Polygonum nepalense (Nepal persicaria)

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Flowering habit

Polygonum nepalense (Nepal persicaria); Flowering habit. Table Land, Panchgani, India. August 2010.

©Dinesh Valke/via Flickr - CC BY-SA 2.0

Flowers and foliage

Polygonum nepalense (Nepal persicaria); Flowers and foliage. Table Land, Panchgani, India. August 2010.

©Dinesh Valke/via Flickr - CC BY-SA 2.0

Flowers and foliage

Polygonum nepalense (Nepal persicaria); Flowers and foliage. Table Land, Panchgani, India. August 2010.

©Dinesh Valke/via Flickr - CC BY-SA 2.0

Flowers and foliage

Polygonum nepalense (Nepal persicaria); Flowers and foliage. Table Land, Panchgani, India. August 2010.

©Dinesh Valke/via Flickr - CC BY-SA 2.0

Flowers and foliage

Polygonum nepalense (Nepal persicaria); Flowers and foliage. Table Land, Panchgani, India. August 2010.

©Dinesh Valke/via Flickr - CC BY-SA 2.0

Flowers

Polygonum nepalense (Nepal persicaria); Flowers. Anserma, Colombia. June 2010.

©Hugo Vargas/via Wikimedia Commons - CC BY-SA 4.0

Identity

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Preferred Scientific Name

Polygonum nepalense Meisner (1826)

Preferred Common Name

Nepal persicaria

Other Scientific Names

Persicaria nepalensis (Meisner) H. Gross
Polygonum alatum Sprengel (1827)
Polygonum lyratum Nakai
Polygonum punctatum var. alatum Buch.-Ham. ex D.Don (1825)
Polygonum quadrifidum Hayata

International Common Names

English: snake weed (India)

Local Common Names

Bhutan: berkhey ratnaulo; helepsi; metoshim; shido
Ethiopia: labuche
Germany: Nepalesischer Koeterich
Indonesia: asem tembagan; ganrot; hahaseuman; jukut asam
Japan: tanisoba
Sri Lanka: kangany-machan-pillu

EPPO code

POLAL (Polygonum alatum)
POLNE (Polygonum nepalense)

Taxonomic Tree

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Domain: Eukaryota
Kingdom: Plantae
Phylum: Spermatophyta
Subphylum: Angiospermae
Class: Dicotyledonae
Order: Polygonales
Family: Polygonaceae
Genus: Polygonum
Species: Polygonum nepalense

Notes on Taxonomy and Nomenclature

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Hutchinson et al. (1954) give P. punctatum var. alatum as a synonym (together with P. alatum), while the P. punctatum Buch.-Ham. in southern India, illustrated by Tadulingam et al. (1955), is apparently the same species. P. punctatum Ell. , however, is a quite distinct temperate species (Hafliger and Wolf, 1988). Many Polygonum species, including P. nepalense and P. lapathifolium have recently been re-named as Persicaria species. Hence some modern floras, including Flora of Bhutan (Grierson and Long, 1983), use the name Persicaria nepalensis (Meisner) H. Gross. However, the more familiar older name is retained for the purposes of this Compendium.

Description

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P. nepalense is an annual plant, prostrate to sub-erect, stems simple or branched 15-30(-45) cm high. Leaves are alternate, ovate to elliptic, up to 5 cm long, often with a pair of dark blotches each side of the mid-rib. The lamina is characteristically decurrent, causing the petiole to be effectively winged, and usually auriculate at the base. Foliage is generally glabrous, but punctate with scattered yellow glands on the underside. Ochreae are truncate, 6-10 mm long, sparsely pubescent. The individual flowers, 2-3 mm long, are usually pink, but sometimes white, with four perianth segments. They are carried in dense round clusters up to 1 cm in diameter, sessile or on peduncles up to 5 cm long , singly, or several subtended in upper leaf axils. Seeds are about 2 mm long, trigonous or biconvex, strongly pitted, black.

This description is based largely on Grierson and Long (1983). Everaarts (1981) has especially good drawings.

