Elementary school science class taught us that plants take carbon dioxide and create the oxygen that we need to live. But do plants actually need air to live?
Plants need air to live, since they need both carbon dioxide and oxygen for photosynthesis and cellular respiration. Photosynthesis uses sunlight, carbon dioxide, and water to create sugars. Cellular respiration breaks down nutrients into energy. Plants absorb oxygen through stomata on their leaves, lenticels on woody stems, and roots.
However, it is important to remember that plants need more than air — they need air circulation.
Plants use up more carbon dioxide during the day than they produce during the night, so if there’s not enough airflow, carbon dioxide levels drop. It becomes harder for the leaves to absorb carbon dioxide through gas exchange. If the plant doesn’t get enough carbon dioxide, it can’t photosynthesize as much, which reduces its growth.
If there’s no air circulation (like if you’re growing houseplants in a cupboard or a pop-up greenhouse), harmful toxins like VOCs can build up.
Air circulation also reduces the risks of fungal diseases, because the plant can dry off more quickly.
Too much air circulation, though, and the plants will close up their stomata, which also reduces how much carbon dioxide they can absorb.
Most houseplants won’t have a problem with air circulation, since you’ve likely put them out in the open and near a window, but if you’re raising plants in closed off areas, then use a small fan aimed horizontally to increase ventilation.
Ready? Let’s begin.
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Do Plants Need Air?
Yes, plants need air, as do all living things. While they don’t have lungs, plants still need to breathe. And this doesn’t mean just air around their leaves – they also need air in the soil.
Plants breathe through stomata on the underside of their leaves, through perforated pores called lenticels on woody stems (those are the streaks on tree bark), and through their roots.
Plants use carbon dioxide and oxygen for two things: photosynthesis and cellular respiration.
Photosynthesis uses sunlight, water, and carbon dioxide to create sugars (glucose). Oxygen and chlorophyll (green pigment) are byproducts of the photosynthesis process.
Plants use the resulting sugars for a ton of purposes, from triggering the transition from a juvenile form to an adult one, regulating a plant’s time cycles, transpiration (water evaporating from the plant), and cellular respiration. Plants can also store sugars in their roots or tubers for later use.
While it’s well-known that plants breathe in carbon dioxide (and breathe out healthy oxygen for us), they still need oxygen too for cellular respiration. During the day, plants keep a bit of the oxygen from photosynthesis for this, but at night, they actually absorb oxygen and release small amounts of carbon dioxide.
But don’t worry. Unlike what a certain myth claims, the amount of oxygen they absorb is so small that it doesn’t make a difference, and so you can safely sleep in a room full of houseplants.
Cellular respiration (or aerobic respiration) is the process of breaking down the sugars created through photosynthesis into energy (adenosine triphosphate or ATP, if you want to get technical) and carbon dioxide. This energy is used for pretty much any process that needs energy, including the metabolic processes that uptake water and plant nutrients.
In other words, plants need carbon dioxide to create the sugars that oxygen turns into energy.
Do Plants Need Air At The Roots?
Yes, plants need air at the roots. Roots need to absorb oxygen through the fine hairs on the root’s tips to live and perform many of their functions, like uptaking water and nutrients.
Without enough oxygen, roots will struggle to grow or will even die off. Less roots means the plant can’t reach as much water or nutrients, and the plant itself is less stable. Eventually, the plant will die.
Roots get oxygen through pore space (porosity), the space between mineral particles and organic matter. This space is filled with air and is where water flows through.
Sandy soil has bigger pore spaces than silt or clay, and that’s why sandy soil dries out so fast. Clay soil has the smallest pore spaces, which is why clay soil struggles the most with flooding and compaction. As a mixture of sandy, silt, and clay, loam soil has the best porosity for gardening.
Organic matter (like compost) can increase or decrease porosity depending on the soil texture, making sandy soil hang onto moisture longer while allowing clay to dry out. 5% organic matter is ideal.
Houseplants are especially prone to compaction, as potting soil breaks down over time. If you haven’t repotted your plant in a while, repot the plant to loosen the potting soil around the roots. You can also gently aerate the top layer of soil with a fork. (More on this below.)
Beneficial microbes in the soil also need air to survive, and they give plants several advantages.
Microorganisms like mycorrhizal fungi create a symbiotic relationship with the plant roots and act like extensions of the roots (reaching more water and nutrients) in exchange for sugar. They also increase resistance to pests and disease, so you end up with a healthier plant.
Microorganisms like entomopathogenic nematodes feed on certain pests. For example, Steinemera feltiae nematodes kill fungus gnat larvae.
Some harmful microorganisms, like Pythium root rot and Phytophthora root and crown rot, take advantage of anaerobic conditions (anaerobic meaning without air), so soil aeration helps prevent these fungal diseases.
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Can Seeds Germinate Without Air?
Seeds contain most of what they need to grow between the time that they germinate and sprout a leaf for photosynthesis. But they can’t access those internal stores of carbohydrates and proteins without oxygen to metabolize them. If the seeds are submerged in water too long or in compressed or waterlogged soil, they can’t access enough oxygen to metabolize their food.
And while technically water contains oxygen, it doesn’t contain nearly enough oxygen to compensate.
However, seeds need water to germinate. Water activates the seed’s enzymes, so the seed releases energy from its food stores.
