Plants know when to grow because of the change in temperature. As spring approaches, there will be an increase in temperature because the Earth is tilted towards the Sun. The temperature change is very noticeable for animals and plants too! When the seed or dormant plant senses that the temperature is increasing, it starts sprouting or growing new leaves. Sometimes, during the winter, the temperature can suddenly get warm for a few days and go back to being cold. Plants can still sprout or start growing leaves at this time, but later sense that this was a false alarm.