Zealand (top), and in the town of Rønne, Bornholm, both in Denmark. (Photos copyright © by Kaj Halberg)
Melinis repens Natal grass
As its name implies, this species is native to South Africa. However, it has been introduced as an ornamental, or unintentionally, to many other parts of the world. At maturity, its inflorescence is coated in white, silky hairs.
Natal grass is very common in Taiwan, often growing along roads or in abandoned plots. The pictures below are all from Taichung.
Flowering inflorescences of Natal grass are of a gorgeous reddish colour. These plants had sprouted in cracks in an abandoned parking lot. (Photos copyright © by Kaj Halberg)
White seed-heads of Natal grass, glowing against the light. These plants were growing at the edge of a walkway along the Han River. (Photo copyright © by Kaj Halberg)
Panicum repens Torpedograss
The native area of this species, also known as creeping panicum or bullet grass, is unknown, but today it is found throughout the world in tropical and subtropical areas. 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.”
Torpedograss is very common in Taiwan, also in cities. These pictures are all from Taichung.
In these pictures, torpedograss forms a large growth along a fence. (Photos copyright © by Kaj Halberg)
Torpedograss, growing next to a wall. (Photo copyright © by Kaj Halberg)
Close-up of inflorescences. (Photo copyright © by Kaj Halberg)
Torpedograss is also decorative after dispersing its seeds. (Photo copyright © by Kaj Halberg)
Pennisetum Fountain grasses
This genus, comprising 80-140 species, is native to warmer parts of Africa, Asia, Australia, and Latin America, and some species are widely naturalized in Europe and North America. The spikes are densely bristled, and in some species the bristles are coated in plume-like hairs, which gave rise to the generic name, from the Latin penna (‘feather’) and seta (‘bristle’).
Pennisetum alupecuroides Foxtail fountain grass
This species, also called Chinese fountain grass or dwarf fountain grass, is native from eastern Asia southwards to Australia. The specific name stems from the Latin Alopex, a genus of foxes now transferred to the genus Vulpes, and oides (‘resembling’), thus ‘like a fox tail’, alluding to the long spikes.
Foxtail fountain grass is very common in Taiwan, also in cities. This picture is from Taichung. (Photo copyright © by Kaj Halberg)
Foxtail fountain grass, photographed in rainy weather on a hill near Nanfangao, a huge fishing harbour south of Yilan, Taiwan. (Photo copyright © by Kaj Halberg)
Polygonaceae Buckwheat family
Polygonum aviculare Common knotgrass
This prostrate herb is very common, growing on sandy beaches, in fields and wasteland, and in towns. It is widespread in temperate regions of the Northern Hemisphere, probably native to Eurasia as well as North America. It has also become naturalized in temperate areas of the Southern Hemisphere.
Common knotgrass, growing among bricks, laid out as tiles, Jutland, Denmark. (Photos copyright © by Kaj Halberg)
Rumex Docks and sorrels
This huge, almost worldwide genus has about 200 members. Dock is an old term applied to various plants with large leaves, whereas sorrel is a brownish-orange to pale chestnut colour, referring to the brown fruits of this genus.
Rumex japonicus Japanese dock
This is a widespread species in the Far East, growing along fields and streams, and in humid valleys, from sea level to 3,400 m altitude. It is distributed from south-eastern Siberia, Mongolia, and northern China southwards through Korea and Japan to Taiwan and southern China. It is utilized in traditional medicine.
Leaves of a Japanese dock, which has sprouted in a wall along a drainage canal, Taichung, Taiwan. The pink blots are eggs of the golden apple snail (Pomacea canaliculata), described on the page Nature: Invasive species. (Photo copyright © by Kaj Halberg)
The picture below shows vegetation at a sewage outlet in Taichung. The plant with large leaves is Japanese dock, whereas the one with white flowers is downy bur-marigold (Bidens pilosa, see above), and the one with yellow flowers is Mexican primrose-willowherb (Ludwigia octovalvis, see above).
