The correct answer to this question is either Spring or Fall. Short Day plants are one of the three categories of plants that are based on how much sunlight is needed for the to thrive. The other two categories are long-day plants and neutral-day plants. Plants that are short day are when the day length is less than the photoperiod.
This occurs in either the spring or Fall, while Long-day plants flower in the summer. There are many short day plants. Two main examples are poinsettias and chrysanthemum. Poinsettias day length is 10 hours, while chrysanthemum's day length is 15 hours.