PURPOSE: To simply form the ground to grow plants over a wide area by a method in which many trenches of given depth and length are excavated in the sloped ground by jetting high-pressure water and greens-planting materials such as replaced soil, fertilizers, etc., are packed into the trenches.

CONSTITUTION: Long trenches 2 nearly traversing the slope are excavated at given intervals vertically in the sloped ground by jetting high-pressure water from a nozzle. The width, depth and mutual distance of the long trenches 2 are selected according to the species of plants and the properties of the ground. After the excavation, a greens-planting material 3 prepared by mixing replaced soil with fertilizers, fibrous materials, etc., is packed into the trenches 2. The ground to grow plants can thus be very simply formed in the sloped ground with good efficiency and the strength of the surrounding ground can be maintained without degradation.