Fruits of great burdock (Arctium lappa) with spiders’ webs and dew drops, photographed on a dark October morning, Nature Reserve Vorsø, Horsens Fjord, Denmark. (Photo copyright © by Kaj Halberg)



Fruiting downy bur-marigold (Bidens pilosa), Mulkharka, Shivapuri National Park, central Nepal. (Photo copyright © by Kaj Halberg)



Southern sandspur (Cenchrus echinatus), growing next to a busy road in Taichung, Taiwan. The tall plant to the left is horsetail fleabane (Erigeron canadensis). (Photo copyright © by Kaj Halberg)




Botanically, a bur is any fruit with a rough or prickly surface, often armed with hooks. When the seeds are ripe, the hooks readily attach themselves to an animal’s pelt or a person’s socks or trousers, if they happen to bruise the plant. In this way, the fruits may be spread a considerable distance from the mother plant.

The term is derived from Middle English burre, adapted from the Norse burre, the name of burdock (below).


Arctium Burdock
This genus of stout, biennial plants, comprising about 15 species, is native to Europe and northern Asia, but several species have been widely introduced elsewhere.

The stem is divided into several branches, and at the end of these are many flowerheads with lovely, reddish-violet flowers, which attract numerous hoverflies, bumblebees, and butterflies. Each of the flowerheads is surrounded by an armour of hooked spines. When the seeds are ripe, the entire flowerhead is easily detached, for instance when the pelt of a fox or a woollen sweater brushes against the hooks.

Even when the plant is flowering, these hooks are nasty, and woe the small bird or bat whose wing gets stuck on the hooks. They will face a slow death, unless a predator passes by.

In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes about the burs: “Sometimes (a boy) is mean enough to throw a bunch of the burs into the hair of a rival, or even into the hair of the girl he thinks has snubbed him. She who has had this experience needs no technical description of the burdock.”

The generic name is derived from the Greek arktos (‘bear’), in allusion to the burs, which are somewhat similar to bear claws. Of course, the name burdock also refers to the burs, dock being a term applied to various plants with large leaves. And burdock leaves are large, growing up to 70 cm long and almost as wide.


Great burdock (Arctium lappa)
This plant, which grows in disturbed areas, is native to Eurasian temperate regions, found from Scandinavia southwards to the Mediterranean, and from the British Isles across Siberia and the Middle East to northern India, China, Taiwan, and Japan. Elsewhere, it has become naturalized, and it is considered an invasive weed in North America and Australia.

One authority states that the specific name stems from the Celtic word llap (‘hand’), alluding to the ‘gripping’ burs. The popular name herrif is derived from two Anglo-Saxon words, haeg (‘hedge’), and reafe (‘robber’), perhaps referring to the vigorous growth of this species. Other folk names include fox’s clote, thorny bur, clot-bur, beggar’s buttons, and cockle buttons.

The role of great burdock in folklore, poetry, and medicine is described on the page Plants: Plants in folklore and poetry.



When left alone, great burdock can grow to an impressive size. This one was photographed in Nature Reserve Vorsø, Horsens Fjord, Denmark. (Photo copyright © by Kaj Halberg)



Great burdock has beautiful, reddish-violet flowers, which are much visited by butterflies. A small tortoiseshell (Aglais urticae) is seen in the upper picture. – Nature Reserve Vorsø. (Photos copyright © by Kaj Halberg)



Along the edge of the burdock flowerheads are numerous hooked prickles. One wing of this blue tit (Cyanistes caeruleus) got stuck in these hooks, causing the death of the bird. – Vorsø. (Photos copyright © by Kaj Halberg)



Here, a wing of a common pipistrelle (Pipistrellus sp.) has been caught in the hooks. – Vorsø. (Photo copyright © by Kaj Halberg)



Seed heads of great burdock, weighed down by snow, Vorsø. (Photo copyright © by Kaj Halberg)




Bidens Bur-marigold
This huge genus of herbs, comprising between 150 and 250 species, is mainly native to warmer areas of the Americas. However, a large number of species have been accidentally introduced to many other warmer parts of the world.

The generic name is from the Latin bi (’two’) and dens (’tooth’), alluding to the mostly 2 (sometimes 3 or 4) sharp, hooked teeth on the seeds, which easily get attached to animals’ pelts or people’s clothes, hereby often being spread a considerable distance from the mother plant. This way of seed dispersal has given rise to names like beggar-ticks, stickseed, farmer’s friend (sic!), needle grass, Spanish needles, stick-tight, cobbler’s pegs, Devil’s needles, and Devil’s pitchfork.

