Documentation of Invasive Plant Species along Roadsides in Ilorin Metropolis, Kwara State

Roadside habitats serve as important invasion corridors for exotic plant species in urban and peri-urban environments, and their characterisation in Ilorin metropolis, North Central Nigeria, provides baseline data for management planning. This study documented the invasive plant species occurring along four major roadsides in Ilorin metropolis: Ahmadu Bello Way, Ibrahim Taiwo Road, Unity Road, and Fate Road. Standardised 100m transects were surveyed at 200m intervals along each road, and all invasive or naturalised exotic species were recorded and identified. Frequency, cover, and occurrence data were compiled, and the invasiveness status of each species was cross-referenced with the Global Invasive Species Database. Thirty-one invasive and naturalised exotic plant species from 18 families were documented. Chromolaena odorata was the most widespread species, occurring on all four roadsides and covering an average of 24% of total ground cover where present. Other abundant invasives included Mimosa diplotricha, Tithonia diversifolia, and Senna obtusifolia. Roadsides adjacent to markets and informal settlements had significantly higher invasive species abundance. Native grass cover was inversely related to invasive herb density. Traffic intensity did not significantly predict invasive species richness. The study concludes that roadside habitats in Ilorin are heavily invaded, posing risks of spread into adjacent natural areas. A coordinated urban weed management programme integrating mechanical removal and revegetation with native species is recommended for the Kwara State Ministry of Environment.

Keywords: invasive plants, roadside habitats, Ilorin, Chromolaena odorata, urban ecology