How Do Greenhouses Affect Photosynthesis?

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How Do Greenhouses Affect Photosynthesis

We eat food to get our nutrients and grow. For plants, that end is achieved through photosynthesis.

Simply put, photosynthesis is the process plants go through to use sunlight to create their own food. They do this with carbon dioxide and water.

In an outdoor situation, it’s easy to see how all the requirements for photosynthesis are met. Plants get plenty of water from their native environments, and they usually get lots of sunlight, too.

But more and more people are gardening in greenhouses these days, because it can extend the growing season and protect delicate plants. Because of this, you might be asking yourself: how do greenhouses affect photosynthesis?

In this article, we’ll examine whether or not greenhouses have an impact on photosynthesis, as well as how to ensure your plants get everything they need to feed themselves.

Quick Answer: How do Greenhouses Affect Photosynthesis?

Plants need sufficient light, water, and carbon dioxide to photosynthesize properly. Greenhouses are designed to admit light, but gardeners are responsible for factoring in the water and carbon dioxide.

Ventilating the greenhouse and circulating air from outside can help plants get enough carbon dioxide. Other gardeners may choose to use CO2 generators.

Related Article: Why Do Greenhouses Use Purple Lights?

What Do Plants Need to Photosynthesize Properly?

Now that you have a general overview of how greenhouses can impact photosynthesis, let’s take a closer look at how the process works. That way, you’ll have a better understanding of what you can do to keep your plants healthy.

Photosynthesis requires three main things:

  • Light
  • Water
  • Carbon dioxide

We’ll discuss each of these necessities in a little more detail below.


Sunlight is crucial to photosynthesis. Without it, plants simply could not convert water and carbon dioxide to the nutrition they need.

Usually, they get this light from their natural exposure to the outdoors. In a greenhouse, the majority of it will come from panels designed to diffuse the available light.

Related Article: Best Greenhouses for Southern California


There are a few ways in which the lack of water impedes photosynthesis. Sometimes, even when there’s plenty of water around, it can still fail to help a plant with the process.

For instance, if the plant isn’t able to absorb the water due to a lack of root growth, any water in the environment is essentially useless. Excessive humidity can also disrupt photosynthesis, because transpiration cannot occur properly when the air is too moist.

When neither of those situations describes your greenhouse, lack of water will be one of the biggest obstacles to photosynthesis. This occurs when plants don’t get enough water around their roots.

Carbon Dioxide

Finally, CO2 is integral to photosynthesis. When there’s not enough of it in the air, your plant cannot get the nutrition is needs.

This is especially common in tightly sealed greenhouses in the middle of the winter. Because air isn’t getting in, but sunlight still is, photosynthesis can be drastically impaired in these conditions.

How Can You Provide Everything a Plant Needs to Photosynthesize in a Greenhouse?

"there are a lot of actions you can take to ensure your plants get everything they need to photosynthesize healthily."

Fortunately, there are a lot of actions you can take to ensure your plants get everything they need to photosynthesize healthily.

Watering can be fairly simple. You’ll just need to research exactly how much water your plants need, and supply that to them appropriately. Some greenhouses have misting systems in them that do the watering for you, and others use external gutters to store rainwater that you can use later.

Sunlight can sometimes get tricky to supply to your plants. Depending on where you live, you may or may not get plenty of sunlight for your garden.

If you’re living somewhere with long, cold winters where sunny days are in short supply, you can consider using grow lights to supplement your plants’ sun intake.

When it comes to CO2, bringing in air from outside will probably be your best bet. This means opening vents and circulating the air throughout your greenhouse with things like fans. During the winter, this is still possible, but you may need to consider using a heater to warm the air once it’s inside the greenhouse.

Read Also: Best Greenhouses for Winter Growing 

Wrap Up

Greenhouses can have an influence on photosynthesis, because aside from sunlight, they naturally deprive plants of the resources they require for the process. However, you can make up for this by ensuring your plants are provided with sufficient water, light, and carbon dioxide.

If you’d like to learn more about greenhouses in various environments, check out our list of the best greenhouses for Alabama.