Reynoutria japonica
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''Reynoutria japonica'', synonyms ''Fallopia japonica'' and ''Polygonum cuspidatum'', is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of ...
perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...
in the knotweed and buckwheat family
Polygonaceae The Polygonaceae are a Family (biology), family of flowering plants known Common name, informally as the knotweed family or smartweed—buckwheat family in the United States. The Botanical name, name is Basionym, based on the genus ''Polygonum'', ...
. Common names include Japanese knotweed and Asian knotweed. It is native to
East Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...
in
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
and
Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...
. In
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
and
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
, the species has successfully established itself in numerous habitats, and is classified as a pest and
invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
in several countries. The plant is popular with beekeepers, and its young stems are edible, making it an increasingly popular foraged vegetable with a flavour described as
lemon The lemon (''Citrus'' × ''limon'') is a species of small evergreen tree in the ''Citrus'' genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some ...
y
rhubarb Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. ...
.


Description

The
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s are small, cream or white, produced in erect
raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...
s long in late summer and early autumn. Japanese knotweed has hollow stems with distinct raised
node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics * Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines ...
s that give it the appearance of
bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...
, though it is not related. While stems may reach a maximum height of each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down. The
leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
are broad oval with a truncated base, long and broad, with an entire margin. New leaves of ''Reynoutria japonica'' are dark red and long; young leaves are green and rolled back with dark red veins; leaves are green and shaped like a heart flattened at the base, or a shield, and are usually around long. Mature ''R.japonica'' forms , dense thickets. Leaves shoot from the stem nodes alternately in a zigzag pattern. Plants that are immature or affected by mowing and other restrictions have much thinner and shorter stems than mature stands, and are not hollow. File:WEEDS054.jpg, Dead stems from previous years remain in place as new growth appears. File:Caersws headg row1.jpg, A hedgerow made up of
rose A rose is either a woody perennial plant, perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivar ...
s and Japanese knotweed File:Knotweed054.jpg, Erect inflorescence


Identification

Japanese knotweed may be confused with other plants suspected of being knotweed owing to the similar appearance of leaves and stems.
Dogwood ''Cornus'' is a genus of about 30–60 species of woody plants in the family Cornaceae, commonly known as dogwoods or cornels, which can generally be distinguished by their blossoms, berries, and distinctive bark. Most are deciduous ...
,
lilac ''Syringa'' is a genus of 12 currently recognized species of flowering woody plants in the olive family or Oleaceae called lilacs. These lilacs are native to woodland and scrub from southeastern Europe to eastern Asia, and widely and commonly ...
, houttuynia (''Houttuynia cordata''), ornamental bistorts such as red bistort ('' Persicaria amplexicaulis)'', lesser knotweed ('' Koenigia campanulata''), Himalayan balsam (''
Impatiens glandulifera ''Impatiens glandulifera'', Himalayan balsam, is a large annual plant native to the Himalayas. Via human introduction it is now present across much of the Northern Hemisphere and is considered an invasive species in many areas. Uprooting or cutt ...
''), broad-leaved dock (''
Rumex obtusifolius ''Rumex obtusifolius'', commonly known as bitter dock, broad-leaved dock, bluntleaf dock, dock leaf, dockens or butter dock, is a perennial plant in the family Polygonaceae. It is native to Europe, but is found on all temperate continents. It i ...
''), bindweed (''
Convolvulus arvensis ''Convolvulus arvensis'', or field bindweed, is a species of bindweed in the Convolvulaceae native to Europe and Asia. It is a rhizomatous and climbing or creeping herbaceous perennial plant with stems growing to in length. It is usually found a ...
''),
bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...
, Himalayan honeysuckle ('' Leycesteria formosa''), and Russian vine ('' Fallopia baldschuanica'') have been suspected of being ''Reynoutria japonica''.


