The quality of any agronomic product depends on the physiological performance of the crop, but limitations to optimal performance under the highly variable growth environment within a typical agricultural crop canopy are often not clear. Controlled-environment studies have demonstrated that the physiological factors important in cotton (Gossypium sps.) fiber synthesis depend on environmental constraints, especially temperature and available energy in the form of reduced carbohydrates from photosynthesis or stored reserves. In this study, we examined fiber development in two cotton species, G. hirsutum and G. barbadense under field growth conditions. The sensitivity of boll period to growth temperature indicate that a one degree shift in average daily temperature experienced during the boll development period would alter the duration of the maturation by 5 days. However, differences in average daily growth temperature also resulted in changes in dry weight accumulation and composition pattern of fruit components, particularly of the fiber and seed. Control of bur development was insensitive to growth environment and independent of fiber development. Lack of coordination between fiber growth factors and boll maturity (as indicated by bur opening) can result in substantial reductions from optimal fiber quality upon harvest, and indicates a need for a better measure of crop maturity than the rate of fruit dehiscence.