(Photo copyright © by Kaj Halberg)
Polypodiaceae Polypody family
A member of the polypody family, growing out of a drainage pipe, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Ranunculaceae Buttercup family
Clematis vitalba Traveller’s joy
A most vigorous climber, occasionally reaching a length of more than 20 m, with thick, woody stems to 6 cm in diameter. Leaves opposite, pinnate, with 5 (rarely 3) widely spaced leaflets, thin, sparsely hairy, entire or toothed. Flowers are arranged in umbel-like clusters, creamy-white, fragrant, to 3 cm across.
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.
In this picture, traveller’s joy is climbing along a fence on a bridge, Nyborg, Funen, Denmark. (Photo copyright © by Kaj Halberg)
Rubiaceae Bedstraw family
This large genus of shrubs, small trees, or climbers, comprising at least 180 species, is native to tropical and subtropical areas of Asia and Africa.
Mussaenda parviflora Small-flowered mussaenda
This small, climbing shrub is native to Japan, southern China, and Taiwan. Its natural habitats are forests and shrubberies, up to an elevation of about 1,700 m, but it has readily adapted to a life in urban environments.
Small-flowered mussaenda is quite common in the lowlands of Taiwan. This specimen has taken root near a house wall in Taichung. (Photo copyright © by Kaj Halberg)
Paederia scandens Chinese fever vine
A climber, distributed from north-eastern India eastwards to Japan, Korea, China, Taiwan, and Southeast Asia, growing in shrubberies and open areas from the lowlands to elevations of about 800 m.
The whole plant emits a foetid aroma when rubbed, giving rise to a number of popular names, including chicken dung vine, stinky vine, and dog fart vine. It is widely utilized in folk medicine for a number of ailments, including fever, aches, jaundice, dysentery, and dyspepsia.
Chinese fever vine is very common in Taiwan, also in cities. These pictures are from Kenting (top) and Taichung. (Photos copyright © by Kaj Halberg)
Sapindaceae Soapberry family
Cardiospermum halicacabum Balloon vine
Balloon vine is a climbing herb, which is easily recognized by its swollen fruits. The tiny seeds are black with a white spot, shaped like a heart, hence its generic name, from the Greek kardia (‘heart’) and sperma (‘seed’), as well as the common names heart pea and love-in-a-puff (the seeds are hidden inside the swollen fruits).
This species is widely distributed in tropical and subtropical Africa and Asia, and has also become naturalized in many other parts of the world. 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.
Balloon vine is ubiquitous in Taiwan, climbing on other plants or on fences. The pictures below are all from the city of Taichung.
Balloon vine, climbing up fences. (Photos copyright © by Kaj Halberg)
This plant has sprouted among stones in the dried-out bed of the Fazi River. (Photo copyright © by Kaj Halberg)
This one is clinging to barbwire. (Photo copyright © by Kaj Halberg)
Solanaceae Nightshade family
This genus of about 67 species of shrubs or shrubby herbs are commonly referred to as tobacco plants. Most species are indigenous to the Americas, with some found in the South Pacific, Australia, and south-western Africa. The true tobacco plant (N. tabacum) is widely grown for production of tobacco, whereas others are cultivated as ornamentals.
Anchored off the coast of what is today called Cuba, in November 1492, Cristoforo Colombo (1451-1506), in English known as Christopher Columbus, wrote in his journal, that his messengers had seen natives carrying “some sort of cylinder, in which sweetly smelling herbs were glowing. These, they supposed, were dried herb stalks, covered by an equally dry but broader leaf. The people sucked the opposite end of the cylinder and, as it were, drank the smoke. Although this apparently intoxicated them, it also seemed to protect them from fatigue. The natives called these cylinders tabacos.”
Nicotiana plumbaginifolia Mexican tobacco
This plant, popularly called Tex-Mex tobacco, is native to the Caribbean, Mexico, and Central and South America. It has been introduced, intentionally or accidentally, to many countries in Asia, and also to southern United States. It mainly grows in cultivated fields and wastelands, and is often considered an unwanted weed.
