Ornamental plants as invasive aliens in Kruger National Park, South Africa
Kruger National Park (KNP) covers an area of 20;000 km² in the Northeast corner of South Africa. It extends 360 km north to south, and 90 km east at its widest point. The KNP maintains about 885 km of paved road, 1700 km of gravel roads open to tourists, and 737 km of gravel roads for park management. There are 5 large tourist camps, and about 36 smaller camps and ranger outposts. The villages and camps in the KNP are all landscaped to varying degrees. Until recently, landscaping typically involved the use of many alien species. As was the case elsewhere in South Africa, despite the rich local flora, alien plant species were often favoured over indigenous species for ornamental use. Three factors play a role in the spread of these introduced plants: the large number of mammalian and avian seed dispersers; the proximity of the tourist camps and staff villages to the rivers; and the fact that the camps are evenly distributed across the entire KNP landscape.
Management of ornamental alien plants started in the Skukuza village in the mid 1980s. This initiative was not well supported by the staff, and resulted in continuous resistance from residents towards the alien plant control team. As a result, less effort was placed on preventative control measures in the village and work continued on alien plant species that had already escaped into the surrounding areas (mainly Opuntia stricta and Lantana camara). From the early 1980s until the mid 1990s, the alien plant control team focused on about 30 well known alien plants, and allowed the use of numerous other potential invasive species to continue, for example Wedelia trilobata and Alpinia zerumbet. Following the 1999 survey of alien plants in the villages, KNP management approved a new policy, and a substantial program was launched to remove the alien species.
The species recorded as invasive in the KNP are listed below. Each species has been checked against the Global Compendium of Weeds (GCW) in order to indicate its invasive behaviour elsewhere in the world, as well as in DAISIE and EPPO databases to determine its occurrence and invasiveness within the EPPO region. This later information remains only indicative, and “/” indicates that no further information could be found.
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Species
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Origin
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Cult.
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GCW*
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EPPO region
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Agave sisalana (Agavaceae)
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Neotrop.
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Yes
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W, NW, AW, EW
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ES, IT
|
|
Ageratum conyzoides (Asteraceae)
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Mexico
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Yes
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W, NW, AW, EW
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PT (incl. Madeira)
|
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Ageratum houstonianum (Asteraceae)
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N-Am.
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Yes
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W, NW, AW, EW
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ES, PT (incl. Madeira), casual in many countries
|
|
Amaranthus spinosus (Polygonaceae)
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Trop. Am.
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No
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W, AW, EW
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ES, IT, PT (incl. Madeira)
|
|
Antigonon leptopus (Polygonaceae)
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N ; S-Am.
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Yes
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W, SW, AW, EW
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PT (incl. Madeira)
|
|
Argemone mexicana (Papaveraceae)
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N ; S-Am.
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No
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W, SW, AW, EW
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ES
|
|
Argemone subfusiformis (Papaveraceae)
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S-Am.
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No
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W, NW, AW, EW
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/
|
|
Aristolochia elegans (Aristolochiaceae)
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S-Am.
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Yes
|
W, NW, SW, AW, EW
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/
|
|
Arundo donax
(Poaceae)
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W-As.
|
Yes
|
W, NW, AW, EW
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Widely distributed
|
|
Asclepias curassavica (= A. syriaca) (Asclepiadaceae)
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N-Am.
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Yes
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W, NW, AW, EW
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Widely distributed
|
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Bidens pilosa
(Asteraceae)
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N ; S-Am.
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No
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W, AW, EW
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CY, ES (incl. Islas Canarias), FR, IT, PT (incl. Azores, Madeira),
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Caesalpinia decapetala (= C. sepiaria) (Caesalpiniaceae)
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As.
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No
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W, NW, AW, EW
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/
|
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Callisia repens (Commelinaceae)
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N ; S-Am.
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Yes
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W
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/
|
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Cannabis sativa
(Cannabaceae)
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Asia
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No
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W, NW, AW, EW
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Widely distributed
|
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Cardiospermum grandiflorum (Sapindaceae)
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Af. N ; S-Am.
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Yes
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W, NW, AW, EW
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IT, PT (incl. Madeira)
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Cardiospermum halicacabum ;(Sapindaceae)
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Af., As., N ; S-Am.
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Yes
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W, NW, AW, EW
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ES, FR, GR
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Cassia bicapsularis
(Fabaceae)
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Caribbean
|
?
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W, AW, EW
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PT (incl. Madeira)
|
|
Cassia didymobotrya (Fabaceae)
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Af.
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Yes
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W, AW, EW
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PT (incl. Madeira)
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Cassia occidentalis
(Fabaceae)
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S-Am.
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?
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W, NW, AW, EW
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/
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Cassia floribunda
(Fabaceae)
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N-Am.
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?
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W, AW, EW
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PT (incl. Madeira)
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Eupatorium odoratum
(= Chromolaena odorata) (Asteraceae)
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N ; S-Am.
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No
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W, NW, AW, EW
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/
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Datura ferox
(Solanaceae)
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China
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No
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W, NW, AW, EW
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ES (incl. Baleares), FR, IT
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Datura innoxia
(Solanaceae)
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N ; S-Am.
