The image shows the deciduous large Jacaranda tree that grows up to 20-30 m high. The leaves are bipinnate produced in conspicuous large panicles, each flower with a five-lobed purple corolla. The fruit is oval flattened capsule containing numerous seeds. The Jacaranda in Pretoria flowers between September to November with purple flowers that paint the whole City purple. For this reason, Pretoria is called the Jacaranda city.
Known for its alluring lilac blossoms, the Jacaranda tree (Jacaranda mimosifolia) is native to South America and was introduced for decorative purposes way back in the 1800s to South Africa. In Pretoria, the Jacaranda was first introduced in Arcadia in 1888. Its beautiful flowers are characteristic of the springtime in Pretoria, City of Tshwane, Gauteng Province, where it fascinates the residents by putting a light purple carpet all over the roads.
Although the purple flowers remind the University students of the exams that take place around that time of the year, the elegant beauty of the Jacaranda flowers calms down the souls of many residents. Legend has it that when a flower from the Jacaranda tree drops on top of your head, you would pass all of your exams. Therefore, students wish for on eof the soft blossoms to drop one of its tubular flowers on their heads as they pass under this magical tree. The seeds, on the other hand, are enclosed in a brown, oval and flat capsule, which bursts open when dry, releasing flat winged seeds. They disseminate via wind dispersal to the savannah, woodlands, rocky ridges, riverbanks and all sorts of habitats.
To the conservationists, this deciduous beauty is an invasive species. Its origin is reported to be South America, particularly Argentina and /or Brazil because of the name’s Guarani origin in Argentina. The tree is regarded as an invasive species in South Africa and Australia. In South Africa, it is labelled as preventing growth of native species. However, in other parts of Africa such as Zambia, Zimbabwe and Kenya, the species is also present without being considered invasive yet.
In Pretoria, City of Tshwane, Gauteng province, the Jacaranda trees are enormous and line the pavement of the streets and inhabit roadsides, as evident in the images above. When they flower, they paint the whole City purple and it is spectacular to witness. The images portray the beauty and elegance of the tree that perhaps is draining the native ecosystem, which not to many are aware of.
Jacaranda blossoms are stunningly beautiful, but hidden underneath is the contradiction of the tree being an alien species that prevents indigenous trees from growing. Indeed, not “all that glitters is gold”. For this reason, the Jacaranda tree is no longer allowed to be planted in Pretoria.
Water scarcity is the most alarming problem of the twentieth century next to climate change in conservation. The sustainable Development Goal (SDG) 15 aims to protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss. In the meantime, SDG goal 11 promotes sustainable cities and communities. The dilemma of keeping the City green with trees and balancing the water ecosystems with the proper tree planting is a challenge that must be tackled through a multi-inter and trans-disciplinary approach to sustainable development. The Jacaranda tree is an example of this contradiction.
Apart from being beautiful ornamental trees, the Jacarandas' wood is used for furniture and other crafts. Meanwhile, programmes to address the social economic problems in communities were linked to alien species like the Jacaranda. These programmes aim at the sustainable management of natural resources through the control and management of alien invasive plants, by removing the species and thereby bringing employment to the youth, as part of the expanded Public Works Programme. The objective is to reduce the impact of invasive alien trees on water resources.
All over the world, trees and plants are introduced for various purposes. These trees contribute to multiple services for instance fodder, timber, medicines, fruits, shade and ornaments. Now as resources become scarce - especially water -, conflicts are beginning to emerge. Benefits and costs of these species are weighed against the endurance of the people and impact on the environment. Many strategies involve physical removal of alien vegetation. The benefit-cost analyses conducted so far have shown that the investment in clearing invasive species cost for example R116 in riparian areas, which equals about 6,40 US-Dollars (Marais and Wannenburgh (20008). However, it is important to remember that clearance seldomly results in total elimination.
- Jacaranda Jacaranda mimosifolia, retrieved from http://www.invasives.org.za/legislation/item/265-jacarandajacaranda-mimosifolia
- Marais, C and Wannenburgh, A.M. (20008) Restoration of water resources (natural capital) through the clearing of invasive alien plants from riparian areas in South Africa — Costs and water benefits.
- South African Journal of Botany 74 (2008) 526–537
- Bolsmann, E. (1997). Jacaranda – Pride of Pretoria. Pub Be My Guest Publishers, Pretoria pp. 40.
- Potgieter, M.J and A.Samie (2019). Ethnobotanical survey of invasive alien plant species used in the treatment of sexually transmitted infections in Waterberg District, South Africa, retrieved from: https://doi.org/10.1016/j.sajb.2019.01.012
published May 2020