This study assessed herbicidal potential of Lantana (Lantana camara L.), on two commonly found paddy field weeds; Ludwigia decurrens Walt. and Ludwigia hyssopifolia (G. Don) Exell. Methodology involved a laboratory bioassay using 1:5 w/v and 1:10 w/v aqueous Lantana dried leaf extracts to assess germination, cotyledon expansion, root and shoot development of Ludwigia spp. Green house experiments included paddy soil amendments using 1g, 2g, 4g dried Lantana leaf residues in 85g soil and 30g, 60g, 120g residues in 2.5 kg paddy soil respectively to test seedling establishment and growth of Ludwigia spp. Toxicity of Lantana on rice (Oryza sativa) was tested by growing rice cv. 'BG 353' with L. decurrens in Lantana amended paddy soil. Toxic effects of Lantana on naturally occurring micro-biota were also assessed by diffusion method using 1.5 w/v Lantana dried leaf extracts on pure cultures of fungi and bacteria isolated from paddy soil. Results indicated that 1:5 w/v was the strongest extract to suppress root and shoot development of seedlings of both weeds. An amount of 4g Lantana leaf residue in 85g paddy soil suppressed germination and seedling establishment of L. hyssopifolia while higher quantities such as 120g of dried Lantana leaf residues in 2.5 paddy soil was required to suppress growth of L. decurrens. No potential harmful effects of Lantana were observed on growth of rice seedlings and microbiota of paddy soil. Higher quantities such as 120g in 2.5 paddy soil were required to suppress growth of L. decurrens.