What are photoperiodic cues?

A photoperiodic cue is a signal from the sun that tells plants and animals when to change what they’re doing, like growing or sleeping.

Imagine you have a favorite toy that only comes out when it’s dark outside. You know it's time to play with your toy because the lights go off, and the room gets cozy. That’s kind of how photoperiodic cues work for plants and animals, they watch the day and night cycle like you watch the lights.

During the day, sunlight is like a timer that tells creatures when to be active or rest. For example, some flowers only open up when there are enough hours of daylight, it's like they’re saying, “I want to show off my pretty face!” On the other hand, some animals hibernate during winter because the days get shorter and the nights grow longer.

Think about how you feel after a long day at school. You might be tired and ready for bed. Now imagine a tree feeling the same way, when the sun goes down and the sky turns dark, it’s time to rest too. And when the sun comes back up in the morning, it's time to wake up and grow again.

So photoperiodic cues are like little signals from the sun that help plants and animals know what time of year it is, without needing a calendar!