Uses

Japanese knotweed flowers are valued by some beekeepers as an important source of nectar for honeybees, at a time of year when little else is flowering. Japanese knotweed yields a monofloral honey, usually called ''bamboo honey'' by northeastern U.S.
beekeeper A beekeeper is a person who keeps honey bees, a profession known as beekeeping. The term beekeeper refers to a person who keeps honey bees in beehives, boxes, or other receptacles. The beekeeper does not control the creatures. The beekeeper ow ...
s, like a mild-flavored version of
buckwheat Buckwheat (''Fagopyrum esculentum'') or common buckwheat is a flowering plant in the knotweed family Polygonaceae cultivated for its grain-like seeds and as a cover crop. Buckwheat originated around the 6th millennium BCE in the region of what ...
honey (a related plant also in the Polygonaceae). The young stems are edible as a spring
vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...
, with a flavour similar to
rhubarb Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. ...
. In some locations, semi-cultivating Japanese knotweed for food has been used as a means of controlling knotweed populations that invade sensitive wetland areas and drive out the native vegetation. It is eaten in Japan as ''
sansai is a Japanese language, Japanese word literally meaning "mountain vegetables", originally referring to vegetables that grew naturally, were foraged in the wild, and not grown and harvested from fields. However, in modern times, the distinctio ...
'' or wild foraged vegetable. In Europe, young shoots have been used in restaurant cuisine. Knotweed can grow up to 30 cm per day, hence it is a fast-growing vegetable tolerant of poor quality soils. Because knotweed is resistant to over-harvesting, it is more often foraged than cultivated as a vegetable. The plant can be eaten raw or cooked. Ground-feeding songbirds and gamebirds also eat the seeds. Rhizome of ''R. japonica'' is the source of
lactoperoxidase Lactoperoxidase (LPO, ) is a peroxidase enzyme secreted from mammary, salivary, tears and other mucosal glands including the lungs, bronchii and nose that function as a natural, first line of defense against bacteria and viral agents. Lactoperox ...
peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system.


In Japan

It grows widely throughout Japan and is foraged as a wild edible vegetable (''
sansai is a Japanese language, Japanese word literally meaning "mountain vegetables", originally referring to vegetables that grew naturally, were foraged in the wild, and not grown and harvested from fields. However, in modern times, the distinctio ...
''), though not in sufficient quantities to be included in statistics. They are called by such regional names as ''tonkiba'' ( Yamagata), ''itazuiko'' ( Nagano, Mie), ''itazura'' (
Gifu is a Cities of Japan, city located in the south-central portion of Gifu Prefecture, Japan, and serves as the prefectural capital. The city has played an important role in Japan's history because of its location in the middle of the country. Durin ...
, Toyama,
Nara The National Archives and Records Administration (NARA) is an independent agency of the United States government within the executive branch, charged with the preservation and documentation of government and historical records. It is also task ...
, Wakayama, Kagawa), ''gonpachi'' ( Shizuoka, Nara, Mie, Wakayama), ''sashi'' ( Akita, Yamagata), ''jajappo'' ( Shimane, Tottori, Okayama), ''sukanpo'' (many areas). Young leaves and shoots, which look like asparagus, are used. They are extremely sour; the fibrous outer skin must be peeled, soaked in water for half a day raw or after parboiling, before being cooked.


Invasive species

This species is listed by the
World Conservation Union The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the statu ...
as one of the world's worst invasive species. It is a frequent colonizer of
temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
s, roadsides, and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States. The success of the species has been partially attributed to its tolerance of a very wide range of conditions, including drought, different soil types, variable soil pH, and high salinity. Its
rhizomes In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
can survive temperatures of and can extend horizontally and deep, making removal by excavation extremely difficult. The plant is also resilient in response to cutting, vigorously resprouting from the roots.


Impact

Japanese knotweed has a strong and extensive root system that can penetrate through the cracks of hard surfaces such as concrete, asphalt, and brick. As the plant grows, it can cause significant damage to building foundations, walls, and drainage systems, which can be very costly to repair. Its invasive roots can also damage concrete foundations, buildings, roads, paving, retaining walls, and architectural sites. Additionally, the plant's dense growth can impede water flow, increasing the risk of flooding by reducing the capacity of flood channels to carry water. Recent reporting suggests that Japanese knotweed is not nearly as destructive to structures as once thought. Damage appears to only occur at or near areas that were already compromised. Japanese knotweed shades out other
vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...
, grows over buildings and other structures, encourages fire, and damages paved surfaces.


