PURPOSE: To obtain a plant growth accelerator suitable for plants and their seeds is Solanaceae, true grasses and Cruciferae, by using a specific norditerpene extracted from Nagi tree, a Chinese black pine, as an active ingredient to grow up in a short time.

CONSTITUTION: The subject plant growth accelerator contains, as an active ingredient, a norditerpene of formula I (R1WR3 are H, hydroxyl, R and R2 or R2 and R3 incorporate respectively to form epoxy group) such as nagilactone F of formula II or nagilactones X of formulas III and IV. The plant growth accelerator can be applied to tomato seeds, tomato, fruits, rice plant seeds and vegetable seeds in the form of an aqueous solution of preferably 0.05W50ppm.