Chromolaena odorata (L.) R.M. King & H. Rob.

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Chromolaena odorata

Photo: Costas Zachariades

Chromolaena odorata

Photo: Costas Zachariades

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Synonyms: Eupatorium conyzoides Vahl
Eupatorium odoratum L.
Common names: Paraffienbos (Afrikaans) Siam weed (English) Triffid weed (English)
Frequency: Very rare casual
Status: Introduced
Scrambling or climbing shrub, to 4 m (or more when supported). Leaves ovate to triangular, 3-veined from the base, gland-dotted below, smelling strongly of turpentine or paraffin when crushed. Capitula c. 10 × 3 mm, cylindric. Achenes c.5 mm, straw-coloured.
Notes: Cultivated for ornament and now an aggressive weed in many moist, tropical areas of the world; e.g. in S Africa in Mpumalanga and KwaZulu-Natal.

This species appears to be a rare casual in Zimbabwe, having been recorded once in Zimbabwe near Chinhoyi in 1967.

There are two biotypes which differ on flower colour: the S African one has white flowers and the W African one pale blue. The Zimbabwe specimen is of the W African type (Zachariades, in litt.).

The species is somewhat similar to the Crofton weed (Ageratina adenophora), which also has white flowers in corymbose heads. However, these can be separated as follows: C. odorata is a true climbing shrub whereas A. adenophora is a herb, although it may attain 1.5 metres. C. odorata does not have the glandular and purple stems and leaves which A. adenophora has.

We are very grateful to Dr Costas Zachariades for informing us of the record, which was published in (Gautier, 1992), for providing us with the photographs of the herbarium material and other information about this species.

As far as I am aware, C. odorata is not a weed in the Chinhoyi area. Perhaps the climate was not suitable. McFadyen & Skarratt (1996) (see above) published the results of a climatic matching model which indicated that the eastern parts of Zimbabwe and adjoining part of Mozambique are highly suitable climatically for C. odorata. It is in these warm moist areas that we may expect eventually to find Chromolaena.

Another interesting observation is that the altitude of Chinhoyi is c.1200m and the hills around it do not seem to attain 1600m; perhaps there is an error here.
Derivation of specific name: odorata: odorous, fragrant
Altitude range: (metres)
Flowering time:
Worldwide distribution: North, Central and South America (SE USA to N Argentina)
Zimbabwe distribution: N
Growth form(s):
Endemic status:
Red data list status:
Insects associated with this species:
Spot characters: Display spot characters for this species

Gautier, L. (1992). Taxonomy and distribution of a tropical weed: Chromolaena odorata (L.) R. King and H. Robinson Candollea 47

McFadyen, R. & Skarratt, B. (1996). Potential distribution of Chromolaena odorata (Siam Weed) in Australia, Africa, and Oceania. Agriculture, Ecosystems and Environment 59


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Other sources of information about Chromolaena odorata:

External websites:

Biodiversity Explorer (Biodiversity of southern Africa): Chromolaena odorata
EOL (Encyclopedia of Life): Chromolaena odorata
ePIC (electronic Plant Information Center): Chromolaena odorata
Flora Zambesiaca web site: Chromolaena odorata
Google: Web - Images - Scholar
GRIN (Germplasm Resources Information Network) taxonomy for plants report for Chromolaena odorata
IPNI (International Plant Names Index): Chromolaena odorata
Ispot Southern Africa : Chromolaena odorata
JSTOR Plant Science: Chromolaena odorata
Kew Herbarium catalogue: Chromolaena odorata
Tropicos: Chromolaena odorata
West African Plants database: Chromolaena odorata

Copyright: Mark Hyde, Bart Wursten, Petra Ballings and Meg Coates Palgrave, 2002-16

Hyde, M.A., Wursten, B.T., Ballings, P. & Coates Palgrave, M. (2016). Flora of Zimbabwe: Species information: Chromolaena odorata., retrieved 31 May 2016

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