Effect of various plant growth substances viz., GA 3 (25, 50,100 ppm), ethrel (1500, 2000, 2500 ppm), copper sulphate (0.1, 0.2, 0.5%) as foliar spray treatment applied during January to October was studied at 15 days intervals. The flowering behaviour and sex-expression of Jatropha curcas was investigated during in randomized block design (RBD) at the College Farm, Navsari. Looking to the results, it was noticed that GA 3 50 ppm resulted in increased number of inflorescence per plant (31.25), number of flower per inflorescence (76.87), number of (male 94.75/female 4.01) flowers, flower sex ratio (24.22) in J. curcas. The Male: Female flower ratio was the lowest at 14 th spray stage under majority of treatments indicating increased number of female flowers which is ultimately reflected by increased fruit and seed yield of J. curcas.