Caesalpinia decapetala (Mysore Thorn)

Scientific name

Caesalpinia decapetala (Roth) Alson

Synonyms

Caesalpinia sepiaria Roxb.; Reichardia decapetalaRoth.

Common names

Mysore thorn, Mauritius thorn, cat's claw, wait-a-bit, mubage (Kikuyu), kitandambo (Kamba), olmashinga (Arusha)

Family

Fabaceae (Leguminosae): sub-family Caesalpinioideae

Origin

Native to southern and eastern Asia

Naturalised distribution (global)

Locations within which Caesalpinia decapetala is naturalised include much of Africa, several Pacific Islands, the Mascarenes (Mauritius, La Réunion and Rodrigues) and eastern, central and southern Africa.

Introduced, naturalised or invasive in East Africa

Caesalpinia decapetala is invasive in parts of Kenya (Maundu and Tegnas 2005, Global Invasive Species Database), Tanzania (Dawson et al. 2008, Henderson 2002) and Uganda (A.B.R. Witt pers. obs.). It is still being spread in the region as a life fence (hedge).

Habitat

Caesalpinia decapetala is regarded as a weed of forest margins, disturbed forests, wetter bushland areas, riparian zones (banks of watercourses), pastures, disturbed sites, wildlife, old gardens, roadsides and plantation crops in tropical and  subtropical regions.

Description

Caesalpinia decapetala is a  large sprawling shrub (growing up to 7m) with prickly branches (recurved prickles) that forms dense thickets; or a climber growing up into the canopy of larger trees (up to 20 m high).

The young branches are densely covered with tiny brownish or golden-coloured hairs and have numerous sharp recurved thorns. Older stems are thicker, greyish-brown in colour, and have larger thorns.

The leaves are twice-compound (bipinnate), alternately arranged, and have a pair of small leafy structures (stipules) at their base. These stipules (4-20 mm long) are egg-shaped in outline with broad end at base (ovate), but taper to a point (they have acute apices). The leaves are borne on stalks (petioles) 3-8 cm long. The extension of this stalk (the rachis) is slightly hairy (puberulent), prickly, and bears 4-10 pairs of branchlets (pinnae). Each of these branchlets (pinnae) has 8-12 pairs of leaflets (pinnules). The leaflets (7-20 mm long and 2-8 mm wide) are oblong or obovate (egg-shaped in outline but with the narrower end at the base) and somewhat hairy (pubescent) on both sides, dark green above, paler below.

The flowers are usually pale yellow or yellow in colour (occasionally whitish), with five petals (10-15 mm long), five sepals (9-10 mm long), ten stamens (10-16 mm long), and a style (15-20 mm long) topped with a cup-shaped (cupular) stigma. Four of the petals are almost circular (orbicular) in shape, but the upper petal is smaller and narrower than the others. The flowers are borne on stalks (pedicels) 15-25 mm long and arranged in upright (erect), elongated, clusters (10-40 in some cases they may reach 20 cm long) at the tips of the branches (in terminal racemes).

The fruits are flattened, oblong, pods with a small projection (beak) at one end. These woody pods (6-10 cm long and about 25 mm wide) are hairy (pubescent) and turn from green to brown as they mature. When they are fully mature, they split open to release 4-9 rounded (globular) seeds. These seeds (6-10 mm across) are brown and black in colour, persisting for many months and scattering seeds as they break open are scattered as the pod opens.

Reproduction and dispersal

This plant reproduces by seeds, which may be dispersed by animals (e.g. rodents and birds) and human activities (e.g. in dumped garden waste). The pods may also float on water. This species has been widely dispersed as hedge plants because they grow well in that situation and form an almost impenetrable barrier to livestock (and people).

