The objective was to study the flowering response of garden cultivars of Dendranthemum × grandiflorum (Ramat.) Kitamura to temperature and photoperiod. Fifteen garden mum cultivars were grown in ten temperature (18 and 24°C constant day and night greenhouse temperatures) and photoperiod (8, 10, 12, 14, and 16 h) combinations. Rooted cuttings were pinched above the fifth node and placed in the temperature/photoperiod treatments. When axillary shoots developed, all but one shoot was removed to produce a single stemmed plant. Photoperiods were provided by delivering 8 h sunlight, then pulling black cloth and providing daylength extension with incandescent bulbs. Days to visible bud, days to first bud color, days to flower, node number, and stem length were measured. By 11 weeks after the start of photoperiod treatments, no difference was measured in days to flower in the 8-, 10-, and 12-h photoperiods at 18°C. Days to flower increased as photoperiod increased from 12 to 14 h. At 18°C, five cultivars flowered in the 16-h photoperiod, while 10 cultivars developed crown buds, i.e., flower buds that initiated but had not developed. At 24°C, there was no difference in days to flower in the 8and 10-h photoperiod, while days to flower increased as photoperiod increased from 10to 12-h treatment. Cultivars formed crown buds but had not reached flowering in the 14and 16-h photoperiods at 24°C. Regardless of temperature, stem length increased as photoperiod increased above 10 h.