Global warming has changed the suitability of traditional planting areas of crops, raising concerns about cereal security. To investigate the possibilities and constraints of increasing yields by breaking through traditional planting area of wheat, a two-year field experiment was conducted in southern and northern locations in the Yangtze River basin (YRB), China (separated by approximately 180 km), with seven weak-winter-type and six semi-winter-type wheat cultivars, respectively, bred for the two regions. Moving weak-winter-type cultivars to the north increased grain yield, however, the grain yield increase was different in two years, and their grain yields were not significantly higher than those of local semi-winter-type cultivars. Moving semi-winter-type cultivars to the south significantly decreased their yields. Thus, breaking through traditional plantings of wheat did not significantly increase grain yields compared with those of local wheat cultivars, and even limited the potential of wheat grain yield. Grain yield of wheat planted in the northern YRB was 5% to 20% higher than that in the southern YRB because of more spikes (from 8% to 50%) which were increased by high main stem and tiller survival resulted from a longer vegetative growth phase, but too more spikes decreased the single-spike yield (from 1% to 15%). The change of vegetative growth phase among wheat cultivars in the two sites did not significantly affect the maximum stem and tiller number. In addition, the high main stem and tiller survival delayed the decline of post-anthesis photosynthetic area which was conducive to increase biomass after anthesis in the northern YRB. High-yielding cultivars always had more spikes and larger photosynthetic areas after anthesis than those of low-yielding cultivars regardless of the planting location, which led to increases in post-anthesis biomass. However, grain yield of different cultivars was highly variable under different ecological conditions. The coefficient of variation (CV) of grain yield in different cultivars was significantly positively correlated with the CV of spike number and post-anthesis biomass, and negatively correlated with the CV of single-spike yield, suggesting that flexibility in spike number, post-anthesis biomass, and stability single-spike yield in response to environmental changes can maximize release of yield potential. Therefore, improving main stem and tiller survival can increase spike number and maintain large post-anthesis photosynthetic area, and help to establish large, highly stable and productive populations that high effectively use resources during the late growth phase to achieve high grain yield. The present results could provide valuable suggestions for breeding high-yield cultivars and determining the planting area in the future.