Distribution

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P. nepalense is believed to have originated in the Himalayas but it is now quite widespread, across the Asian, African and American continents and in the Pacific, but is apparently limited, as a significant weed, to high altitude tropics. Why it does not occur more commonly in temperate lowlands, which have roughly comparable temperature regimes is not clear. It can persist sporadically, in temperate regions, even as far north as the UK but is not reported as a weed problem.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 17 Feb 2021

Continent/Country/Region	Distribution	Invasive	Reference	Notes
Africa
Equatorial Guinea	Present		Hutchinson et al. (1954)
Ethiopia	Present, Widespread		Holm et al. (1979) Stroud and Parker (1989) Denchev and Denchev (2017)
Kenya	Present		Holm et al. (1979) CABI (Undated)
South Africa	Present		Wells et al. (1986)
Tanzania	Present		CABI (Undated)	Original citation: Ivens (1968)
Uganda	Present		CABI (Undated)	Original citation: Ivens (1968)
Asia
Bhutan	Present, Widespread		Grierson and Long (1983) Parker (1992)
China	Present		Guo (1993) CABI (Undated)
-Anhui	Present		CABI (Undated)	Original citation: Wang, 1980
-Fujian	Present		CABI (Undated)	Original citation: Wang, 1980
-Gansu	Present		CABI (Undated)	Original citation: Wang, 1980
-Guangdong	Present		CABI (Undated)	Original citation: Wang, 1980
-Hebei	Present		CABI (Undated)	Original citation: Wang, 1980
-Jiangsu	Present		CABI (Undated)	Original citation: Wang, 1980
-Jilin	Present		CABI (Undated)	Original citation: Wang, 1980
-Liaoning	Present		CABI (Undated)	Original citation: Wang, 1980
-Shaanxi	Present		CABI (Undated)	Original citation: Wang, 1980
-Shanxi	Present		CABI (Undated)	Original citation: Wang, 1980
-Sichuan	Present		CABI (Undated)	Original citation: Wang, 1980
-Tibet	Present		CABI (Undated)	Original citation: Wang, 1980
-Yunnan	Present		CABI (Undated)	Original citation: Wang, 1980
-Zhejiang	Present		CABI (Undated)	Original citation: Wang, 1980
India	Present, Widespread		Tadulingam et al. (1955) Holm et al. (1979)
-Jammu and Kashmir	Present		Kaul (1986) Nimje (1988)
-Sikkim	Present		Grierson and Long (1983)
-Tamil Nadu	Present		Tadulingam et al. (1955)
Indonesia	Present		Holm et al. (1979) Wibowo and Iskandar (2013)
-Java	Present		Everaarts (1981)
-Sulawesi	Present		Everaarts (1981)
-Sumatra	Present		Everaarts (1981)
Japan	Present		Holm et al. (1979)
-Hokkaido	Present		Numata and Yoshizawa (1975)
-Honshu	Present		Numata and Yoshizawa (1975)
-Kyushu	Present		Numata and Yoshizawa (1975)
-Shikoku	Present		Numata and Yoshizawa (1975)
Nepal	Present		Reed (1977)
Philippines	Present		Hafliger and Wolf (1988)
South Korea	Present		Reed (1977) Hwang KiSeon et al. (2015)
Sri Lanka	Present, Widespread		Haigh (1951) Holm et al. (1979)
Taiwan	Present		Reed (1977) Holm et al. (1979)
Europe
Italy	Present, Localized		Webb et al. (1993)
Russia	Present		Reed (1977)
United Kingdom	Present, Localized		Stace (1991)
North America
Mexico	Present	Invasive	Vibrans and Hanan Alipi (2008)
Oceania
Papua New Guinea	Present		Henty and Pritchard (1975)
South America
Colombia	Present		Mena et al. (1978)

Habitat

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P. nepalense has seemingly strict environmental requirements, being largely restricted to the high altitude tropics, from 750-3000 m in Bhutan (Grierson and Long, 1983); 1200-2500 m in southern India (Tadulingam et al., 1955); 1400-2900 m in Ethiopia (Stroud and Parker, 1989) and 1500-2500 m in East Africa (Ivens, 1968). It might be expected to occur also at lower altitudes in temperate areas, but this is rarely so. Where it is common it occurs in a range of disturbed situations, mainly as a weed of annual and perennial crops, around field edges, in the open or in partial shade, usually in moist conditions.

