In addition to the aesthetic and practical benefits of mulching, studies have shown indirect benefits of organic mulches to tree establishment and growth. These indirect benefits are associated with direct improvements on soil water and nutrient availability by mulches. The generalization of the organic mulches benefit to soil and trees has been questioned by several studies showing contradictory results under different experimental conditions and mulching materials. In addition, overall benefits for trees may be overlooked by focusing studies on some aspects of plant performance (e.g., plant growing rate) while ignoring others (e.g., plant chemical defense). This paper reviews studies showing how organic mulches can directly affect plant resource availability in the soil, presenting evidence from the literature that illustrates the influence of organic mulches on plant resource availability can also affect tree photosynthate allocation dynamics with direct consequences on plant chemical defenses. Based on the reviewed literature, presented here is a mechanistic pathway to illustrate how organic mulches can influence plant resources in the soil, and in turn how that can affect tree physiology and tree-insect interactions in urban areas.