The increase in the number of flowers under ND or ND + 14HIDduring ST 2 suggests that flower initiation and development from about 45-d old plants probably occurs between 45 and 85 d after sowing at average daily temperatures of 16-24.C. No difference in flower numbers among irradiance levels given for 40 d (Expt.2) suggests that flower bud initiation may be completed between 80 and 120 d after sowing (Expt. 1). Flower bud development may be affected by high irradiance treatment during ST 2 coupled with high greenhouse temperatures (ca. 24-27.C) prevailing between July and September (ST 2). Favretti (1955) reported thatwith S. speciosa var. Hannestad propagated from leaf cuttings in November, flower bud production was increased with irradiance up to 2000 ft-c.