The role of forestry plantation residues (leaf and branch) in the suppression of establishment of four weed species (Conyza sumatrensis, Trifolium spp., Echinochloa uti/is and Lactica sativa) was investigated. Of the three residue types used, Pinus
patula residues were found to have the greatest suppressive effects, followed by Eucalyptus grandis and then Acacia mearnsii. Medium-grade residue was found to be more effective than either the coarse or fine grades, and positioning the weed seeds below the mulch resulted in greater suppression than when placed above it. Water extracts from the three residues also resulted in significant suppression of weed establishment, suggesting an allelopathic effect. Finally, suppression of the dicotyledon species was generally greater than suppression of the grass used in this study.