Know your alien invasive plant: Kariba weed
Hillcrest Conservancy will produce weekly articles regarding the various alien invasive plant species in the Highway area to help the community identify and eliminate them.
THIS week, Hillcrest Conservancy, takes a look at the Kariba weed, as part of its series of articles on alien invasive plants, to help the community to identify and eradicate them from their gardens.
The Kariba weed’s scientific name is Salvinia molesta (Salviniaceae) but it is also known as the Salvinia, African pyle, water fern, or watervaring (in Afrikaans).
Description: It is an aquatic, mat-forming, free-floating fern with horizontal stems up to 25cm long. Green to yellow-green oval leaves form in pairs with dense upper surface cover of hairs. Feathery, root-like leaves hang down in the water. This species is probably one of the best known alien species as it rose to notoriety when it first occurred in the Kariba dam in Zimbabwe.
Where does this species come from? Brazil in South America
What is its invasive status in South Africa? Category 1b and as it spreads so readily it may not be kept in any garden as it can grow into a mass in a very short time from a single leaf.
Where in South Africa is it a problem? Western and Eastern Cape, KwaZulu-Natal, Gauteng, Mpumalanga and Limpopo.
How does it spread? Spreads only vegetatively by fragmentation.
Why is it a problem? Forms dense mats up to 50cm thick which completely cover a water surface. The mats clog waterways and irrigation equipment, reduce waterflow, impede navigation, fishing and other recreational activities, provide a breeding place for mosquitoes and bilharzia-carrying snails. Dense mats reduce light penetration, reduce oxygen levels and result in poor water quality. Dense mats threaten indigenous aquatic plant and animal life
Does the plant have any uses? Ornament.
Contact Ian Pattrick on 079 909 5458 or Hillcrest Conservancy chairman, George Victor, on 073 901 3902 or e-mail georgevic@telkomsa.net
