Euston-Brown, D., Rathogwa, N & Richardson ... - DWA Home Page

expected. It grows especially well on nutrient rich clay soils that are moist for longer periods or
perennially (e.g. riparian habitats and on the edges of irrigated sugar cane plantations). However, it
was also seen on deep sandy soils in the lowlands, but tends to die back after droughts in this habitat.
Chromolaena has many attributes that add to its invasiveness. Following Sharma et al.’s (2005) scheme
for lantana, chromolaena has:
1) Phenotypic plasticity – it has adapted to growing in a wide range of habitats but the south African
biotype is fairly uniform, and does not have the problem of different varieties like lantana, at least
in South Africa.
2) Interaction with animals – the destructive foraging activities of vertebrates benefits chromolaena by
creating appropriate establishment sites in the soil. However, browsing does not appear to enhance
vegetation reproduction. Heavy browsing could help to limit flowering.
3) Geographical range – the wide range of habitats that chromolaena is able to spread into is more
limited than for lantana. However the cool and dry adapted biotype is still spreading and the
occurrence of dense infestations is increasing.
4) Vegetative reproduction – individuals can spread vegetatively by horizontal stems producing roots
when they come into contact with the soil. This was only observed at one site in Swaziland, and
vegetative reproduction in chromolaena can be regarded as poorly developed.
5) Fire tolerance – the plants burn readily but only when dry after cutting or drought. It does not
resprout readily like lantana. However, germination and establishment is also enhanced in the
post fire environment. Extremely hot fires (>100 degrees Celsius) can kill the seeds (Mbalo &
Witkowski, 1997)
6) Competitive ability – once established chromolaena tends to persist and blocks the natural
succession by out competing the indigenous plants. However, numerous indigenous woody plant
seedlings are able to persist under chromolaena, and if thinned or cleared many of these could
then grow into the canopy (unless they are burnt while still young).
7) Allelopathy – although the oils in chromolaena leaves could be allelopathic this has not been
demonstrated yet. Many indigenous woody plant seedlings and young plant are able to persist
under chromolaena, but unless the chromolaena thicket is disturbed or cleared, these are
shaded out.
Chromolaena odorata
Development of a clearing protocol based on ecological criteria for Mesic Savannas and Sweet Grassveld for the Working for Water Programme
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