Wolffia arrhiza 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Alismatales Araceae

Scientific Name: Wolffia arrhiza (L.) Horkel ex Wimm.
Regional Assessments:
Common Name(s):
English Rootless Duckweed
French Wolffia sans Racines, Wollfie
Lemna arrhiza L.
Wolffia michelii Schleid.
Taxonomic Notes: According to Royal Botanic Gardens, Kew WCSPF (World Checklist of Selected Plant Families), this genus belongs to the Araceae Family.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2017
Date Assessed: 2016-06-12
Assessor(s): Gupta, A.K. & Beentje, H.J.
Reviewer(s): Luke, W.R.Q.
Contributor(s): Lansdown, R.V.
Facilitator/Compiler(s): Maiz-Tome, L.

This species covers a wide geographic range and it is known from many sites. No significant threats have been reported.

Previously published Red List assessments:

Geographic Range [top]

Range Description:

The main distribution centre for W. arrhiza is in Europe, with populations scattered throughout Africa south of the Sahara, as well as a few populations in North Africa and Asia. It is also known from one locality near Rio de Janeiro, Brazil (Landolt 1986) where it has been introduced.

Countries occurrence:
Albania; Algeria; Angola; Austria; Belarus; Belgium; Benin; Bhutan; Bosnia and Herzegovina; Botswana; Brazil (Rio de Janeiro); Bulgaria; Burundi; Congo, The Democratic Republic of the; Côte d'Ivoire; Croatia; Czech Republic; France; Germany; Ghana; Guinea-Bissau; Hungary; India (Jammu-Kashmir); Iran, Islamic Republic of; Italy (Italy (mainland), Sicilia); Kenya; Lebanon; Liechtenstein; Luxembourg; Macedonia, the former Yugoslav Republic of; Madagascar; Malawi; Moldova; Montenegro; Morocco; Mozambique; Netherlands; Nigeria; Palestinian Territory, Occupied; Philippines; Poland; Portugal; Russian Federation (Central European Russia, East European Russia, European Russia); Rwanda; Senegal; Serbia; Slovenia; South Africa (Eastern Cape Province, Free State, KwaZulu-Natal, Limpopo Province, Northern Cape Province, Western Cape); Spain; Syrian Arab Republic; Taiwan, Province of China (Taiwan, Province of China (main island)); Tanzania, United Republic of; Togo; Uganda; Ukraine; United Kingdom (Great Britain)
Additional data:
Lower elevation limit (metres):1
Upper elevation limit (metres):2100
Range Map:Click here to open the map viewer and explore range.

Population [top]


This species naturally undergoes massive population fluctuations and when it occurs at low abundance it is extremely easy to overlook. There is no information on global population trends. In Europe populations seem to be stable. It can form large populations in suitable habitats.

Current Population Trend:Stable
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:

W. arrhiza typically occurs in base-rich lowland ditches and ponds (Preston and Croft 1997) in mesotrophic to eutrophic water. It sometimes occurs with Wolfiella and Lemna minor, or with Pistia; it can be abundant enough to form a scum. 

Continuing decline in area, extent and/or quality of habitat:No

Use and Trade [top]

Use and Trade: Where it grows with Pistia in Africa it is sometimes collected and used as a manure.

Threats [top]

Major Threat(s):

There are no known past, ongoing, or future threats to this species.

Conservation Actions [top]

Conservation Actions:

There are no conservation measures in place nor likely to be needed.

Classifications [top]

5. Wetlands (inland) -> 5.5. Wetlands (inland) - Permanent Freshwater Lakes (over 8ha)
suitability:Suitable  major importance:Yes
5. Wetlands (inland) -> 5.6. Wetlands (inland) - Seasonal/Intermittent Freshwater Lakes (over 8ha)
5. Wetlands (inland) -> 5.7. Wetlands (inland) - Permanent Freshwater Marshes/Pools (under 8ha)
suitability:Suitable  major importance:Yes
5. Wetlands (inland) -> 5.8. Wetlands (inland) - Seasonal/Intermittent Freshwater Marshes/Pools (under 8ha)
5. Wetlands (inland) -> 5.13. Wetlands (inland) - Permanent Inland Deltas
15. Artificial/Aquatic & Marine -> 15.9. Artificial/Aquatic - Canals and Drainage Channels, Ditches
suitability:Suitable  major importance:Yes

In-Place Research, Monitoring and Planning
  Action Recovery plan:No
  Systematic monitoring scheme:No
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over part of range
  Occur in at least one PA:No
  Area based regional management plan:No
  Invasive species control or prevention:No
In-Place Species Management
  Harvest management plan:No
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:No
In-Place Education
  Subject to recent education and awareness programmes:No
  Included in international legislation:No
  Subject to any international management/trade controls:No

Bibliography [top]

African Plants Database (version 3.4.0). 2015. Conservatoire et Jardin botaniques de la Villle de Genève and South African National Biodiversity Institute, Pretoria. Available at: (Accessed: November 2015).

Cook, C.D.K. 2004. Aquatic and wetland plants of southern Africa. Backhuys Publishers, Leiden, The Netherlands.

eMonocot. 2016. eMonocot. An online resource for monocot plants. Available at:

Hepper F.N. 1973. Flora of tropical East Africa: Lemnaceae. Crown Agents, London.

IUCN. 2017. The IUCN Red List of Threatened Species. Version 2017-1. Available at: (Accessed: 27 April 2017).

Landolt, E. 1986. Biosystematic investigation in the family of duckweeds (Lemnaceae), 2. The family of Lemnaceae - a monographic study. Veröffentlichungen des Geobotanischen Instituts der Eidgenössischen Technischen Hochschule, Zürich.

Symoens J.J. 1997. Hydrocharitaceae. In: Edwards, Sebsebe & Hedberg (ed.), Flora of Ethiopia and Eritrea, Addis Ababa. Available at: (Accessed: 08 Apr 2015).

USDA. 2010. Germplasm Resources Information Network - (GRIN) [Online Database]. National Germplasm Resources Laboratory, Beltsville, Maryland. Available at:

WCSPF. 2010. World Checklist of Selected Plant Families. Available at:

Citation: Gupta, A.K. & Beentje, H.J. 2017. Wolffia arrhiza. The IUCN Red List of Threatened Species 2017: e.T164241A84301916. . Downloaded on 18 September 2018.
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