Ailanthus roots are shallow spreading,  often apparent at the soil surface, and roots near the trunk  thicken into enlarged storage structures. These large rounded  structures are assumed to be for water storage, contributing to  the drought hardiness of the species (4). There is a general  absence of a taproot with most roots present in the upper 46 cm  (18 in) of soil. Within this zone, the deeper roots send numerous  small roots to the surface. Adventitious shoots may arise from  any of the surface roots.