In the 1700s, sheep were fed with bur-marigold to protect them from disease and intestinal worms.


Trifid bur-marigold (Bidens tripartita)
This is a common and widespread species, native to almost the entire Eurasia, southwards to North Africa, Pakistan, and northern Indochina. It is also widespread in North America, and it may also be indigenous to the Philippines. Naturalized populations occur in Australia and on some Pacific Islands. It is partial to wetlands and can grow in rather polluted water.

It was formerly used as a remedy for bleeding, kidney problems, and ulcers. Young leaves are edible when cooked.

The specific name refers to the tripartite leaves.



Trifid bur-marigold, Lake Brabrand, eastern Jutland, Denmark. (Photo copyright © by Kaj Halberg)




Nodding bur-marigold (Bidens cernua)
Like the previous species, this plant is partial to wetlands. It has a more or less similar distribution, but is not nearly as common. It is much larger, growing to about 1 m tall, and its nodding flowerheads are much bigger, with prominent yellow ray florets.

The specific name is Latin, meaning ‘nodding’.



Nodding bur-marigold, Lake Filsø, western Jutland, Denmark. (Photo copyright © by Kaj Halberg)




Downy bur-marigold (Bidens pilosa)
This plant is a pan-tropical and -subtropical weed of unknown origin, which has become a pest in many 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 way 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.”

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.

The specific name is Latin, meaning ‘hairy’.



Downy bur-marigold is highly invasive in Taiwan, often covering huge areas. In this picture, several plants have sprouted in a crack in a dried-out canal, Taichung. (Photo copyright © by Kaj Halberg)



The hooked seeds of downy bur-marigold readily spread by sticking to animals’ furs, socks, trousers, etc. These pictures are from Taichung. (Photos copyright © by Kaj Halberg)



In this picture, one of the hooks on a seed of downy bur-marigold has become attached to a wing of this moth, causing the death of the animal. – Marsyangdi Valley, Annapurna, central Nepal. (Photo copyright © by Kaj Halberg)




Cenchrus Sandspur, sandbur
A large genus with about 107 species, distributed in warmer areas around the globe. The generic name is Latin, derived from Ancient Greek kenkhros (‘millet’). The common names allude to the very sharp spines on the fruit.

In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes about an American species, C. tribuloides: “Most people know only the bur (of this species), which is one of the sharpest of armed fruits. It sticks to the clothing and pierces the fingers when one attempts to remove it. No other grassy plant has this fruit, this lance-armed bur, and a description therefore is almost useless. He who finds a sandbur does not have to be told what it is.”


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)



This picture from Taichung shows the spiny fruits. (Photo copyright © by Kaj Halberg)




Circaea Enchanter’s nightshade
A small genus with 8 species of herbs, native to temperate and boreal forests of the Northern Hemisphere.

The generic name refers to Circe, in Ancient Greek Kirke, a mythical sorceress, who had a vast knowledge of magic potions and herbs. Using these, and a magic wand, she was able to transform her enemies to beasts. Efter poisoning her husband, she settled on the island of Aiaia. When Odysseus landed on her island on his way back from Troy, she transformed his men into swine, but, with the help of the god Hermes, he forced her to end the spell.

The name of the sorceress is derived from the verb kirkoô (‘to secure with rings’), alluding to the binding power of magic. Supposedly, she used plants of this genus in her spells, reflected in the English name. These plants are not especially toxic, but contain much tannin, which is astringent.


Broad-leaved enchanter’s nightshade (Circaea lutetiana)
This plant is found in forests and other shaded places, from England and Portugal eastwards to Kazakhstan, and from Scandinavia southwards to northern Africa, Iraq, and Iran.

The stem grows to 60 cm tall, rarely to 75 cm. The leaves are heart-shaped, long-pointed, toothed, with indented nerves. The white flowers have 2 petals, 2 stamens, and a white or pinkish stigma. The fruit is a small ovoid bur, 3-5 mm long.

The specific name is derived from Lutetia, the Latin name for Paris, which, in the old days, was sometimes referred to as the Witch City.



Broad-leaved enchanter’s nightshade, flowers above, fruits below, Nature Reserve Vorsø, Horsens Fjord, Denmark. (Photo copyright © by Kaj Halberg)




Galium Bedstraw
This huge genus, comprising about 630 species, is native to almost the entire globe.

The generic name is derived from the Greek gala (’milk’), alluding to the usage of yellow bedstraw (G. verum) in rennet, as its flowers are able to coagulate milk to make cheese. In his book Herbal Simples, Dr. William T. Fernie (1830-1914) writes: “The people in Cheshire, especially about Nantwich, where the best cheese is made, do use it [yellow bedstraw] in their rennet, esteeming greatly of that cheese above other made without it.”