Hosts/Species Affected

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P. nepalense appears to have particular climatic requirements, being very much restricted to high altitude tropics, but within this ecology, it occurs in many, if not most of the crops grown. It is especially abundant in tea, both in India and in East Africa, perhaps encouraged by the repeated use of minimal doses of paraquat which do not provide complete control. It can, however, be predominant in other crops in the absence of any herbicide use. Everaarts (1981) notes that it is one of the commonest weeds of vegetables in highland Java, Indonesia.

Host Plants and Other Plants Affected

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Plant name	Family	Context
Brassica napus var. napus (rape)	Brassicaceae	Other
Camellia sinensis (tea)	Theaceae	Main
Daucus carota (carrot)	Apiaceae	Other
Eragrostis tef (teff)	Poaceae	Other
Hordeum vulgare (barley)	Poaceae	Main
Oryza sativa (rice)	Poaceae	Other
Solanum tuberosum (potato)	Solanaceae	Main
Triticum aestivum (wheat)	Poaceae	Main
Vicia villosa (hairy vetch)	Fabaceae	Other
Zea mays (maize)	Poaceae	Main

Biology and Ecology

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P. nepalense is a relatively short-lived annual, completing development within 4-5 months, though this short period is perhaps partly due to attack by Puccinia polygoni-amphibii (Eden and Bond, 1925). Reproduction is solely by seeds which are produced in great abundance. Eden and Bond (1925) recorded over 30 million seeds/ha, often resulting in complete dominance under suitable conditions in, for example, the highlands of Sri Lanka, southern India and the Himalayas. The reason for its virtual restriction to these highland situations is unexplained. There are no reports of studies on germination behaviour, other than one from Japan indicating 50% viability maintained after 4.5 years storage in soil at 15 cm depth (Watanabe, 1978).

Eden and Bond (1925) indicate that P. nepalense is 'not particularly tolerant of shade' but its predominance in tea must suggest that it has some shade tolerance. The same authors studied the balance between P. nepalense and other weeds under different fertilizer regimes and showed that this species has a lower optimum phosphate level, and that addition of high phosphorus levels encouraged other weeds more and reduced the dominance of P. nepalense.

Everaarts (1981) indicates that P. nepalense prefers not too dry soils in open or lightly shaded situations and is favoured by high soil fertility.

Natural enemies

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Natural enemy	Type	Life stages	Specificity	References	Biological control in	Biological control on
Puccinia polygoni-amphibii	Pathogen
Ustilago polygoni-alati	Pathogen

Impact

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P. nepalense is a weed which apparently only thrives in high altitude tropics but in these areas can become dominant. It is listed by Holm et al. (1979) as a 'principal' or 'serious' weed in Ethiopia, Sri Lanka and India. It is noted as being one of the six most prominent weeds of potato in the Nilgiri Hills of southern India (Nimje, 1988), one of the most important weeds of maize and potato in the 'dry subtropical' and warm and cool temperate zones between 1200 and 2400 m in Bhutan (Parker, 1992) and one of the three most aggressive weeds of wheat in Ethiopia (Gebre et al., 1987). Comparably, in Colombia, it was one of the predominant weeds of carrot on the altiplano de Pasto (Mena et al., 1984). In Indonesia, Everaarts (1981) refers to it as 'one of the commonest and troublesome weeds' of vegetables in highland Java at 1100-2300 m.

There are no reports on the competitive effect of P. nepalense and it has sometimes been regarded as relatively non-competitive in tea, to the point that it may be encouraged as a ground cover to suppress other, more serious, weeds (see Uses), but there can be little doubt that the dense infestations that can occur under suitable conditions must be competing significantly for nutrients.

