PURPOSE: To continuously feed water and fertilizer ingredient to root of transplanted tree, promote rooting of tree and prevent dying by transplantation by arranging a rearing promoter obtained by charging a water-retaining material in a bag around the root pot of tree in planting hole and embedding the plant root into soil.

CONSTITUTION: A growth-promoting material (e.g. permiculite and fertilizer) 3 is packed into a cylindrical bag 2 made of nonwoven fabric (e.g. staple fiber), e.g. having 0.1-0.3mm thickness, 20kg/5cm tensile strength and 10-300cc/cm/sec air permeability to form a rearing promoter 1. The rearing promoter 1 is arranged around a root pot 5 of tree 4 and embedded into soil. According to the above-mentioned method, handling is made easy, because the water retaining material is put in the bag and sprinkling frequency after transplanting can be reduced and control is made easy.