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No
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W, NW, AW, EW
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CY, ES (incl. Baleares, Islas Canarias), FR (Corse), HR, IT (Sardinia), PT (Madeira), TR
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Datura stramonium (Solanaceae)
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N-Am.
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No
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W, NW, AW, EW
|
|
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Flaveria bidentis
(Asteraceae)
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S-Am.
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No
|
W, AW, EW
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/
|
|
Ipomoea alba (= Calonyction aculeatum) (Convolvulaceae)
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N ; S-Am.
|
Yes
|
W, SW, NW, AW, EW
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/
|
|
Kalanchoe daigremontiana (Crassulaceae)
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Madagascar
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Yes
|
W
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ES (incl. Baleares), PT (incl. Madeira)
|
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Kalanchoe tubiflora (Crassulaceae)
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Madagascar
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Yes
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W
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IT, PT (incl. Madeira)
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Lantana camara
(Verbenaceae)
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S-Am.
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Yes
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W, NW, AW, EW
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ES (incl. Baleares, Islas Canarias), FR (incl. Corse), IL, IT, PT (incl. Azores, Madeira)
|
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Melia azedarach
(Meliaceae)
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As., Australas.
|
Yes
|
W, NW, SW, AW, EW
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CY, ES (incl. Baleares), FR, IL, IT, MT, PT (incl. Madeira)
|
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Mimosa pigra
(Fabaceae)
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Af., N ; S-Am.
|
?
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W, NW, AW, EW
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/
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Myriophyllum aquaticum (Haloragaceae) (EPPO List of IAP)
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S-Am.
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Yes
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W, NW, AW, EW
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Widely distributed
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Nerium oleander (Apocynaceae)
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Euras, Af.
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Yes
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W, NW, AW, EW
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Indigenous - Widely distributed
|
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Opuntia stricta
(Cactaceae)
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N ; S-Am.
|
Yes
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W, NW, AW, EW
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Medit. area.
|
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Parthenium hysterophorus (Asteraceae)
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C ; S-Am.
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No
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W, NW, AW, EW
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/
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Passiflora edulis
(Passifloraceae)
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S-Am.
|
Yes
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W, NW, AW, EW
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PT (incl. Azores, Madeira)
|
|
Pistia stratiotes (Araceae) (EPPO Alert List)
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S-Am.
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Yes
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W, SW, NW, AW, EW
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ES (incl. Islas Canarias), PT, SI
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|
Pontederia cordata (Pontederiaceae)
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N ; S-Am.
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Yes
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W, NW, AW, EW
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ES, FR, GB, IE, IT, NL
|
|
Psidium guajava
(Myrtaceae)
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N ; S-Am.
|
Yes
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W, SW, NW, AW, EW
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ES (incl. Islas Canarias), PT (incl. Madeira)
|
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Ricinus communis (Euphorbiaceae)
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Af.
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No
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W, NW, AW, EW
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Widely distributed
|
|
Sesbania bispinosa
(Fabaceae)
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Af., As.
|
No
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W, AW
|
/
|
|
Sesbania punicea
(Fabaceae)
|
S-Am.
|
Yes
|
W, SW, NW, AW, EW
|
PT (incl. Madeira)
|
|
Solanum seaforthianum (Solanaceae)
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N ; S-Am.
|
Yes
|
W, NW, AW, EW
|
/
|
|
Tagetes minuta
(Asteraceae)
|
S-Am.
|
No
|
W, NW, AW, EW
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CY, ES, FR (incl. Corse), GR, HR, IT, TR
|
|
Tecoma stans
(Bignoniaceae)
|
N ; S-Am.
|
Yes
|
W, SW, NW, AW, EW
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PT (incl. Madeira)
|
|
Thevetia peruviana (Apocynaceae)
|
Peru
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Yes
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W, NW, EW
|
/
|
|
Tithonia diversifolia (Asteraceae)
|
C-Am.
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Yes
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W, NW, AW, EW
|
/
|
|
Verbena bonariensis (Verbanaceae)
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S-Am.
|
?
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W, AW, EW
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FR, IT, PT (incl. Azores, Madeira)
|
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Verbena brasiliensis (Verbanaceae)
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S-Am.
|
?
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W, EW
|
/
|
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Wedelia trilobata
(Asteraceae)
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N ; S-Am.
|
Yes
|
W, SW, NW, AW, EW
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/
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* Abbreviations for the Global Compendium of Weeds column:
W: weed; SW: sleeper weed; NW: noxious weed; AW: Agricultural Weed; EW: Environmental Weed.
Of particular interest are species which are invasive in the KNP and elsewhere in the world according to the Global Compendium of Weeds, and that are not recorded in the EPPO region, or which have a very limited distribution.
Among these species, some were used as ornamental plants in the KNP: Aristolochia elegans, Ipomoea alba, Sesbania punicea, Solanum seaforthianum, Wedelia trilobata.
Others were not known to be used as ornamentals: Argemone subfusiformis, Caesalpinia decapetala, Cassia occidentalis, Eupatorium odoratum, Parthenium hysterophorus.
Sources
Foxcroft L, Richardson D (2008) Ornamental plants as invasive plants: problems and solutions in Kruger National Parl, South Africa. Environmental management 41, 32-51.