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How Do Plants Wake Up and Go to Sleep?

Plants Wake Up and Go to Sleep

Just like humans, plants require a regular sleep cycle in order to be their healthiest and most productive selves. The rules are a little different, as plants are not regulated by a central nervous system, but the bottom line is: if you’re a grower, you should take your plants’ sleep cycle as seriously as you do your own.

Many flowering plants are “diurnal,” which means they depend on a cycle of light and darkness for their cues to grow and develop. They are also “photoperiodic”—they take physiological cues from the way light changes over the course of a season. All this to say: the health and productivity of your plants depends on a specific balance of dark and light. And if you understand exactly what your plants need, your odds of giving them the best possible care increase considerably.

Plants and the Circadian Clock


If you’ve ever had trouble regulating your own sleep cycle, you’re probably already familiar with melatonin. It’s usually the first advice anyone gives to a person who has trouble falling asleep. “Take melatonin.”

This is because melatonin is the hormone that stimulates sleep, and our bodies are triggered to produce melatonin when darkness sets in. 

Plants have a similar routine going, but in their case, darkness triggers production of the hormone auxin. This hormone controls growth and development, and when night falls and auxin levels increase, the plant knows it’s time to stop the process of photosynthesis and focus instead on metabolizing the energy they made during the day.

This regulated cycle of light and dark, gathering energy and using energy is called the “circadian clock”—a 24-cycle that controls biological functions.

Why Do Plants Need Sleep?


So, what exactly are these biological functions? What happens when your plants sleep?

If you’re a grower, you already know how important daylight is to your plants. Whether you use the sun or a system of indoor grow lights, you know your crop needs plenty of time to soak up those photons and turn sunlight into food. But what happens to your plants when the sun goes down or the lights go out?

When darkness sets in, your plants stop the process of photosynthesis and turn their focus to growth. They take all that energy they consumed and put it into growth, root development, and flowering. Night time is basically an opportunity to catch up. It’s the moment when your plants reap the benefits of the day’s hard work. 

And just like humans, plants require ideal conditions in order to get the sleep they need. Light pollution confuses them, creates stress, and disrupts flowering. To make sure your crop has the best shot at producing high yields and healthy buds, you want to give them pitch black sleeping conditions. If you’re a greenhouse grower, a system for covering your plants at night is highly recommended. 

How Plants Respond to Changes in Sunlight


What’s particularly fascinating about plants is their circadian clock is far more nuanced than just “lights on/lights off.” There are physiological changes that occur in plants throughout each stage of the day, and your crops take note when the days grow shorter. Shorter days tell them the season is coming to an end and they’d better get to flowering before they lose their chance. 

Even more impressive, your crop’s sensitivity to light cycles is so exact that they may even anticipate predators. Studies have shown that plants pick up on the daily cycle of bugs and other pests. Once the plants know what time of day predators are likely to show up, they launch a chemical defense in anticipation of those intruders. In other words, a carefully regulated and consistent cycle of daylight can actually be a form of pest control. Pretty incredible, right? 

How to Work with Your Plants’ Circadian Clock


It’s clear enough that nature has already set your plants up for success. They know what they’re doing. It’s up to you as an indoor or greenhouse grower to provide the cues they would normally get from the sun. 

A spectrum variable LED grow light is extremely helpful when it comes to replicating natural day/night cycles. This kind of technology allows you to mimic sunrise and sunset and adjust both the intensity and light spectrum throughout the day, tapping into your plants’ ability to take physiological cues as the day progresses. In fact, a unit like the SolarSystem Controller allows you to pre-program a 365-day light cycle down to the minute, ensuring total consistency and natural transitions through the growth cycle. 

Another important step is to do the research to understand the ideal light/dark balance for your plants’ current stage of growth. We’ve provided some of that information on our blog, but we know this topic can get complicated, so please don’t hesitate to reach out with any questions you have about tending to your crop’s circadian clock. 

The bottom line is to remember that your plants need to rest and recharge just like you do. Learn when to blast them with light and when to bathe them in darkness, and you’ll wind up with happy plants and a quality product. 


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