PURPOSE: To promote growth after transplanting and increase the number of stems and further the fresh weight as a whole, by treating paddy rice seeds before hastening of germination with an effective amount of brassinolide.

CONSTITUTION: Paddy rice seeds before hastening of germination are treated with (2α,3α,22R,23R)-tetraphdroxy-24S-methyl-B-homo-7-oxa-5α-cholestan-6-one (brassinolide) expressed by the formula as an active constituent. In use, the form of an aqueous solution is preferred and the concentration thereof is 10-6W102 ppm, preferably 10-5W1 ppm. An aqueous solution of the active constituent is produced by dissolving the active constituent in a solvent dissolving the constituent, e.g. ethanol or isopropanol, diluting the resultant solution with water to a given concentration for treatment. The seeds are preferably treated by a method for dipping the seeds in an aqueous solution of the brassinolide preferably for ≥5 hr.