Scientific name

Tithonia diversifolia A. Gray

Synonyms

Mirasolia diversifoliaHemsl.

Common names

Mexican sunflower, tree marigold, Mexican tournesol, Nitobe chrysanthemum

Family

Asteraceae (Compositae)

Origin

Native to Mexico and Central America

Naturalised distribution (global)

Locations within which Tithonia diversifolia is naturalised include Australia, south-eastern USA, tropical and subtropical African and many oceanic islands with warm climates.

Introduced, naturalised or invasive in East Africa

Tithonia diversifolia is invasive in parts of Kenya, Uganda (A.B.R. Witt pers. obs.) and Tanzania (Tropical Biology Association 2010).

Habitat

Naturalised along roadsides and other disturbed areas (ICRAF 1997). It is abundant in East Africa and is spreading rapidly in habitats such as grasslands, disturbed land and riparian zones (banks of watercourses).

Description

Tithonia diversifolia is a robust long-lived (perennial)  herbaceous and bushy plant that grows up to 3 m tall.

The stems are hollow, 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.

The large daisy-like flower-heads (capitula) are borne in small groups at the ends of the leafy branches, on stalks (peduncles) 7-30 cm long. These flower-heads (5-15 cm wide) look like sunflowers, but have yellow centres (3-5 cm across). They have 7-15 bright yellow 'petals' (ray florets) that are 4-7 cm long and 9-16 mm wide, each with three small teeth at their tips. There are also numerous (80-120) tiny yellow flowers (tubular florets) in the centre of the flower-heads and they are surrounded by several rows of green bracts (an involucre). Flowering occurs  mainly during the rainy seasons in East Africa.

The 'seeds' (achenes) are 4-8 mm long and topped with a ring (pappus) of scales and two awns (about 5 mm long). These 'seeds' are covered in close-lying hairs (they are appressed pubescent), blackish in colour, and are somewhat four-angled.

Reproduction and dispersal

Tithonia diversifolia is a prolific seeder which retains its seeds until the plant dries in the dry season when the seeds disperse and are spread by wind, water and the movement of people, livestock and vehicles.

Similar species

Another introduced species of Tithonia, T. rotundifolia (red sunflower) can be confused with Tithonia diversifolia especially before it flowers.  T. rotundifolia can grow to a similar size in similar habitats but has leaves without lobes or a maximum of three lobes.  The flowers are similar in shape, slightly smaller and bright orange or red in colour.  Exceptionally, it has yellow flowers similar to T. diversifolia.

Economic and other uses

Tithonia diversifolia is a fast-growing species, used as a garden ornamental, a green manure in agroforestry systems, a live fence (hedge) and as a fodder crop for livestock such as goats and cattle. However, these uses cannot compensate for this plant's overall negative impacts.

Environmental and other impacts

Tithonia diversifolia can quickly colonise disturbed areas. It can also establish itself as a weed of cropland and can form dense infestations in areas of native vegetation in which it can negatively impact upon native biodiversity.

T. diversifolia has been included in the Global Invasive Species Database (GISD 2008). It 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).

Management

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.

Tithonia diversifolia can be dug out when numbers are low. Slashing can result in re-sprouting from uncut stumps. Suitable herbicides can be applied as a foliar spray or a spot spray. When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

Research into biological control options for this species is being undertaken in South Africa (A.B.R. Witt pers. comm.).

Legislation

Not listed as a noxious weed by the state or governments in Kenya, Tanzania and Uganda.

References

Beentje, H.J. (1994). Kenya trees, shrubs and Lianas. National Museums of Kenya, Nairobi, Kenya, 722 pp.

GISD (2008). Global Invasive Species Database online data sheet. Tithonia diversifolia (shrub). www.issg.org/database. Accessed March 2011.

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.

ICRAF (1997) Using the wild sunflower, tithonia, in Kenya for soil fertility and crop yield improvement. International Centre for Research in Agroforestry.

Pacific Island Ecosystems at Risk (PIER). Tithonia diversifolia (Hemsl.) A.Gray, Asteraceae: plant threats to Pacific ecosystems. www.hear.org/pier/species/tithonia_diversifolia.htm. Institute of Pacific Islands Forestry, Hawaii, USA. Accessed March 2011.

Tropical Biology Association (2010). Usambara Invasive Plants - Amani Nature Reserve - www.tropical-biology.org/research/dip/species.htm.

Editors

Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.

Acknowledgments

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).

Contact

BioNET-EAFRINET Regional Coordinator: [email protected]