Caesalpinia decapetala, commonly known as the Mauritius thorn is an Asian (India, Sri Lanka, China, Japan and Malaysia) tropical plant. It has been described as a robust, thorny, evergreen shrub two to four metres high or climber up to 10m high; often forming dense thickets.
The stems are covered with minute golden-hair; the stem thorns are straight to hooked, numerous, and not in regular rows or confined to nodes. The leaves are dark green, paler beneath, not glossy, up to 300 mm long; leaflets up to 8 mm wide.
The flowers are pale yellow, in elongated, erect clusters 100-400 mm long. Fruits are brown, woody pods, flattened, unsegmented, smooth, and sharply beaked at apex, ± 80 mm long. This plant falls under the category one plants of the Conservation of Agricultural Resources Act (CARA).
Plants from this category are prohibited on any land or water surface in South Africa and must be controlled or eradicated where possible. Mauritius thorn has become a major invasive plant in South Africa. This deciduous, sprawling noxious shrub with numerous spines forms impenetrable thickets limiting animal movement and smothering other plants.
The medium-sized seeds may be dispersed by rodents and granivorous birds and one spread considerable distances by running water. Trailing branches root where they touch the ground. The invasion by this alien plant species displaces indigenous plants and animals, reduces the productive potential of the land and impacts on biodiversity. Mauritius thorn invades disturbed areas, forests margins, plantations, roadsides, grasslands and watercourses. It was brought to South Africa for ornamental purposes and as security hedging.
Caesalpinia decapetala has been recorded inside and outside Kruger National Park as well as in other areas in the lowveld. The control of this plant is by herbicide and biological control. Should you have Mauritius thorn in your area, contact the Invasive Species Control Unit/Working for Water KNP on 013 735 4114/ 4376 for further investigation and clearing assistance.
References 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. Agricultural Research Council, Pretoria