Uses

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In Sri Lanka, P. nepalense has been regarded as a valuable ground cover, protecting soil from erosion (Eden and Bond, 1925). Weeding methods were deliberately aimed at encouraging P. nepalense in preference to other more troublesome species. It is not known whether this is still practiced, though in 1951, Haigh commented that P. nepalense was 'a very good cover for tea above 1000 m', only needing to be removed from around the base of bushes.

Uses List

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Environmental

Erosion control or dune stabilization

Similarities to Other Species/Conditions

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Although there are many related Persicaria and Polygonum species occurring as weeds, none are likely to be confused with P. nepalense, due to the latter's distinctive leaf shape. The one exception in Bhutan and perhaps elsewhere in the Himalayas is P. runcinata [ Polygonum runcinatum] which has a similar inflorescence, and sometimes has a somewhat similar leaf shape, but is perennial, with leaves that are normally 'runcinate' with distinct lobes.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control

P. nepalense is shallow-rooted and readily removed by manual or hoe weeding.

Chemical Control

Recent information on the response of P. nepalense to herbicides is sparse. Older reports from Ethiopia show that it is susceptible to many of the standard herbicides for control of broad-leaved weeds, including MCPA, 2,4-D, dicamba, ioxynil, bromoxynil, fluorodifen, ametryne and prometryne (CADU, 1975; Anon., 1978). It is susceptible to terbutryne and methabenzthiazuron post-emergence, but possibly not pre-emergence. It was not controlled by bentazon. It is controlled by full doses of paraquat but may be relatively favoured by the use of reduced doses.

References

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Eden T; Bond TET, 1925. The effect of manurial treatments on the growth of weeds in tea. Empire Journal of Experimental Agriculture, 13:141-157.

Ethiopia; Arssi Rural Development Unit; Crop and Pasture Section, 1978. Report on crop protection surveys and experiments 1976/77. Report on crop protection surveys and experiments 1976/77. P.O. Box 3376, Addis Ababa. Ethiopia, 75 pp.

Ethiopia; Chilalo Agricultural Development Unit, 1975. Crop protection activities, 1974. Parts from report on surveys and experiments carried out in 1974 by Crop and Pasture Section. Crop protection activities, 1974. Parts from report on surveys and experiments carried out in 1974 by Crop and Pasture Section. CADU. Asella Ethiopia, CADU Publication No. 111:147-195

Everaarts AP, 1981. Weeds of vegetables in the highlands of Java. Weeds of vegetables in the highlands of Java. Horticultural Research Institute. Pasarminggu, Jakarta Indonesia, 121 pp.

Gebre H; Tarekegne A; Asmare E, 1987. Preliminary indications on the importance of yield limiting factors on wheat. Fifth Regional Wheat Workshop for Eastern, Central and Southern Africa and the Indian Ocean. Mexico City, Mexico: CIMMYT, 189-193

Grierson AJC; Long DG, 1983. Flora of Bhutan, Volume 1, Part 1. Edinburgh, UK: Royal Botanic Garden.

Guo L, 1993. Ustilago deyeuxiae sp.nov. and three smut species new to China. Mycosystema, 6:51-55

Hafliger TJ; Wolf M, 1988. Dicot Weeds. 1. Basle, Switzerland: CIBA-GEIGY Ltd.

Haigh JC, 1951. A Manual of the Weeds of the Major Crops of Ceylon. Peradenya Manual No. 7. Colombo, Sri Lanka: Department of Agriculture.

Henty EE; Pritchard GH, 1975. Weeds of New Guinea and their Control. Lp, Papua New Guinea: Department of Forests, Division of Botany, Botany Bulletin No.7.

Holm LG; Pancho JV; Herberger JP; Plucknett DL, 1979. A geographical atlas of world weeds. New York, USA: John Wiley and Sons, 391 pp.

Hutchinson J; Dalziel JM; Keay RWJ, 1954. Flora of West Tropical Africa. Volume 1, Part 1, 2nd edition. London, UK: Crown Agents.

Ivens GW, 1967. East African Weeds and their Control. Nairobi, Kenya: Oxford University Press.