Similar species

Caesalpinia decapetala is quite similar to Caesalpinia gilliesii (dwarf poinciana) and Caesalpinia pulcherrima (pride of Barbados). These species can be distinguished by the following differences:

  • C. gilliesii  unlike C. decapetala is non-prickly shrub, also with twice-compound (bi-pinnate) leaves but bearing slightly more (12-15) pairs of branchlets. Its yellow flowers have very long stamens (60 mm or more long) with distinctive bright red filaments. The elongated flower clusters (racemes) are covered in sticky hairs (they are glandular pubescent) and the flower petals are relatively large (20-25 mm long) compared with C. decapetala.
  • C. pulcherrima is also a prickly shrub with twice-compound (bi-pinnate) leaves bearing numerous pairs of branchlets. But, its bright yellow or red and yellow flowers have very long stamens (60 mm or more long) with yellow or bright red filaments unlike C. decapetala. The elongated flower clusters (racemes) are hairless (glabrous) and the showy flowers have relatively large petals (more than 25 mm long).

Economic and other uses

Caesalpinia decapetala has been introduced as a live fence. In parts of Uganda especially near protected areas, this species is used as a live hedge around gardens to keep off pests especially baboons and other primates due to its strong tough thorns (D.L.N. Hafashimana pers. comm.). It is also used for ornamental purposes. However, these uses cannot compensate for this plant's overall negative impacts.

Environmental and other impacts

Caesalpinia decapetala is an environmental weed in tropical and  subtropical regions. It invades forest edges and gaps preventing regeneration of native species and climbs into canopies and causes canopy collapse or death of trees. It can also invade native vegetation, pastures and grasslands and adversely affect the movement of livestock and some species of wildlife. C. decapetala can also engulf fences, sheds, bridges and other infrastructure and is difficult and dangerous to remove due the presence of sharp recurved thorns. Its dense thickets can restrict water flow, access and downstream movement of flood debris, leading to increased upstream flood damage. C. decapetala also invades in warmer temperate regions.

C. decapetala has been included in the Global Invasive Species Database (GISD 2010). 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) and in the Australian states of New South Wales.

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.

Seedlings and saplings can be dug up or pulled up manually but mechanical control of larger plants is very difficult because of their sharp thorns. Rootstocks will coppice if the roots are not removed or the cut stumps treated with herbicide. Caesalpinia decapetala is sensitive to foliar applications of suitable herbicides but it is very difficult to achieve adequate coverage in dense infestations. Timely repeat applications (every 3-9 months) allows gradual reductions and opening of the canopy and eventual control. Accessible stems may be painted with product suitable product in diesel or crop oil in very-low volume applications (basal bark treatment). When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

A seed feeding insect (Sulcobruchus bakeri - Bruchidae) have been released in South Africa for biological control of C. decapetala but has not been very effective (A.B.R. Witt pers. comm.). A leafmining moth is under evaluation as a possible biological control agent.

Legislation

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

References

CABI invasive species compendium online data sheet. Caesalpinia decapetala (Mysore thorn). CABI Publishing 2011. www.cabi.org/ISC. Accessed March 2011.

Dawson, W., Mndolwa, A.S., Burslem, D.F.R.P. and Hulme, P.E. (2008).  Assessing the risks of plant invasions arising from collections in tropical botanical gardens. Biodiversity and Conservation 17(8): 1979-1995.

Global Compendium of Weeds. www.hear.org/gcw. Hawaiian Ecosystems at Risk Project. Accessed March 2011.

GISD (2010). Global Invasive Species Database online data sheet. Caesalpinia decapetala (shrub, tree). www.issg.org/database. Invasive Species Specialist Group. 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.

Henderson, L. (2002). Problem plants in Ngorongoro Conservation Area. Final Report to the NCAA.

Maundu, P. and Tegnas, B. (2005). eds. Useful Trees and Shrubs for Kenya, World Agroforestry Centre, Nairobi.

Noad, T. and Birnie, A. (1990). A fully illustrated field guide: Trees of Kenya. 2nd ed. T.C. Noad and A. Birnie, Nairobi.

Pacific Island Ecosystems at Risk (PIER). Caesalpinia decapetala (Roth) Alston, Fabaceae (Leguminosae): plant threats to Pacific ecosystems. www.hear.org/Pier/species/caesalpinia_decapetala.htm. Institute of Pacific Islands Forestry, Hawaii, USA. Accessed March 2011.

Wikipedia contributors. "Caesalpinia decapetala." Wikipedia, The Free Encyclopedia. Accessed January 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