German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Water lettuce

Pistia stratiotes

Common name:

Water lettuce

Scientific name:

Pistia stratiotes (Araceae)

Alternative common names:

Nile cabbage, Nile lettuce, shell flower, water cabbage, water fern (English), Waterslaai (Afrikaans)

A free-floating, aquatic perennial plant seldom exceeding 150-200mm in diameter. The plants consist of a rosette of leaves and a tuft of long, fibrous roots beneath and it resembles floating lettuces. The leaves are pale yellow-green, narrower at the base and round, straight or notched at their tips, ribbed, with many longitudinal veins radiating from the base. The leaves are softly hairy on both surfaces. Small pale green or white flowers appear from February-May, but occasionally throughout the year in warm tropical climates and it produces small, green capsules. The leaves are poisonous and known to cause intense internal irritation. It invades dams, pans and slow-moving rivers in subtropical regions.

Additional Info

  • Where does this species come from?

    South America (Brazil)

    What is its invasive status in South Africa?

    Existing legislation: CARA 2002 – Category 1 NEMBA – Category 1b

    Where in South Africa is it a problem?

    KwaZulu-Natal, Eastern Cape and Mpumalanga

    How does it spread?

    Spreads and reproduces by seeds and rhizomes

    Why is it a problem?

    Forms dense mats which completely cover a water surface. The mats clog waterways and irrigation equipment, reduce waterflow, impede navigation, fishing and other recreational activities, provides a breeding place for mosquitoes and bilharzia-carrying snails

    What does it look like?

    General description: A free-floating, aquatic perennial plant seldom exceeding 150-200mm in diameter. The plants consist of a rosette of leaves and a tuft of long, fibrous roots beneath and resemble floating lettuces. Leaves: Pale yellow-green, narrower at the base and round, straight or notched at their tips, ribbed, with many longitudinal veins radiating from the base. The leaves are softly hairy on both surfaces. Flowers: Small pale green or white flowers appearing from February-May, but occasionally throughout the year in warm tropical climates. Fruit/Seeds: Produces small, green capsules

    Does the plant have any uses?

    Used as an aquatic ornament

    Plant me instead alternatives

    Small yellow waterlily (Nymphoides thunbergiana), Cape pond weed (Aponogeton distachyos)

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General News Updates

2019 National Symposium on Biological Invasio…

26-02-2019

This is your invitation to South Africa's 2019 National Symposium on Biological Invasions. The convention is hosted by the Centre for Invasion Biology (CIB), University of Stellenbosch, and the Biolo... Read more

2019 Invasive Species Training

22-01-2019

During the past five years (2014-2018), ISSA invasive species trainers have trained 4 000 in the identification of invasive species and laws pertaining to invasive species across South Africa.  ... Read more

Alien Grass Working Group

04-09-2018

Who are we? The South African National Alien Grass Working Group was jointly initiated by the South African Biodiversity Institute (SANBI) and the Centre for Excellence in Invasion Biology (C·I·B) in... Read more

Permits for planting indigenous Cynodon?

01-03-2018

On 16 February, 2018, South Africa's Department of Environmental Affairs issued amendments to the regulations and lists relating to the National List of Invasive Species.  Updates to the draft&n... Read more

Invasive species training 2018 dates released

28-02-2018

Interested in invasive species?  How much do you know about NEMBA invasive species compliance for landowners and organs of state? The South African Green Industries Council (SAGIC) have released... Read more

Communications post for Africa advertised

25-01-2018

The Nature Conservancy has advertised a brand new post:  Communications Manager, Africa Region. Knowledge of invasive species and water would be an asset in this post. See details below:    Job Titl... Read more