Yes, your plants respire at night just like they do during the day without pause. This process runs 24 hours a day in every living cell of your plants. When the sun goes down, your plants keep burning glucose and using oxygen to make energy. The only thing that stops is photosynthesis since it needs light to work. Nighttime plant respiration keeps your plants alive and well until the sun comes back up in the morning.
When I first set up a CO2 meter in my plant room, I saw a clear pattern each day. During daylight hours, the CO2 levels dropped as my plants pulled gas from the air for photosynthesis. After dark, the readings climbed back up bit by bit as the plants released CO2 instead. This showed me that plant CO2 at night is a real and normal part of how plants live and breathe around the clock.
During the day, your plants run two processes at once that work against each other. Photosynthesis pulls in CO2 and pushes out oxygen while making sugar from light. Respiration does the reverse by using oxygen and sugar to make energy. In bright light, photosynthesis runs faster and wins out. Your plant gives off more oxygen than it takes in. At night, only respiration runs so your plant releases a small net amount of CO2 into the air around it.
Scientists call this process dark respiration to set it apart from what happens in the light. The name doesn't mean the process changes when darkness falls on your garden. It just points to the fact that you can measure respiration alone once photosynthesis stops. In my experience, knowing about dark respiration helps you see why plants in low light may weaken over time. They keep burning energy but can't make enough to replace what they use.
You may have heard the old tale that sleeping near plants is bad for your health. People used to say that plants would steal your oxygen and fill the room with CO2 while you slept. This myth has no basis in fact at all. A typical houseplant uses such a tiny amount of oxygen that you would never notice it. Your own breathing moves far more air in one minute than a plant uses in a full night of dark respiration.
I tested this idea by tracking oxygen levels in my sealed bedroom with and without plants. The difference was too small to even show up on my meter. A human uses about 250 mL of oxygen per minute just sitting still. A small potted plant might use a few mL per hour at most when respiring. You would need hundreds of plants crammed into a tiny closet before oxygen levels would drop enough to matter to your health.
Greenhouses tell a different story since they pack so many plants into one space. Growers often add extra fans that run at night to keep air moving and fresh throughout the space. Without good airflow, CO2 can build up in pockets near the plants and slow growth the next day. You won't have this problem in your home since normal air leaks and HVAC systems move more than enough air to handle your houseplants.
Your plants respiring at night is part of their normal life cycle and nothing to worry about at all. Give them good light during the day so they can stockpile enough sugar to last the night. Keep air moving in your plant room if you have a lot of greenery packed into one spot. With these simple steps, your plants will thrive around the clock and keep your indoor air fresh and clean.
Read the full article: Respiration in Plants: The Complete Process Guide