The specific name refers to the leaves, which resemble those of some species in the genus Plumbago.
In recent years, Mexican tobacco has been accidentally introduced to Taiwan. In these pictures, it grows along a wooden fence in Taichung. (Photos copyright © by Kaj Halberg)
One of the largest plant genera in the world, counting more than 1,300 species, among which is a number of cultivated plants, including potato (S. tuberosum), tomato (S. lycopersicum), tomato tree (S. betaceum), and eggplant (S. melongena).
This genus is dealt with in detail on the page Plants: Plants in folklore and poetry.
Solanum erianthum Potato tree
A native of North and Central America, potato tree has been introduced to numerous other countries, and in many areas it is regarded as an “environmental weed”.
Potato tree is very common in Taiwanese cities, often growing in vacant lots, and in cracks along walls and canals. This specimen was photographed in an abandoned lot in Taichung. (Photo copyright © by Kaj Halberg)
Fruiting potato tree, Taichung. (Photo copyright © by Kaj Halberg)
Solanum indicum Indian nightshade
This shrubby herb, also known as S. violaceum, grows to about 3 m tall. It resembles potato tree, but its leaves are lobed and wavy, and it has prickles on the stems and sometimes also along the leaf nerves. The smallish berries, to 2 cm across, are either orange or yellow. This plant is is native to the Indian Subcontinent and Southeast Asia, but has become naturalized in numerous countries in warmer areas.
Indian nightshade is very common in the lowlands of Taiwan, here photographed in the city of Taichung. (Photos copyright © by Kaj Halberg)
Solanum nigrum Black nightshade
This species probably originates in southern Europe, but has become naturalized in most parts of the globe. In northern Europe, it is a common weed in vegetable gardens, reflected in the common names garden nightshade and garden huckleberry. Other names include hound’s berry and wonder berry.
Black nightshade, growing at a house wall, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)
Xanthoria parietina Common orange lichen
This species, also called yellow scale or shore lichen, is a leafy lichen with a very wide distribution, found in most of Europe, Africa, Asia, Australia, and North America. It is one of the few lichens, which is favoured by eutrophication, being very common on rocks, large trees, roofs, walls, etc.
Tombstone with growth of common orange lichen, Kirke Stillinge, Zealand, Denmark. (Photo copyright © by Kaj Halberg)
Old wall in the town of Enkhuizen, West-Friesland, Holland, with vegetation of common orange lichen and wall-rue (Asplenium ruta-muraria), a fern. (Photo copyright © by Kaj Halberg)
Common orange lichen, growing on a heraldic lion, Nyborg, Denmark. (Photo copyright © by Kaj Halberg)
Urticaceae Nettle family
Parietaria judaica Spreading pellitory-of-the-wall
This plant often grows on buildings and stone walls in cities, and along roads. It is native to southern Europe, central and western Asia and northern Africa, but has been widely introduced to many other places. In Australia, California, and elsewhere, it is considered an invasive weed.
Spreading pellitory-of-the-wall, growing on a house wall, Sultanahmet, Istanbul, Turkey. Another picture is shown on top of this page. (Photo copyright © by Kaj Halberg)
Vitaceae Grape family
Ampelopsis glandulosa Porcelain berry
This climber is distributed in eastern Asia, from south-eastern Siberia southwards through China, Japan, and Taiwan to India, Nepal, Southeast Asia, and the Philippines.
It is widely cultivated elsewhere and has become naturalized in numerous places, including in the eastern United States, where it is regarded as highly invasive, establishing itself along streams and ponds, at forest edges, and in other disturbed areas. The colourful berries are eaten by birds and small mammals, dispersing the seeds in their droppings.
Porcelain berry, var. brevipedunculata, climbing over rusted machinery, Taichung, Taiwan. (Photos copyright © by Kaj Halberg)
(Uploaded September 2020)
(Latest update March 2022)