Roots of exotic and native tree species were exposed by digging trenches adjacent to tree stands in plantation at four vegetative zones of varying dryness and soil types (Afaka, Miango and Nimbia ) in Nigeria. Root size and distribution were measured and compared at three determined depths along the soil profiles. Although all the soil types have a layer of hard iron crust (plinthite layer) with in a depth of 40-60 cm in the soil the roots of the exotics were able to penetrate beyond the plinths. Among the exotic, Eucalypts proved best at penetrating the plinths, having comparatively larger sized and more numerous roots that were well distributed along the soil profile. Closely following the eucalypt were the pines. Roots of all trees studied at Nimbia grew better than those at other locations. This was attributed to the pisolitic nature of the Nimbia plinths which can go soft when wet but hard when dry as opposed to the continuously hard plinth types at the other localities. The relationships between root penetration tree growths, and the tree abilities to harness soil water during the dry season at different localities are discussed.