Pinkweeds, smartweeds, and knotweeds

 

 

 

 

 

 

 

 

 

 

 

The name pinkweed alludes to the flower colour of many of these plants, whereas smartweed refers to water pepper (Persicaria hydropiper, below), whose leaves have a peppery taste, which may ‘smart’ your mouth. Smart is an old English word, adapted from German Schmerz, which means ‘pain’. The term knotweed alludes to several creeping species, which often form a dense tangle, a ‘knot’.

Formerly, they were all lumped in the genus Polygonum. However, morphological and genetic research have had the effect that most of them have been transferred to various other genera, including Bistorta, Fallopia, Koenigia, Persicaria, and Reynoutria, which are all presented below, together with Polygonum.

These plants are found almost worldwide.

 

The generic name is derived from the Latin bis (‘twice’) and tortus (‘twisted’), like the English name snake-root referring to the twisted root of the common bistort (B. officinalis, below).

 

It is quite common on open slopes and in rocky areas, from Afghanistan eastwards through southern Tibet and northern Himalaya to Myanmar, growing at elevations between 3,000 and 4,900 m.

In Nepal, the rhizome is used for brewing tea, and also taken for stomach disorders.

The specific name is Latin, meaning ‘kindred’, presumably of another plant.

 

 

 

 

 

 

 

It has a wide range, found from Afghanistan eastwards along the Himalaya to central China, growing in shrubberies, forest edges, and open slopes.

In Nepal, the rhizome is utilized for tea, and a paste of the plant is applied to wounds.

The specific name refers to the upper leaves clasping the stem, from the Latin amplexus (‘clasped’) and‎ caulis (‘stem’).

 

 

 

 

 

 

 

 

 

It is distributed from Uttarakhand, north-western India, eastwards to Bhutan and thence northwards to central China, growing in grasslands and on open slopes at altitudes between 1,700 and 5,000 m, mainly in drier areas.

In Nepal, juice of the root is used for diarrhoea and dysentery.

The specific name is derived from Ancient Greek makros (‘long’) and phyllon (‘leaf’), presumably alluding to the leaves being rather long, compared to the width.

 

 

 

 

 

This species is widespread in temperate areas of central and southern Europe, including the British Isles, eastwards to the Pacific, southwards to Morocco, Iran, and southern China. It is also a common escape in North America. In southern Europe, it is restricted to mountains. It is very common in the Alps, growing in meadows and pastures, at forest edges, and along trails, up to altitudes of about 2,100 m.

Fresh leaves are a valuable fodder, whereas they crumble if they are preserved as hay. The rhizome contains an edible starch, and the leaves were formerly used in folk medicine to treat wounds.

Popular names of this plant include meadow bistort and pudding grass, the latter referring to an old usage of the leaves in northern England as an ingredient in a bitter Lent pudding, together with other herbs, oatmeal, and eggs.

 

 

 

 

 

 

 

It is found from Kashmir eastwards to Bhutan and south-eastern Tibet, growing at elevations between 3,000 and 4,500 m. It is common in wetter areas of Nepal.

In Nepal, juice of the root is utilized for fever.

The specific name is Latin, meaning ‘with leaves like Vaccinium‘ (blueberry).

 

 

 

 

 

 

 

 

 

This plant is widely distributed in subarctic and temperate areas of the Northern Hemisphere, southwards to Arizona, Spain, the Caucasus, the Himalaya, and northern Indochina.

In Nepal, the root is used for fever, seeds for cough and infections. The seeds are roasted and pickled.

The specific name is derived from the Latin vivus (‘alive’) and‎ pario (‘I bear’, i.e. offspring), alluding to the bulbils in the lower part of the spike.

 

 

 

 

 

 

 

 

 

The generic name probably honours Italian botanist and anatomist Gabriele Falloppio (1523-1562), who was superintendent of the botanical garden at Padua.

 

Black bindweed mostly grows on disturbed or cultivated land, and it may sometimes be a noxious weed. It is widely distributed in temperate areas of Eurasia, southwards to northern Africa, the Himalaya, and northern Indochina. In the northern parts of its range it is found down to sea level, whereas in the southern parts it is restricted to mountains. In China, it has been observed up to an elevation of 3,600 m. It has become naturalized in many other areas of the world.

The seeds are edible. Remains have been found in Bronze Age middens, indicating that it was a food crop in those days.