Kaul MK, 1986. Weed Flora of Kashmir Valley. Jodhpur, India: Scientific Publishers, 422 pp.

Mena F; Madronero E; Salcedo-Z A; Criollo-E H, 1984. A study of the critical period of competition between weeds and carrot (Daucus carota L.) crops on the Pasto plateau, Narino Department. Revista de Ciencias Agricolas, 8(1/14):114-120

Nimje, 1988. Weed survey of potato fields of the higher hills of Nilgiris. Indian Journal of Weed Science, 20(4):26-31

Numata M; Yoshizawa N, 1975. Weed flora of Japan. Japan Association for the Advancement of Phyto-Regulators. Tokyo, Japan: Zenkoku Noson Kyoiku Kyokai.

Parker C, 1992. Weeds of Bhutan. Weeds of Bhutan., vi + 236 pp.

Reed CF, 1977. Economically important foreign weeds. Potential problems in the United States. Agriculture Handbook No. 498. United States Department of Agriculture. Washington D.C., USA: USDA-ARS.

Stace C, 1991. New Flora of the British Isles. Cambridge, UK: Cambridge University Press.

Stroud A; Parker C, 1989. A Weed Identification Guide for Ethiopia. Rome, Italy: Food and Agriculture Organization.

Tadulingam C; Venkatanarayana G; Mudaliar CR; Sakharam Rao J, 1955. A Handbook of some South Indian Weeds. Second edition. Madras, India: Madras Government Press.

Vibrans H; Hanan Alipi AM, 2008. Notes on neophytes 4. Polygonum nepalense (Polygonaceae), an invasive plant new for Mexico. (Notas sobre neófitas. 4. Polygonum nepalense (Polygonaceae), una planta invasora nueva para México.) Acta Botanica Mexicana, No.82:1-6. http://www.ecologia.edu.mx/publicaciones/ABM.htm

Wang ZR, 1990. Farmland Weeds in China. Beijing, China: Agricultural Publishing House.

Watanabe Y, 1978. Physiological and ecological studies on upland weeds in Hokkaido. Research Bulletin of the Hokkaido National Agricultural Experiment Station, No. 123:17-77

Webb DA; Chater AO; Akeroyd JR, 1993. Polygonum L. In: Tutin TG, Burges NA , Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA, eds. Flora Europaea Volume 1 Psilotaceae to Platanaceae 2nd edition. Cambridge, UK: Cambridge University Press, 91-97.

Wells MJ; Balsinhas AA; Joffe H; Engelbrecht VM; Harding G; Stirton CH, 1986. A catalogue of problem plants in South Africa. Memoirs of the botanical survey of South Africa No 53. Pretoria, South Africa: Botanical Research Institute.

Distribution References

Anon, 1975. Weed flora of Japan (illustrated by colour). In: Weed flora of Japan (illustrated by colour). [ed. by Numata M, Yoshizawa N]. Tokyo, Japan: Japan Association for the Advancement of Phyto-Regulators. 415 pp.

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

Denchev T T, Denchev C M, 2017. Contributions to the smut fungi of Africa. 3. First record of Microbotryum polygoni-alati. Mycobiota. 19-24. DOI:10.12664/mycobiota.2017.07.04

Everaarts A P, 1981. Weeds of vegetables in the highlands of Java. In: Weeds of vegetables in the highlands of Java. Pasarminggu, Jakarta, Indonesia: Horticultural Research Institute. 121 pp.

Grierson A J C, Long D G, 1983. Flora of Bhutan, including a record of plants from Sikkim. Volume 1 parts 1 and 2. Edinburgh, United Kingdom: Royal Botanic Garden. 462pp.

Guo L, 1993. Ustilago deyeuxiae sp.nov. and three smut species new to China. Mycosystema. 51-55.

Hafliger TJ, Wolf M, 1988. Dicot Weeds., 1 Basle, Switzerland: CIBA-GEIGY Ltd.

