A field experiment was conducted during 1984-86 to study the effect of planting time (planted on the 15th day of each month from January to July) on plant survival, tuber development and tuber yield of a 2-year crop of medicinal Yam (Dioscorea floribunda Mart & Gal) under the sub-tropical climate at Lucknow, India. Yams planted during January, February and March, using tuber dug on the same day, recorded 35-40% plant survival at harvest, gave 350-410 mg/plant/day rate of tuberization (dry weight basis) and yielded 60-65 q/ha dry tuber, as against 25% plant survival, 365-425 mg/plant/day rate of tuberization and 35-42 q/ha tuber yield, obtained from June and July planting, using pre-sprouted tubers (conventional practice). The May planted crop had the lowest plant survival (8.9%) as well as tuber yield (9 3 q/ha), The results are discussed in relation to temperature and humidity effects on sprouting and tuber development.