The specific name refers to its climbing habit and the shape of the leaves, by which it resembles bindweeds, genus Convolvulus (see page Plants: Morning glories and bindweeds on this website).

 

 

 

 

 

 

 

 

 

In Nepal, the slightly acid stems of some members are chewed when young.

The generic name commemorates Baltic-German botanist and physician Johann Gerhard König (1728-1785), a pupil of Swedish naturalist Carl Linnaeus (1707-78) in 1757. While living in Denmark 1759-67, he examined the plants of Iceland. Later, he served in the Danish Tranquebar Mission in South India, before serving under the Nawab of Arcot, and later the English East India Company. He collected many plants from the region.

 

It is widely distributed, from southern and eastern Europe eastwards across the Middle East and Central Asia to the Pacific Ocean, southwards to Iran, the Himalaya, and northern Indochina, growing in shrubberies, on open slopes, and along streams.

The stem is edible when cooked.

 

 

 

 

 

 

 

It is found from Uttarakhand, north-western India, eastwards to northern Myanmar and south-western China, growing in open forests and shrubberies, and along streams.

In Nepal, tender parts are cooked as a vegetable.

The specific name was given in allusion to the bell-shaped flowers, from the Latin campanula (’little bell’).

 

 

 

 

 

This plant is widespread in subarctic regions, extending into temperate areas southwards to Arizona, the British Isles, Pakistan, Ladakh, and western China. It grows in humid grasslands and along streams.

The specific name refers to Iceland, where König (see generic name above) first collected this species in 1765.

 

 

 

 

 

It is distributed from Uttarakhand, north-western India, eastwards to southern China, and thence southwards through Indochina to Indonesia.

In Nepal, tender parts are cooked as a vegetable, and also pickled.

The specific name is Latin, meaning ‘soft’ or ‘delicate’, alluding to the downy-hairy stems and leaves.

 

 

 

 

 

 

 

It grows in forests and open areas, and at streamsides, from Afghanistan eastwards to northern Myanmar and south-western China, found at elevations between 2,000 and 4,500 m.

In Nepal, tender parts are cooked as a vegetable.

This species was previously known as Persicaria polystachya, Persicaria wallichii, or Polygonum wallichii.

 

 

 

 

 

 

 

 

 

This species is distributed in dry and stony regions, from Afghanistan eastwards across northern Pakistan, Ladakh, and Tibet to northern Nepal and northern Arunachal Pradesh, found at elevations between 3,300 and 5,600 m.

It is used medicinally for dysentery.

The specific name is derived from the Latin tortus (‘twisted’) and osus (‘plenty’), referring to the twisted leaves.

 

 

 

 

 

 

 

 

 

The generic name is derived from the Latin persica (‘peach-like’), alluding to the leaves of some members resembling peach leaves.

 

It is native to subarctic and temperate areas of the Northern Henisphere, southwards to Central America, Arabia, and China, and also occurs in Ethiopia, Kenya, and South Africa.

The specific name is derived from the Greek amfi (‘both sides’) and bios (‘life’), thus ‘living on both sides’, referring to the fact that the plant is found in water as well as on dry land.

 

 

 

 

 

 

 

 

 

 

 

 

 

It is distributed from Pakistan eastwards to Taiwan, southwards to Sri Lanka and northern Malaysia, growing in a variety of habitats, including rocks, stone fences, and open slopes, and along trails, found at elevations between 600 and 3,500 m.

In Nepal, a paste of the plant is applied to boils and wounds, and its juice is taken for stomach problems. The plant is collected for fodder.

The specific name is Latin, meaning ‘forming a head’, alluding to the globular inflorescence.

 

 

 

 

 

 

 

 

 

This species grows in forests, shrubberies, and on open slopes, from sea level to an altitude of about 3,000 m. It is distributed from Pakistan eastwards to Korea and Japan, southwards to Sri Lanka, Indonesia, and the Philippines.

 

 

 

 

 

 

 

 

 

 

 

It is partial to wet areas, growing along streams and in marshes. It is very widely distributed in warmer regions, in south-eastern United States, Mexico, Central America, and in large parts of South America, in Sudan and Ethiopia, and the Arabian Peninsula, and from Pakistan eastwards to Taiwan, southwards to Sri Lanka, Indochina, and the Philippines.

