Click on images to enlarge
red flower (Photo: Derek Ramsey CC BY-SA)
mature plants (Photo: Derek Ramsey CC BY-SA)
orange flower head Photo: (Kurt Stüber, CC BY-SA)
foliage (Photo: Derek Ramsey CC BY-SA)
Tithonia rotundifolia (Mill.) S.F. Blake
Helianthus speciosus Hook.; Tagetes rotundifolius Mill.; Tithonia speciosa (Hook.) Griseb.
Red sunflower, giant Mexican sunflower, Japanese sunflower, Mexican sunflower, shrub sunflower, tree marigold
Asteraceae (Compositae)
Central America
Locations within which Tithonia diversifolia is naturalised include Australia, south-eastern USA and many islands in the Pacific Ocean.
Tithonia rotundifolia is naturalised in parts of Kenya and Uganda (A.B.R. Witt pers. obs.) and in Tanzania (Tropical Biology Association 2010). In Kenya, and Tanzania, this species has been found at an altitudinal range of 1500-1700 m.
This species invades savanna grasslands, roadsides, degraded land and riparian zones (banks of watercourses).
Tithonia rotundifolia is a much branched, bushy herb to 1.5-2 or 3 m in height.
The stem is weak in the mid-section, but slightly woody at the base. The stems are slightly ridged (striate) and hairy (pubescent) when young.
The alternately arranged leaves are borne on stalks (petioles) 2-10 cm long. The leaf blades (6-33 cm long and 5-22 cm wide) have tapered (cuneate) bases and 3-7 pointed lobes with scalloped (crenate) or toothed (serrate) margins. These leaves are finely hairy (puberulent) and greyish-green in colour. When the leaf dries, it is quite brittle.
T. rotundifolia has a round (capitate) flower-head, to 90 mm across, bright orange-red. The flower-heads are terminal on main and side branches, solitary on long stalks, much swollen and velvety below the heads. Flower buds are pointed. The bracts are lanceolate (narrow pointed) and in two series.
The fruits are brown achenes, in a round spiky mass that is brown in colour.
This species reproduces by seed. It can also propagate vegetatively from basal stems. The seeds may be dispersed by animals, water and in clothing, They may also be spread in dumped garden waste and contaminated agricultural produce. Seeds can be dormant for up to four months.
Another introduced species of Tithonia, Tithonia diversifolia (Mexican sunflower), can be confused with T. rotundifolia especially before it flowers. T. diversifolia can grow to a similar size in similar habitats but its leaves have five lobes. The flowers are similar in shape, slightly larger and bright yellow in colour. Exceptionally, T. rotundifolia has yellow flowers similar to T. diversifolia.
Tithonia rotundifolia is planted as an ornamental and is also grown as a green manure. However, these uses cannot compensate for this plant's overall negative impacts.
Tithonia rotundifolia is a competitive weed and reported to be allelopathic. It can compete with crop plants and shade out native vegetation.
T. rotundifolia has been listed as a noxious weed in South Africa (prohibited plants that must be controlled. They serve no economic purpose and possess characteristics that are harmful to humans, animals or the environment).
The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are introduced below.
The best form of invasive species management is prevention. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.
Young plants can be removed by hand for seedlings and saplings. It is difficult to remove larger plants by hand as they coppice readily. Various herbicides can be sprayed onto Tithonia rotundifolia for effective control. When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.
The editors do not know of any biological control programmes targeted at this species.
Henderson, L. (2001). Alien weeds and invasive plants. A complete guide to declared weeds and invaders in South Africa. Plant Protection Research Institute Handbook No. 12, 300pp. PPR, ARC South Africa.
Tropical Biology Association (2010). Usambara Invasive Plants - Amani Nature Reserve - www.tropical-biology.org/research/dip/species.htm.
Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.
This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).
BioNET-EAFRINET Regional Coordinator: [email protected]