Cleavers (Galium aparine)
The specific name of this scrambling plant is derived from the Greek apairo (‘to seize’) – a most descriptive name for this species. Not only the seeds are armed with hooks, but also stems and leaves, which aid the plant in climbing or scrambling over other plants.

In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) has the following comment about this plant: “When one walks into some loose, trailing weeds, and they all seem glad to be torn from their roots in order to ride away clinging to his trousers, he has made contact with (…) either Galium aparine or Galium asprillum. These are the two (species of bedstraw) with the rough stems – the two that have this unique way of scattering their seeds. For of course those straws cling to the sheep’s wool and the dog’s hair just as they do to clothing, and sometimes they and their seeds are carried a long way by animals.”

The common name derives from ‘to cleave’, meaning ‘to stick to’, of course alluding to the stems and seeds sticking to passing animals or persons. It is also known by other names with the same meaning, including catchweed, sticky bob, and sticky willy, whereas robin-run-the-hedge refers to its scrambling habit.

It is native to the major part of Europe, North Africa, and temperate areas of Asia, eastwards to Japan. It may also be indigenous in North America, and it has also become naturalized in Mexico, Central America, South America, Australia, New Zealand, and parts of Africa.



This picture shows the hooks on the stems and the tiny fruits, Djursland, Denmark. (Photo copyright © by Kaj Halberg)



In autumn, cleavers only exists as withered stems with small, ball-shaped fruits. This specimen was once climbing on a wire around a field in eastern Funen, Denmark. (Photo copyright © by Kaj Halberg)




Geum Avens
A genus of about 50 species, widespread in Eurasia, Africa, New Zealand, and the Americas. Most species have yellow flowers, some red, orange, or white. A gorgeous species with orange flowers is shown on the page Travel episodes – Chile 2011: The white forest.

At maturity, the fruits of some species are hooked at the apex, an adaptation to seed dispersal. In other species, a silky tuft of brownish hairs grows from the styles, which has given rise to a popular German name of these plants, Petersbart (‘Peter’s beard’), probably referring to St. Peter.

The generic name is derived from Ancient Greek geno (‘yielding a pleasant aroma’), referring to the clove-like smell of the root, when it has just been dug up. The English name is derived from the Latin avencia, supposedly alluding to of a kind of clover. However, with reference to the generic name, it seems more reasonable to connect it with cloves instead of clover, so maybe someone made a mistake in explaining the name!


Common avens (Geum urbanum)
This is one of the members of the genus with hooked fruits. It is common in most of Europe, eastwards to the Ural Mountains, but is absent from the northernmost regions, and from many Mediterranean islands. It also occurs in north-western Africa, and from Turkey, Syria, and Jordan eastwards to Kazakhstan and Kyrgyzstan.

The specific name is Latin, meaning ‘living in cities’ – a strange name for this plant, which mainly grows in forests, although it may occasionally be found as a weed in city gardens.



Common avens, flower and unripe fruits, Nature Reserve Vorsø, Horsens Fjord, Denmark. (Photo copyright © by Kaj Halberg)




Harpagophytum Devil’s claw
A small genus with 2 species, found in grassy areas and semi-desert in southern Africa. The fruits are very distinctive capsules, woody at maturity, with 2 central spines and 12-16 protrusions, each with 2-3 hooked spines at the apex.

These plants are very important in traditional medicine, and extracts from the tubers are taken for pain and as an anti-inflammatory. They are protected, and collecting may only take place with a permit from the departments of nature conservation.

The generic name is derived from Ancient Greek harpage (‘hook’) and phyton (‘plant’), alluding to the hooks on the fruit, which will stick to an animal or person treading on it. The nastiness of these hooks is reflected in the common name.


Harpagophytum procumbens
This species is distributed in Namibia, Botswana, and South Africa. It is a prostrate, creeping plant with a stout rootstock, which has several storage tubers arising from it. The greyish-green leaves have 3-5 lobes. The trumpet-shaped flowers may be purplish, dark red, or pink, always with a yellow throat.

The specific name is Latin, meaning ‘prostrate’, alluding to the creeping habit of this plant.



Flower and fruit of Harpagophytum procumbens, Palapye, Botswana. (Photos copyright © by Kaj Halberg)




Liquidambar Sweetgum
This genus contains about 15 species of trees, found in eastern North America, Mexico, Central America, Turkey, East and Southeast Asia, and western Indonesia. The fruits are globular and hard, to 5 cm across, with a spiky surface, consisting of the persistent styles.

