Solanum seaforthianum (Brazilian Nightshade)

Scientific name

Solanum seaforthianum Andrews

Synonyms

Solanum seaforthianum var. disjunctum O.E. Schulz

Common names

Brazilian nightshade, vining solanum potato creeper, St Vincent lilac

Family

Solanaceae

Origin

This species is believed to be native to south-eastern USA, Mexico and parts of tropical South America (Venezuela and Colombia).

Naturalised distribution (global)

Locations within which Solanum seaforthianum is naturalised include Australia, tropical and southern Africa, eastern Asia and on some Pacific islands (e.g. Hawaii and New Caledonia).

Introduced, naturalised or invasive in East Africa

Solanum seaforthianum is invasive in parts of Kenya (A.B.R. Witt pers. obs.). The editors are not aware of records of the presence of S. seaforthianum in Tanzania and Uganda, though this does not necessarily mean that it is absent from these countries.

Habitat

A weed of untended areas with fertile soils. It is a weed of closed forests, forest margins, urban bushland, riparian zones (banks of watercourses), crops, roadsides, disturbed sites and waste areas.

Description

Solanum seaforthianum is a long-lived (perennialvine with climbing or sprawling stems, often covering fences or shrubs, reaching 5 m in height.

The stems are green and mostly hairless (glabrous), however there are often a few sticky (glandular) hairs on the flowering branches.

The alternately arranged leaves are borne on stalks (petioles) 0.5-6 cm long. Their leaf blades (4-13 cm long and 3-11 cm wide) are either deeply incised (pinnatisect), creating 3-9 lobes each up to 3.5-4.5 cm long and 1-2 cm wide, or appear to be once-compound (pinnate). Both leaf surfaces are green and hairless (glabrous), except for a few hairs on their margins and along the veins on either surface. The tips of their lobes may be either rounded or pointed (they have obtuse to acuminate apices).

The star-like flowers (2-3 cm across) are arranged in large branched clusters in the leaf forks (axils), each cluster containing 10-50 flowers. The main stalk (peduncle) of these clusters is 1-6 cm long, while each individual flower is borne on a smaller stalk (pedicel) 8-15 mm long. These flowers have five blue, violet or purple petals that are joined together at the base and have triangular tips (10-15 mm long). They also have five small green sepals (1.5-2.5 mm long), five stamens with yellow anthers (3-4 mm long), and an ovary topped with a style (6.5-8 mm long) and stigma.

The shiny globular berries (8-12 mm across) turn from green to bright red as they mature. They contain numerous reddish-brown to black flattened seeds (2-3 mm long).

Reproduction and dispersal

This species reproduces mainly by seed, which are most often dispersed by birds and other animals that eat the fleshy fruit.

Economic and other uses

Solanum seaforthianum is a garden ornamental plant. However, this cannot compensate for this plant's overall negative impacts.

Environmental and other impacts

Solanum seaforthianum is a weed of crops and other habitats. Its berries are reported to be poisonous to poultry, pigs, cattle, sheep and children (Howard 1979).

S. seaforthianum 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.

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.

The editors could not find any specific information on the management of this species. However, practical experience relates that it can be controlled by intensive and repetitive weeding and it is likely that herbicides would be effective applied as foliar, basal bark (painting herbicide onto the bark) or cut stump applications. When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

Legislation

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

References

GISD (2008). Global Invasive Species Database online data sheet. Solanum seaforthianum (vine, climber). 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.

Howard, R.A. (1979). Early botanical records from the West Indies, particularly Barbados: Ligon (1657) to Lord Seaforth (1806). Botanical Journal of the Linnean Society 79: 65-96.

Janaki-Ammal, E.K. and Viswanathan, T.V. (1975). A new garden plant for India: tetraploid Solanum seaforthianum. Indian Horticulture 25.

Pacific Island Ecosystems at Risk (PIER). Solanum seaforthianum Andrews, Solanaceae: plant threats to Pacific ecosystems. www.hear.org/pier/species/solanum_seaforthianum.htm. Institute of Pacific Islands Forestry, Hawaii, USA. Accessed March 2011.

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: eafrinet@africaonline.co.ke