A root growth barrier and method for use with transplantable plants is provided. The barrier is a bilayer, comprising an inner layer of a root-tip-trapping material bonded to an outer layer of a root-impenetrable material. The inner layer faces the roots of a plant and serves to trap root tips to promote root branching. When a black or dark-colored inner layer is bonded to a white or light colored reflective outer layer, soil temperatures are lower and water retention is promoted. Such a barrier may be used as a freestanding container for plants or be manufactured into preformed rolls for use in plant pots and containers.