An enthusistic outdoor movement in Joburg is seeing the removal of a harmful alien flora and replacing it with an indigenous grassland plant.
Volunteers from Jozi Trails have begun removing an aggressive invasive weed from the Florence Bloom Bird Sanctuary in Delta Park. The work marks the beginning of a long-term plan to improve the sanctuary and the greater Braamfontein Spruit area.
The target of the clean-up is Purpletop Vervain (Verbena bonariensis), a fast-spreading category 1b invasive that has taken hold along popular trail corridors.
While its purple flowers may look pretty and harmless, the plant crowds out indigenous grasses, spreads rapidly through seeding, and poses a threat to local biodiversity.
Once it establishes itself, verbena bonariensis pushes out endemic plants that insects, birds and animals rely on. It is also poisonous to livestock and herbivores.
Enter the wild cowpea
Jozi Trails volunteers have been manually removing the invasive weed by the roots – the most effective method – while carefully carrying the flowers off-site to prevent further seeding.
But the project isn’t just about clearing unwanted plants. To stabilise the soil and restore biodiversity, the team have been planting vigna vexillata. This is a hardy indigenous grassland species known to attract bees and butterflies.
Also called the Zombi pea or wild cowpea, vigna vexillata is a variable, perennial climbing plant that is pantropical, and often found in regions such as Ethiopia and Nigeria.
The flowers are pink or purplish to yellow and are sweetly scented. The stems of vigna vexillata tend to scramble over the ground and twine into the surrounding vegetation. This makes it effective in weed suppression.
The plant is being trialled as a natural replacement that can reclaim disturbed areas once invasive species are removed.
A win-win for trails and trail lovers
For Joburg’s trail users, the benefits go beyond conservation. Healthier indigenous vegetation helps reduce erosion, supports pollinators and creates more resilient green corridors.
Vigna vexillata is better suited to Joburg’s grassland ecosystem and the urban outdoor sections many residents rely on for recreation.
“This is the first of many removal efforts in the sanctuary,” Jozi Trails liaison officer Sam Brown told Randburg Sun.
“By restoring endemic plants and removing alien invasives, we hope to encourage more life back into Johannesburg’s green spaces.”