Control

Japanese knotweed has a large underground network of roots (rhizomes). To eradicate the plant the roots need to be killed. All above-ground portions of the plant need to be controlled repeatedly for several years in order to weaken and kill the entire patch. Picking the right herbicide is essential, as it must travel through the plant and into the root system below. But also more ecologically friendly means are being tested as an alternative to chemical treatments.


Chemical

The abundance of the plant can be significantly reduced by applying
glyphosate Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by EPSP inhibitor, inhibiting the plant enzyme 5-en ...
, imazapyr, a combination of both, or by cutting all visible stalks and filling the stems with glyphosate. However, these methods have not been proven to provide reliable long-term results in eliminating the treated population.


Mechanical

Digging up the rhizomes is a common solution where the land is to be developed, as this is quicker than the use of herbicides, but safe disposal of the plant material without spreading it is difficult; knotweed is classed as controlled waste in the UK, and disposal is regulated by law. Digging up the roots is also very labour-intensive and not always effective. The roots can extend up to deep, and leaving even just a few centimetres (inches) of root behind will result in the plant quickly growing back. Covering the affected patch of ground with a non-translucent material can be an effective follow-up strategy. However, the trimmed stems of the plant can be razor sharp and are able to pierce through most materials. Covering with non-flexible materials such as concrete slabs has to be done meticulously and without leaving even the smallest splits. The slightest opening can be enough for the plant to grow back.
Soil steam sterilization Soil steam sterilization (soil steaming) is a farming technique that Sterilization (microbiology), sterilizes soil with steam in open fields or greenhouses. Pests of plant cultures such as weeds, bacteria, fungi and viruses are killed through ...
involves injecting steam into contaminated soil in order to kill subterranean plant parts. Trials in
Haida Gwaii Haida Gwaii (; / , literally "Islands of the Haida people"), previously known as the Queen Charlotte Islands, is an archipelago located between off the British Columbia Coast, northern Pacific coast in the Canadian province of British Columbia ...
,
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
, using sea water sprayed on the foliage, have not demonstrated promising results.


Biological

Research has been carried out on a '' Mycosphaerella'' leaf spot fungus, which devastates knotweed in its native Japan. This research has been relatively slow due to the complex life cycle of the fungus. Following earlier studies, imported Japanese knotweed
psyllid Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants ( ...
insects '' Aphalara itadori'', whose only food source is Japanese knotweed, were released at a number of sites in Britain in a study running from 1 April 2010 to 31 March 2014. In 2012, results suggested that establishment and population growth were likely, after the insects overwintered successfully. In 2020
Amsterdam Amsterdam ( , ; ; ) is the capital of the Netherlands, capital and Municipalities of the Netherlands, largest city of the Kingdom of the Netherlands. It has a population of 933,680 in June 2024 within the city proper, 1,457,018 in the City Re ...
imported and released 5,000 Japanese ''Aphalara itadori'' leaf fleas, exempting them from a strict ban on the introduction of alien species, as one of the measures to contain the knotweed. The psyllids suck up sap from the plant, potentially killing young shoots and slowing or even stopping growth. It was hoped that the psyllid would hibernate over winter and establish themselves in 2021. Anecdotal reports of effective control describe the use of goats to eat the plant parts above ground followed by the use of pigs to root out and eat the underground parts of the plant.


Impact of the plant outside its area of origin


New Zealand

Japanese knotweed is classed as an unwanted organism in
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
and is established in some parts of the country.


