The landscape and turf industries are based on beauty. Some trees in the landscape suppress the growth of any other plant species beneath them. This is reported to be caused by allelochemicals which are released into the soil by the plants, a mechanism known as allelopathy. Soil amendment is therefore needed to curb the effects of these allelochemicals and make the nutrients in the soil available to other plant species that may be planted beneath the allelopathic trees. Biochar is a fine-grained, highly-porous charcoal substance that is used as a soil amendment. This study was conducted to find out the ameliorative effect of biochar in the allelochemical-laden soils to improve on the soil physicochemical properties and also to suppress the effect of allelochemicals in the soil. Biochar produced from Tectona grandis (Teak), Celtis mildbraedii (Esa), and Entandrophragma cylindricum (Sapele) and absolute control were the treatments used. The treatments were applied to the soil at a depth of 3 inches at a ratio of 1:1. The study was carried out beneath a bamboo stand – a tree species suspected to be allelopathic. Stenotaphrum secundatum (St. Augustine’s grass) was used for the study because it prefers shaded growing environmental conditions. The experimental design employed was randomized complete block design and the experiment was replicated three times. Data collected over a period of twelve weeks included presence of allelochemicals in the soil and in the tree species, soil physicochemical analysis, rate of growth and percentage coverage of grass. The results of the study indicated that the bamboo species is allelopathic. Biochar was able to reduce the effects of the allelochemicals and hence allowed the grass to grow well. The amendments also improved upon the soil’s physicochemical properties.