 

 

 

 

 

Very widely distributed, found from the entire Europe eastwards across Central Asia to the Pacific Ocean, southwards to North Africa, Iran, Sri Lanka, Indonesia, and Australia. It grows in wet meadows, and along rivers and ponds.

In Nepal, the plant is boiled, and the filtered water is taken to expel intestinal parasites. The plant is also strewn in water to stupefy fish.

The specific name is derived from Ancient Greek hydor (‘water’) and peperi (‘pepper’), ultimately from Sanskrit pippali. It refers to the leaves, which have a strong peppery taste, also reflected in the name smartweed, derived from old English smeortan (‘to cause pain’), originally from German Schmerz (‘pain’). In his delightful book All about Weeds, American botanist Edwin Spencer (1881-1964) writes: “There are a great many species (…) which look somewhat like this weed, but most of them lack the ‘smart’ taste entirely, and none of them possess the fire of hydropiper.”

 

 

 

 

 

 

 

It is an annual, stem to about 90 cm tall, green or reddish, smooth or downy-haired, swollen at the nodes. Leaves almost sessile, lanceolate or narrowly elliptic, to 15 cm long and 3 cm wide, the upperside often with a dark blotch in the centre, margin hairy. The sheath is brownish or transparent, to 3 cm long, sometimes fringed with a few hairs above. The inflorescences are terminal or axillary, dense spikes, erect or nodding, to 8 cm long, often with several spikes close together, forming what looks like a loose panicle. Corolla pink or white, petals to 3 mm long.

The young leaves are edible raw, and in some areas young plants are cooked as a vegetable. Medicinally, it is used as an astringent, and for inflammation, stomach problems, and fever. The plant produces a soft, white, soap-like mass, used for bathing and washing clothes.

The specific name is derived from the Latin lapathi, an old name for docks or sorrels (which, however, belong to the closely related genus Rumex), and folius (‘leaf’). The name smartweed alludes to its similarity to the ‘true’ smartweed, P. hydropiper (above).

This species is very similar to the following one, and telling them apart is far from easy. A detailed identification key is found in this article: M. Wilcox, 2021. Recording Persicaria maculosa and P. lapathifolia (Polygonaceae). British & Irish Botany 3(3): 349-361, web version Wilcox+Final.pdf.

 

 

 

 

 

 

 

It is native to temperate and subtropical regions of Eurasia and northern Africa, but has become naturalized in numerous countries across the globe.

The specific name is Latin, meaning ‘spotted’, referring to numerous glands on the underside of the leaves – which, however, are often insignificant and hard to see.

 

 

 

 

 

It grows in many habitats, including streamsides, roadsides, and wastelands. As its specific name implies, it is an eastern species, occurring naturally from the Indian Subcontinent eastwards to Taiwan, and thence northwards to Ussuriland (south-eastern Siberia), southwards to the Philippines, Indonesia, New Guinea, and eastern Australia. However, it is widely cultivated and has become naturalized in numerous countries around the world.

Medicinally, it has a wide range of uses, including treating rheumatism, promoting digestion, aiding diuresis, and activating blood circulation. It is also used against inflammation and diarrhoea.

 

 

 

 

 

This plant grows in shrubberies and open areas, and along trails and roads. It is very widely distributed, from Turkey and the Caucasus eastwards to Ussuriland (south-eastern Siberia), China, Korea, Japan, Taiwan, the Indian Subcontinent, Indochina, Indonesia, New Guinea, and the Philippines. It has also been accidentally introduced elsewhere and has become naturalized in many places. In North America and Europe, it is regarded as an invasive species.

Ripe fruits are edible. In Nepal, tender parts are cooked as a vegetable, and juice of the leaves is taken for backache. It is also used for various purposes in traditional Chinese medicine. The foliage provides good fodder, and stems can be used to make ropes.

The specific name is a botanical term, used when the stem seemingly passes through the leaf blade, from the Latin per (‘through’) and foliatus (‘leafy’), in this case alluding to the leaf-like ears at the nodes. Common names include mile-a-minute vine, which alludes to the rapid growth of the plant, and devil’s tail and climbing tearthumb, which both refer to its vicious prickles.

 

 

 

 

 

 

 

It is distributed from the Indian Subcontinent eastwards to China, Korea, Japan, and Taiwan, and thence southwards to Indonesia, growing in shrubberies and open areas, and along fields and streams.

