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• The effect of co-planting on plant growth was associated with root morphology changes. • The changes of plant growth and root morphology affected metal accumulation. • Species develop an active, passive, or avoidance strategy to phytoremediation in different co-planting systems. • Plant-plant interaction is more critical than individual plant potential for successful phytoremediation in co-planting systems. • Co-planting with an active strategy is applicable for sludge-contaminated soil phytoremediation. Recycling sewage sludge (SS) as a soil amendment potentially causes soil heavy metals (HMs) contamination. This study investigated the potential roles of landscape plants co-planting in SS-amended soil remediation. Three landscape trees Mangifera persiciforma , Bischofia javanica , and Neolamarckia cadamba (NC), and three ground cover plants Dianella ensifolia , Syngonium podophyllum , and Schefflera odorata (SO) were selected for the tree-ground cover co-planting. Species in different co-planting treatments exhibited diversified effects on the growth, root morphology, HMs uptake, and HMs accumulation. Five plant characteristics including total root length, total surface of roots (diameter <2 mm), specific root length, shoot dry weight and root dry weight played crucial roles in plant HMs uptake. Structural equation modeling analysis revealed that different co-planting treatments drive species to develop an active, passive, or avoidance strategy to accumulate HMs, resulting in a diversity of HMs removal efficiency. Co-planting of NC with SO promoted NC and SO HMs accumulation and resulted in the greatest HMs contents decline (48.0% for Cd, 24.9% for Cu, 33.8% for Zn, and 27.2% for Ni) and the lowest potential ecological risk. Co-planting of landscape tree and ground cover plants with an active strategy can be a potential candidate for HMs phytoremediation of SS-amended soil. [ABSTRACT FROM AUTHOR]