This study investigated the allelopathic effect of Chromolaena odorata foliage used as soil amendments on the leaf area, plant height, number of leaves, plant biomass and total chlorophyll content of Solanum lycopersicum, Mucuna pruriens, Abelmuschus esculentus, and Citrullus lanatus. Seeds of the test crops were planted in pots amended with 0%w/w, 1.9%w/w, 3.8%w/w, 5.7%w/w and 7.7%w/w of foliage of C. odorata and parameters as leaf area, plant height, number of leaves, plant biomass and total chlorophyll content were measured. The data collated were analysed using analysis of variance and the means separated using Tukey’s HSD. The leaf area, plant height, number of leaves and plant biomass showed a seemingly concentration-dependent, statistically significant increase in C. lanatus, S. lycopersicum and A. esculentus for all treatments, when compared to the 0%w/w treatment; and, although showing a visual and graphical increase for, M. pruriens, the increase in leaf area, plant height, number of leaves and plant biomass of M. pruriens were not statistically significant at 5% level of probability. The total chlorophyll content of all the plants studied showed concentration-dependent, statistically significant increments at 5% levels of probability when compared to their respective 0%w/w treatments. The increase in the leaf area, plant height, number of leaves, plant biomass, and total chlorophyll content of C. lanatus, S. lycopersicum, A. esculentus and M. pruriens due to the soil amendment with different amounts of C. odorata foliage is attributed to the possible effect of the allelochemicals in the leaves, which, although having a negative inhibitory effect on germination, had possibly undergone a bio-transformation to become stimulatory. Again, the foliar amendments increased the organic matter content of the soil, and thus, in synergy with the bio-transformed allelochemicals, serve as a bio-fertilizer to improve the growth of the test crops. Owing to the possible inhibitory effect of C. odorata foliage on the germination of these same test crops, it is therefore recommended that the foliage of C. odorata should only be used as organic manure or bio-fertilizer only at the post-germination stage of the test crops, not at the pre-germination stage.