Europe

European adventurer
Philipp Franz von Siebold Philipp Franz Balthasar von Siebold (17 February 1796 – 18 October 1866) was a German physician, botanist and traveller. He achieved prominence by his studies of Japanese flora (plants), flora and fauna (animals), fauna and the introduction of ...
transported Japanese knotweed from a Japanese volcano to
Leiden Leiden ( ; ; in English language, English and Archaism, archaic Dutch language, Dutch also Leyden) is a List of cities in the Netherlands by province, city and List of municipalities of the Netherlands, municipality in the Provinces of the Nethe ...
Netherlands. By 1850, a specimen from this plant was donated by Von Siebold to the
Royal Botanic Gardens, Kew Royal Botanic Gardens, Kew is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. An internationally important botanical research and education institution, it employs 1,10 ...
. It was favoured by gardeners because it looked like bamboo and grew everywhere. Ann Conolly provided the first authoritative work on the history and distribution of the plant in the UK and Europe in the 1970s. According to ''The Daily Telegraph'', the weed has travelled rapidly, aided by rail and water networks. In the UK, Japanese knotweed is a single female clone. However, it is able to readily hybridise with related species. In the UK, Japanese knotweed is established in the wild in many parts of the country and creates problems due to the impact on biodiversity, flood management and damage to property. It is an offence under section 14(2) of the
Wildlife and Countryside Act 1981 The Wildlife and Countryside Act 1981 (c. 69) is an act of Parliament in the United Kingdom implemented to comply with European Council Directive 79/409/EEC on the conservation of wild birds. In short, the act gives protection to native species ...
to "plant or otherwise cause to grow in the wild" any plant listed in Schedule nine, Part II to the Act, which includes Japanese knotweed. As of 2014, householders and landlords in residential areas who do not control the plant in their gardens, can receive an on-the-spot fine or be prosecuted. It is also classed as "controlled waste" in Britain under part 2 of the
Environmental Protection Act 1990 The Environmental Protection Act 1990 (c. 43) (initialism: EPA) is an Act of the Parliament of the United Kingdom that defines, within England and Wales and Scotland, the fundamental structure and authority for waste management and control of e ...
. This requires disposal at licensed landfill sites. Some home owners in the United Kingdom are unable to sell their homes if there is any evidence of knotweed on the property. The species is expensive to remove. It cost £70 million to eradicate knotweed from 10 acres of the London 2012 Olympic Games velodrome and aquatic centre. Defra's Review of Non-native Species Policy states that a national eradication programme would be prohibitively expensive at £1.56 billion. The Centre for Ecology and Hydrology has been using
citizen science The term citizen science (synonymous to terms like community science, crowd science, crowd-sourced science, civic science, participatory monitoring, or volunteer monitoring) is research conducted with participation from the general public, or am ...
to develop a system that gives a knotweed risk rating throughout Britain. The decision was taken on 9 March 2010 in the UK to release into the wild a Japanese
psyllid Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants ( ...
insect, '' Aphalara itadori''. Its diet is highly specific to Japanese knotweed and shows good potential for its control. Controlled release trials began in South Wales in 2016. In Scotland, the Wildlife and Natural Environment (Scotland) Act 2011 came into force in July 2012, superseding the Wildlife and Countryside Act 1981. This act states that is an offence to spread, intentionally or unintentionally, Japanese knotweed (or other invasive species). In
Northern Ireland Northern Ireland ( ; ) is a Countries of the United Kingdom, part of the United Kingdom in the north-east of the island of Ireland. It has been #Descriptions, variously described as a country, province or region. Northern Ireland shares Repub ...
, it has been recorded from Counties Down, Antrim and Londonderry. The earliest record is in 1872. In the
Republic of Ireland Ireland ( ), also known as the Republic of Ireland (), is a country in Northwestern Europe, north-western Europe consisting of 26 of the 32 Counties of Ireland, counties of the island of Ireland, with a population of about 5.4 million. ...
, it has been recorded from
Howth Head Howth Head ( ; ''Ceann Bhinn Éadair'' in Irish) is a peninsula northeast of the city of Dublin in Ireland, within the governance of Fingal County Council. Entry to the headland is at Sutton while the village of Howth and the harbour are on t ...
, County Dublin at Doldrum Bay.