In Nepal, it is strewn in streams to stupefy fish.

The specific name is Latin, meaning ‘downy-hairy’ – not a descriptive name!

This species resembles Persicaria hydropiper (above), but may be identified by the stem and the inflorescence, which are both often red.

 

 

 

 

 

It is found in grasslands, shrubberies, and open humid slopes, from Uttarakhand, north-western India, eastwards to eastern China and Taiwan, and thence southwards to Java and the Philippines.

In Nepal, young parts are cooked as a vegetable.

The botanical meaning of the specific name is ‘pointing backwards from the tip’, alluding to the lobes on the leaves.

 

 

 

 

 

This plant grows in forests and shrubberies, and on open slopes, found up to elevations around 1,500 m. It is distributed from Ussuriland (south-eastern Siberia), southwards through eastern China, Korea, Japan, and Taiwan to northern Vietnam.

Young parts may be cooked as a vegetable.

The specific name is derived from the Latin sentis (‘thorn’) and osus (‘full of’) – a descriptive name!

 

 

 

 

 

The generic name is explained at the top of this page. The common names allude to the fact that these plants often form a dense tangle, a ‘knot’.

 

The specific name is derived from the Latin arena (‘sand’), thus ‘of the sand’, i.e. ‘growing in sand’.

 

 

 

 

 

Prostrate knotweed is very variable, and in its widest sense it contains a number of species or subspecies, including arenastrum (above). It is branched from the base, stems mostly creeping, but occasionally ascending, growing to 70 cm long/tall, sometimes more. Leaves are numerous, short-stalked, linear, lanceolate, or elliptic, on the main stem to 4 cm long and 1.2 cm wide, smaller on the branches, margin entire, tip pointed or rounded. The small flowers, to 4 mm across, are solitary or in small clusters at the nodes, corolla white or pinkish, often with a greenish base.

This species is eagerly eaten by cows and chickens, and the seeds are much relished by small birds. This was observed by Swedish naturalist Carl Linnaeus (1707-78), when he named the plant aviculare, derived from the Latin avicula (‘small bird’).

In folk medicine, the juice has been used to stop nose-bleed and other types of bleeding. Tea made from the plant was used for diarrhoea, cough, bronchitis, and bleeding haemorrhoids.

In his play A Midsummer Night’s Dream, William Shakespeare (1564-1616) calls this plant “the hindering knotgrass”. In those days, it was believed that its juice would interfere with the growth of young children and domestic animals.

 

 

 

 

 

 

 

This species is found in South and East Asia, Indochina, the Philippines, Australia, most of Africa, and Madagascar, growing in dry rice fields and humid grasslands, and along trails.

In Nepal, the plant is boiled, and the juice taken for dysentery, juice of the root for stomach trouble. Tender parts are cooked as a vegetable.

 

 

 

 

 

The generic name commemorates Charles de Saint Omer (1533-1569), Lord of Reynoutre. Flemish botanist Matthias van Lobel (1538-1616) testifies “dat dezelve aan de Kruidkunde zeer veel dienft gedaan heeft.” (‘that the same to Herbology has done much service’).

 

This large plant may grow to 4 m tall, but under harsh conditions it is often much smaller (see upper photo below). It has hollow stems with distinct nodes, making it resemble bamboo. The leaves are broadly ovate, to 14 cm long and 9 cm wide, base mostly truncate, but varies a great deal, margin entire. The small flowers, white or cream-coloured, are arranged in racemes, to 15 cm long. The spathulate, notched fruits are white, cream-coloured, or pink.

Japanese knotweed was introduced to Europe and North America in the 1800s and soon became a popular garden plant because of its bamboo-like appearance, vigorous growth, and pretty inflorescences. However, it quickly turned into a menace, as it spread beyond control, its strong root system being able to “damage concrete foundations, buildings, flood defences, roads, paving, retaining walls, and architectural sites.” (Source: gardenroots.co.uk)

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

 

 

 

 

 

 

 

 

 

It is very similar to the previous species, but has larger leaves, to 40 cm long and 28 cm broad, with almost heart-shaped base and a wavy margin. The shoots are tender and edible.

This species was also introduced to Europe, and during a drought in the 1890s, it was widely used as cattle fodder, as it was little affected by the drought. It was then widely cultivated experimentally, but proved less useful than predicted. Like F. japonica, it has become an invasive weed in many areas.