For the most part, these stimuli provide information about the time of year, insuring that flowering only occurs during seasons that are advantageous for the reproduction of that species. The internal state of a plant also influence its ability to flower. A plant can not flower until has reached a certain state of developmental maturity. Once it is mature, the plant still must have internal mechanisms for receiving and evaluating the extrinsic cues that induce flowering. One such mechanism is its circadian rhythm, discussed below.
Most plants begin to flower when they first experience a night period of a particular length.
Each short-day plant species has its own specific threshold value for the minimum night length that will induce flowering. For most short-day plants in the wild, the length of the night will first reach its threshold value in autumn or winter, and typically at the most polar latitudes at which that species is found. Nights will continue to get longer as the year proceeds, and therefore the onset of flowering will sweep through the latitudes inhabited by that plant like a wave moving towards the equator. A short-day plant will not flower if the night's darkness is interrupted by even a brief flash of light. In other words, the plant does not flower in response to the actual length of time from sunset to sunrise, but rather to the longest period of unbroken darkness that it experiences.