PURPOSE: To exactly perform greens-planting work for slope without decaying of buried plant in soil by adding rare earth element minerals to the base material.

CONSTITUTION: As breeding organs, e.g., nutrients and seeds of plants, seedling pieces 1 of a plant having creeping roots, e.g., wild soysia, etc., are used. The seedling pieces 1 are mixed with a spraying base material 2 mixed with a rare earth element mineral, e.g., radium ore, etc, for preventing the decaying of the seedling pieces 1, and the mixture is sprayed onto a slope. The germination and leaving of the plant can thus be accelerated, and therefore, greens-planting work can be exactly attained for slope.