Tissue culture of D. alata cv Lupias, supplies in all seasons plant lets of which morphology and development patterns present some similarities with seedlings of closely related species. Plantings, irrigated and staggered between september and april show that later behaviour of those plant lets depends on planting season. Two effects are observed : On one hand a reduction of maximum development attained by aerial and underground parts after planting under short or decreasing days on the other hand a certain regrouping of dieback dates of aerial parts for all plantings and a regrouping still more drastic of sprouting dates. The first effect brings about a yield reduction as compared to april planting, sensitive since september and very severe from october to december plantings. The second effect annihilated since next year the initial temporal shift induced by out of season planting. The results are very close of those obtained generally with staggered plantings from yam tubers of D. alata presenti 19 signs more or less accused of ageing. As they cannot be here attribued to the mother tuber, we conclude that the difficulty of out of season cultivation of that species is due to a great sensitiveness to environmental factors, (thermo-photo-periodism).