Water also builds pressure in the embryo’s cells, so the seed expands and breaks the seed coating. This is why pre-soaking seeds (for 4 to 8 hours) that are difficult to germinate works – it softens the shell, so that the seed can immediately start on the next step once they get access to air.
Can Plants Grow Without Air?
No, plants cannot grow without air. They need access to carbon dioxide and oxygen for both photosynthesis and use cellular respiration. Basically, without air, they can’t eat or breathe. Under those conditions, anything living will die.
What Happens If A Plant Does Not Get Air?
If a plant doesn’t get air, it will struggle to grow and eventually die. Plant cells need oxygen to live.
If a plant can’t air through its roots, whether through compaction or overwatering, the roots will die. If enough roots die, the plant won’t be able to take up enough water for photosynthesis or enough oxygen for cellular respiration.
The plant will struggle and stop growing. If the soil is waterlogged, the anaerobic conditions will encourage harmful microorganisms that produce toxins that will damage the plant. Anaerobic soil smells unpleasantly like eggs.
Dust and debris on the leaves make it harder for plants to get enough air through their leaves, and also blocks sunlight. So yes, you do actually need to dust your plants every once in a while.
Stagnant air can also prove damaging, as mentioned above. Plants need air circulation.
If you put a plant in a place that gets little to no ventilation, then the carbon dioxide stores will eventually deplete while toxic gasses build up. These toxic gasses will cause damage to or even kill foliage.
But unless you’re growing houseplants or seedlings in a cabinet, a closet, or a greenhouse tent, you won’t need to worry about stagnation. We tend to place houseplants out in the open near windows where they get plenty of ventilation.
Just don’t clump up your plants too much. If you are growing in a confined space, add a fan to circulate air and open it up every so often to refresh the air supply. Even terrariums should be ventilated every so often.
How To Aerate Compacted Soil In Houseplants?
There are two things that you can do to aerate compacted potting mix: aerate or repot.
If your potting mix is just starting to compact, then you can quickly aerate the top half-inch of the soil using a fork. Always work from the outer rim to the center, and be careful not to poke through the roots or damage the stem.
If you haven’t repotted in a couple years, the soil is severely compacted, and/or water isn’t absorbing into the soil, then it’s time to repot.
To repot:
- Select a pot that’s no more than 2 inches larger than its current pot (1 inch is perfect). Sterilize it so you don’t accidentally pass on any pathogens.
- Use a quality potting mix that includes items that aerate your soil, like peat moss, vermiculite, and perlite. Compost also increases soil aeration. Don’t use garden soil, as it’s too dense. Poor quality potting mix (like you can find at the dollar store) will cause more problems than the money you save.
- Remove the plant from its old pot. Gently knock off some of the compacted soil.
- If the roots are rootbound (circling), then gently unwind the roots. You can also take a knife or trowel to lightly score up the roots and just pull them away from the roots. Try to avoid damaging the roots as much as possible, as it’ll be harder for your plant to recover from the transplant.
- Place the plant into its new pot and fill in the extra space with moist potting mix. Don’t cover the top of the existing potting mix so that the crown or stem remains exposed.
- Water your plant to help it adjust.
Do Houseplants Purify The Air?
Despite what countless blog articles and articles claim, houseplants do not significantly purify the air. The mixup is understandable.
A 1989 report for NASA stated that alongside activated carbon plant filters, plants could potentially be a solution to indoor air pollution (particularly volatile organic compounds, or VOCs) in hermetically sealed environments, like those inside of spacecraft. And for decades, we took that to mean that plants could significantly purify the air.
Outside of a hermetically sealed room, though, plants can’t help much. To get even close to the same effect, you’d need 10 plants per square foot.
That’s a lot of plants, and, according to Michael Waring, an engineering professor at Drexel University who reanalyzed the studies, it has about the same effect as the typical office ventilation system. So many plants in one place also causes other problems, like increased humidity.
The best way to keep VOCs from building up is to not bring in or use products that release VOCs like composite wood products, vinyl flooring, air fresheners, some cleaning products, and tobacco. Look for low-VOC alternatives and don’t store paints, solvents, adhesives, and caulks.
The second best way is to just crack a window every so often to release pent up gas and pollution. (Unless the air outside is worse than the air inside.)
Depending on the filter, an air purifier will remove pollutants like dust, mold, pet dander, smoke, carbon monoxide, radon, and pesticides.
But that’s not to say that houseplants have no benefit in the home. Interacting with houseplants can improve your mood and reduce stress. Psychological effects transfer to physiological effects. In 2009, researchers showed that viewing houseplants improved the outcome of surgery patients by lowering blood pressure and feelings of pain, anxiety, and fatigue.
We humans are meant to be outdoors and in nature, and while it’s always best to get outside, that’s not always possible for us to get much outdoor time, whether due to smog, wildfire smoke, work hours, or disability. Adding houseplants to your office or to your home is a great alternative.
Conclusion
Like all living beings, plants need air to breathe through their leaves, woody stems, and roots. They need both carbon dioxide and oxygen, with carbon dioxide a key component in photosynthesis (creating sugars), and oxygen a key component in cellular respiration (converting sugars to energy).
While lack of air won’t be a problem for most situations, keep your soil aerated and air circulating for healthier plants.
You can get a summary of vegetable plant care basics with this free app I made.
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