Haigh J C, 1951. A Manual of the Weeds of the Major Crops of Ceylon. Colombo, Sri Lanka: Department of Agriculture.

Henty E E, Pritchard G H, 1975. Weeds of New Guinea and their control. In: Weeds of New Guinea and their control. Lae, Papua New. Guinea: 180 pp.

Holm L, Pancho J V, Herberger J P, Plucknett D L, 1979. A geographical atlas of world weeds. New York, Chichester (), Brisbane, Toronto, UK: John Wiley and Sons. xlix + 391 pp.

Hutchinson J, Dalziel J M, Keay R W J, 1954. Flora of West Tropical Africa. Volume 1, Part 1. London, UK: Crown Agents.

Hwang KiSeon, Eom MinYong, Park SuHyuk, Won OkJae, Lee InYong, Park KeeWoong, 2015. Occurrence and distribution of weed species on horticulture fields in Chungnam province of Korea. Journal of Ecology and Environment. 38 (3), 353-360. DOI:10.5141/ecoenv.2015.036

Kaul M K, 1986. Weed flora of Kashmir Valley. Jodhpur, India: Scientific Publishers. 422pp.

Mena F, Madroñero E, Salcedo-Z A, Criollo-E H, 1978. A study of the critical period of competition between weeds and carrot (Daucus carota L.) crops on the Pasto plateau, Nariño Department. (Estudio del período crítico de la competencia entre malezas y el cultivo de la zanahoria (Daucus carota L.) en el altiplano de Pasto, Departamento de Nariño.). Revista de Ciencias Agricolas. 8 (1/14), 114-120.

Nimje, 1988. Weed survey of potato fields of the higher hills of Nilgiris. Indian Journal of Weed Science. 20 (4), 26-31.

Parker C, 1992. Weeds of Bhutan. Thimphu, Bhutan: National Plant Protection Centre. vi + 236 pp.

Reed C F, 1977. Economically important foreign weeds. Potential problems in the United States. Washington, D.C. USA: United States Department of Agriculture. 746 pp.

Stace C, 1991. New Flora of the British Isles. Cambridge, UK: Cambridge University Press.

Stroud A, Parker C, 1989. A weed identification guide for Ethiopia. In: A weed identification guide for Ethiopia. Rome, Italy: Food and Agriculture Organization. 278 pp.

Tadulingam C, Venkatanarayana G, Mudaliar C R, Sakharam Rao J, 1955. A handbook of some South Indian weeds. Madras, India: Madras Government Press.

Vibrans H, Hanan Alipi A M, 2008. Notes on neophytes 4. Polygonum nepalense (Polygonaceae), an invasive plant new for Mexico. (Notas sobre neófitas. 4. Polygonum nepalense (Polygonaceae), una planta invasora nueva para México.). Acta Botanica Mexicana. 1-6.

Webb DA, Chater AO, Akeroyd JR, 1993. (Polygonum L). In: Flora Europaea Psilotaceae to Platanaceae, 1 (2nd) [ed. by Tutin TG, Burges NA, Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA]. Cambridge, UK: Cambridge University Press. 91-97.

Wells M J, Balsinhas A A, Joffe H, Engelbrecht V M, Harding G, Stirton C H, 1986. A catalogue of problem plants in southern Africa incorporating the national weed list of South Africa. Memoirs, Botanical Survey of South Africa. v + 658pp.

Wibowo T, Iskandar E A P, 2013. Broadleaved weeds in turf grass blocks of Cibodas Botanic Garden, Cianjur, Indonesia [Conference poster]. In: The role of weed science in supporting food security by 2020. Proceedings of the 24th Asian-Pacific Weed Science Society Conference, Bandung, Indonesia, October 22-25, 2013 [The role of weed science in supporting food security by 2020. Proceedings of the 24th Asian-Pacific Weed Science Society Conference, Bandung, Indonesia, October 22-25, 2013.], [ed. by Bakar B H, Kurniadie D, Tjitrosoedirdjo S]. Bandung, Indonesia: Weed Science Society of Indonesia. 578-582.

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Polygonum nepalense (Nepal persicaria)

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