United Kingdom lending controversy

In the United Kingdom, Japanese knotweed has received a lot of attention in the press as a result of very restrictive lending policies by banks and other mortgage companies. Several lenders have refused mortgage applications on the basis of the plant being discovered in the garden or neighbouring gardens. The
Royal Institution of Chartered Surveyors The Royal Institution of Chartered Surveyors (RICS) is a global professional body for those working in the Built Environment, Construction, Land, Property and Real Estate. The RICS was founded in London in 1868. It works at a cross-governmental ...
published a report in 2012 in response to lenders refusing to lend "despite notweedbeing treatable and rarely causing severe damage to the property". In response to this guidance, several lenders have relaxed their criteria in relation to discovery of the plant. As recently as 2012, the policy at the Woolwich (part of Barclays plc) was "if Japanese knotweed is found on or near the property then a case will be declined due to the invasive nature of the plant." Their criteria have since been relaxed to a category-based system depending on whether the plant is discovered on a neighbouring property (categories 1 and 2) or the property itself (categories 3 and 4) incorporating proximity to the property
curtilage In common law, the curtilage of a house or dwelling is the land immediately surrounding it, including any closely associated buildings and structures, but excluding any associated " open fields beyond". In feudal times every castle with its depen ...
and the main buildings. Even in a worst-case scenario (category 4), where the plant is "within 7 metres (23 feet) of the main building, habitable spaces, conservatory and/or garage and any permanent outbuilding, either within the curtilage of the property or on neighbouring land; and/or is causing serious damage to permanent outbuildings, associated structures, drains, paths, boundary walls and fences" Woolwich lending criteria now specify that this property may be acceptable if "remedial treatment by a Property Care Association (PCA) registered firm has been satisfactorily completed. Treatment must be covered by a minimum 10-year insurance-backed guarantee, which is property specific and transferable to subsequent owners and any mortgagee in possession." Santander have relaxed their attitude in a similar fashion. In 2022 the Royal Institution of Chartered Surveyors produced updated guidance for assessing knotweed. Since the 2012 RICS report much more information on the risks from Japanese knotweed have been gained. One important change is that the distance of a plant from a property to be considered a problem has been reduced to 3 metres (10 feet). Property Care Association chief executive Steve Hodgson, whose trade body has set up a task force to deal with the issue, said: "Japanese knotweed is not 'house cancer' and could be dealt with in the same way qualified contractors dealt with faulty wiring or damp."


United States

The weed can be found in 42 of the 50 United States.


Canada

According to Gail Wallin, executive director of the Invasive Species Council of B.C., and co-chair of the Canadian Council on Invasive Species, by 2015 it was found in all provinces in Canada except Manitoba and Saskatchewan. In Vancouver plants went under "four lanes of highway and have popped up on the other side." At Mission Point Park in Davis Bay, British Columbia, municipal crews attempted to eradicate it by digging out the plant to a depth of about three metres (10 feet) with an excavator. It grew back twice as large the next year. To avoid an epidemic as in the United Kingdom, some provinces in Canada are pushing for relaxation of provincial limits on the use of herbicides close to waterways so knotweed can be aggressively managed with strong chemicals. In spite of its status as an invasive species it is still sometimes sold or swapped in Canada as an edible "false bamboo". Bohemian knotweed, a hybrid between Japanese and giant knotweed that produces huge quantities of viable seeds, now accounts for about 80 per cent of knotweed infestations in British Columbia.


Common names

Common names for Japanese knotweed include fleeceflower, Himalayan fleece vine, billyweed, monkeyweed, monkey fungus, elephant-ear bamboo, pea shooters, donkey rhubarb, American bamboo, and Mexican bamboo, among many others, depending on country and location. In Japanese, the name is , which uses the same ''
kanji are logographic Chinese characters, adapted from Chinese family of scripts, Chinese script, used in the writing of Japanese language, Japanese. They were made a major part of the Japanese writing system during the time of Old Japanese and are ...
'' as the Chinese name ''huzhang'' (虎杖), meaning "tiger staff".


See also

* Chinese knotweed * '' Persicaria capitata'' for another plant species called Japanese knotweed


Explanatory notes


References


External links


Species Profile - Japanese knotweed (''Fallopia japonica'')
National Invasive Species Information Center,
United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Locate ...
, 2020
Japanese knotweed
University of Minnesota Extension, 2023
The alien shrub that can't be stopped
– BBC Future, 2022 {{Authority control Flora of China Flora of Eastern Asia Garden plants of Asia Medicinal plants Plants described in 1777 Polygonoideae Stem vegetables