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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Environmental Programmes

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Dense water weed

Egeria densa

Common name:

Dense water weed

Scientific name:

Egeria densa (Hydrocharitaceae)

Alternative common names:

Waterpes (Afrikaans)

A submerged aquatic plant with slender stems up to 3m long. Green, finely serrated leaves 15-30mm long in whorls of 4-5, sometimes 3-8. Yellow or cream flowers appear on long stalks about 20mm above the water surface. This aquatic plant invades still or slow-moving water in lakes and ponds.

Additional Info

  • Where does this species come from?

    South America (Argentina, south-eastern Brazil and Uruguay)

    What is its invasive status in South Africa?

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

    Where in South Africa is it a problem?

    KwaZulu-Natal and the Western Cape.

    How does it spread?

    Spreads by fragmentation of the plant parts and dormant tubers.

    Why is it a problem?

    This aquatic invasive plant can negatively impact an aquatic ecosystem. It displaces native plants, blocks light needed for photosynthesis, reduces the amount of dissolved oxygen in the water and deposits silt and organic matter several times the normal rate.

    What does it look like?

    General description: Submerged aquatic plant with slender stems up to 3m long. Leaves: Green; margins finely serrated, but serrations not visible with the naked eye, leaf tip ends in one spine cell. Flowers: Yellow or cream, three-petalled; flowers about 15mm across, long-stalked and protrudes 20mm above the water surface.

    Does the plant have any uses?

    Used as an ornamental and for aquarium trade.

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General News Updates

2019 National Symposium on Biological Invasio…


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


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


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Permits for planting indigenous Cynodon?


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


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


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