What Do Plants Do at Night?

As the sun sets, plants seem to disappear. Trees overhead, grass underfoot, vegetable garden, meadow flowers—they all fade away into the shadows. They’re still there, of course, just like the stars are still overhead during the day—we just can’t see them. But plants are as awake and active at midnight as they are at noon. 

Plants don’t sleep as animals do—plants lack a brain and a central nervous system and all the neurological processes that true sleep involves. But plants are aware of day and night. Just like we do, they have circadian rhythms tuned to the cycle of light and darkness. Like animals, they do different things at night than they do during the day.

When the sun shines, plants make hay, so to speak—that is, they make food, which they then store up for later. Sunlight is required for the work of photosynthesis, the chemical reaction that magically turns air and water into food. At night, plants can’t photosynthesize—it takes a certain level of light to get the process going. But they don’t just hang around idly waiting for the sun to come up.

Instead, they respire, which is sort of a combination of eating and breathing. Respiration combines oxygen and the food created during photosynthesis to produce energy the plants use to grow. The sugars created during the day move around to different parts of the plant, where they’re burned to create the energy which powers growth. So you could say that plants make food during the day and eat it at night.

The process of respiration requires oxygen, so plants consume oxygen at night, although what they take in is a trivial amount compared to the huge amounts of oxygen they give off during the day.

So when you step into a garden or forest at night, you’re stepping into a wakeful world, churning with purpose and activity. All around you, plants are sucking in air, burning fuel, growing, feasting in the darkness. Listen. Can you hear them breathe?

To learn more about nature at night, please check out my book:

Wait Till It Gets Dark: A Kid’s Guide to Exploring the Night.

by Anita Sanchez and George Steele, illustrations by John Himmelman.