The generic name is derived from the Latin liquidus (‘liquid’) and the Arabic anbar, which, via the Moors, became ambar in Spanish. Amber from members of this genus was formerly used in the cosmetic industry.

Formerly, these trees were placed in the witch-hazel family (Hamamelidaceae), but have since been transferred to the family Altingiaceae.


Chinese sweetgum (Liquidambar formosana)
This large tree, growing to 40 m tall, is easily identified by its three-lobed leaves, which are almost entire, unlike the usually five-lobed leaves of most Asian maple species (Acer), which are strongly toothed.

It is mainly found in warmer temperate climates, growing in forests as well as in open areas. It is native to central and southern China, Taiwan, and Indochina, but is commonly planted elsewhere as an ornamental tree.

Chinese sweetgum is often used in traditional medicine, the bark for skin diseases, the resin for boils, toothache and tuberculosis, and the fruits for a number of ailments, including arthritis, lumbago, and skin diseases. It seems that leaves and roots can inhibit growth of cancer.

The specific name is from the Portuguese formosa (‘beautiful’), a word that they applied to Taiwan, when they occupied the island. Most species, which bear variants of this name, were described from material stemming from Taiwan.



Pretty winter foliage and globular, prickly fruits of Chinese sweetgum, Hu-tou Shan (‘Tiger Head Hill’), Tungxiao, western Taiwan. (Photo copyright © by Kaj Halberg)



This picture shows fruits of Chinese sweetgum on naked winter branches, Taichung, Taiwan. (Photo copyright © by Kaj Halberg)




Tribulus Caltrop
A genus with about 30 species of prostrate herbs, found in warmer parts of Eurasia, Africa, and Australia.

Fruits of these plants have 2-4 very strong spines, which have given rise to the generic name, from the Greek tribolos, meaning caltrop, a small metal object with several spikes, of which one is always pointing upwards. In the old days, these weapons were spread on roads and footpaths to prevent traffic of the enemy’s soldiers, horse riders, and horse-drawn vehicles.

When the fruit is lying on the ground, at least one thorn is always pointing upwards, so that it may stick to a foot of a passing animal. If a furry animal, like a sheep, lies down in an area with these fruits, several of them will stick to its fleece. In this way, the seeds may be widely dispersed. Much damage has been done to the feet of livestock by these fruits.


Tribulus terrestris Caltrop, puncture vine
A prostrate herb, very variable, branches to 60 cm long, spreading, leaves opposite, pinnately divided, to 5 cm long. The flowers are yellow (sometimes white with yellow centre), to 1.5 cm across. The fruit is to 1 cm across, with 2 long and 2 short, very strong spines, which are able to penetrate a bicycle tyre, giving rise to the popular name puncture vine.

This plant is very widely distributed, from southern Europe eastwards across Central Asia to Japan, southwards to southern Africa, Sri Lanka, and Indochina. It is used medicinally.



Tribulus terrestris, Ulley, Ladakh. (Photo copyright © by Kaj Halberg)




Xanthium Cocklebur
These plants, comprising 2 or 3 species, probably originate in North America, but have become naturalized in most warmer areas of the world.

The generic name is derived from xanthion, the Greek name of rough cocklebur (below), derived from xanthos (‘yellow’). The juice of this plant was formerly utilized to dye the hair yellow. The prefix cockle is unexplained.


Rough cocklebur (Xanthium strumarium)
This plant probably originates in North America, but has become naturalized in most other warmer areas of the world. It easily spreads by its extremely spiny fruits, which attach themselves to animals’ pelts, trousers, etc.

In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes about the cocklebur: “They are very likely to find lodgment in upland fields. The hooks on the bur of the cocklebur are a clever device for seed distribution. Every animal that walks through a patch of cockleburs or even brushes against a single plant, when its seeds are ripe, gives a free ride to as many burry passengers as come in contact with the hair or clothing of that unsuspecting animal. Every hunter and his dog help this culprit over the fences into other fields.”

The Zuni people of south-western United States used this plant for many purposes. The seeds were ground, mixed with cornmeal and made into cakes, which were then steamed. When performing a cactus ceremony, they rubbed chewed seeds onto the body to protect it from the spines. A poultice, containing cocklebur seeds, was applied to wounds or used to remove splinters. (Source: M.C. Stevenson 1915. Ethnobotany of the Zuni Indians. SI-BAE Annual Report No. 30)

The specific name indicates that the plant was formerly used for treatment of struma.



Rough cocklebur with fruits, Lower Marsyangdi Valley, Annapurna, Nepal. (Photos copyright © by Kaj Halberg)




(Uploaded October 2023)