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Using Styrofoam in Soil: What It Actually Does and Alternative

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There are plenty of ways to use styrofoam in the garden and sometimes styrofoam can be confused with perlite. Whether it is your veggie garden or container garden, and adding it to soil is not one.

Using styrofoam in soil may seem beneficial but it can cause more harm than good. Styrofoam is a non-biodegradable product and does not benefit the environment. It is often confused with perlite and they both differ greatly when it comes to water retention, aeration, and drainage. 

Improving soil quality is imperative for healthy plant growth and we have outlined what styrofoam will actually do when added to soil as well as how using its “look-alike†perlite will benefit plants.

Is Styrofoam Safe for Plants? 

Perlite in Soil

For years, it has been thought that styrofoam can be used as filler for plant pots due to its long-lasting nature and its potential in improving drainage. 

However, it’s still not clear how styrofoam products decompose in time, given that landfills are already full of non-biodegradable products. Nowadays, Styrofoam is not suggested to add to soil because of its harmful effects on the environment.

According to the National Institute of Health, styrene (of which Styrofoam is made) is enlisted as a cancer-causing substance. However, it is more hazardous to those dealing with it as compared to ones who simply do planting in Styrofoam containers.  

It is considered that Styrofoam isn’t affected by soil or water and takes many years for degradation. While regarding leaching, levels are not high enough to cause issues as it requires temperatures to occur, according to experts. Hence, plants growing in recycled Styrofoam planters are considered safe

But regarding your awareness about possible outcomes of planting in Styrofoam, it’s better to avoid growing edibles and limit yourself to only decorative plants. Proper disposal of recycled foam planters is important. However, disposal by burning must be avoided as it will result in the emission of dangerous toxins.

Can Styrofoam Benefit the Soil? 

Ask a gardener to share some tips with you regarding the use of Styrofoam in their gardens. Definitely, they would be happy to share a few Styrofoam gardening tips with you.

Styrofoam plays a huge importance in gardening in different ways. But there are many myths regarding the use of this material in gardens. Let’s see if Styrofoam provides any benefits to the soil or not. 


Have you ever heard about the improvement of drainage by adding Styrofoam to the bottom of containers? I think you have. For decades, gardeners have used Styrofoam for this purpose but is it really good?

Well, the answer is not really. Adding Styrofoam packing peanuts can do more damage than good to your plants as well as soil. Within foam material, deep plant roots can grow but without proper drainage, they can die in the waterlogged surrounding.

Moreover, Styrofoam provides no nutritional value to the plants because the synthetic material used in Styrofoam peanuts contains no nutrients. Biodegradable packing peanuts provide no advantage in drainage although they are made of natural materials, on the absorption of water, they disintegrate.   


There is a common misunderstanding that white foam-like balls present in potting soil are Styrofoam. These materials are used to keep potting soil loose and aerated but these materials are perlite instead of Styrofoam. It does not absorb moisture but holds it in tiny cavities around the outside. It makes water available to nearby roots efficiently.

Perlite can decompose naturally with time, unlike Styrofoam. Therefore, they don’t cause any threat to the environment. While Styrofoam can’t decompose for millions of years. It may also take on moisture and become waterlogged causing soil compression.

During heavy rains, Styrofoam can slide away into the water body contributing its portion to ocean pollution.

Water retention

Styrofoam, a substitute for perlite, does not aid in water retention in soil. Moreover, adding Styrofoam results in adding plastic to the environment. Ideally, potting mixes should use perlite.  The porous structures on the perlite’s surface holds water, presenting alternate moisture to the roots whenever they need it. 

Perlite reduces the chances of drying of roots as it allows the soil to drain and retain moisture for a longer time. But most of the potting vendors replace perlite with a cheaper substitute that performs the same function but is harmful to the environment. 

What is Perlite


Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated.

Since perlite comes from volcanic glass it is made up of primarily 70 % silica and other elements such as aluminum, potassium, sodium. These elements are also beneficial to plants when added to soil.

Perlite is not Styrofoam, it is actually a low-density industrial product used in construction, horticulture, and materials used to make filters.

Perlite has a slightly polished appearance due to the bubbles with the structure and is oftentimes mistaken for Styrofoam or even eggs in the soil because of how similar they appear. 

The size of the perlite substrate varies by the product sold and is determined at the production facility as demand requires. 

The normal size of perlite is 0–2 mm and 1.5–3.0 mm in diameter.

Coarse grade perlite can range between 3mm to 8mm in diameter

Perlite Properties

Soil Remedial PropertiesNo
pH Ranges7.0 – 7.5
Retains Soil moisture and nutrientsGood
Increases Soil Drainage abilityBest
Weight5 – 8 lbs/CuFt
Size 0 – 8 mm
Contains natural MineralsGood
Approved for organic gardeningYes 
Decomposes over timeNo

You can find a cost-effective mix of perlite and vermiculite for all your potting needs on Amazon. Find it by clicking here.

perlite and vermiculite from amazon

Benefits of using perlite in the garden

Perlite is a highly useful component of gardening for many reasons:

  • It is physically stable and retains its shape
  • It doesn’t decompose
  • It has a neutral pH level
  • It contains no toxic chemicals or additives
  • It’s able to absorb some water while letting the rest of it drain freely.
  • It provides excellent aeration.

Why does Perlite look like Styrofoam? 

Styrofoam vs Perlite

Do you want to know why perlite looks like Styrofoam? So basically, the reason is that perlite is a white lightweight granular material. It is an amorphous glass formed by the hydration of obsidian. 

On heating up to 1,600 degrees Fahrenheit, the glass puffs up like popcorn, resembling Styrofoam in appearance. Therefore, perlite is sometimes known as “volcanic popcorn”.

Being a raw material, Perlite contains water that is trapped by the rapid cooling of lava. When heat is applied, the moisture evaporates explosively. 

Styrofoam vs. Perlite: Are They the Same? 

In order to move on to more details, let me clarify whether Styrofoam and Perlite are the same or different. 

Well, Perlite, a kind of volcanic glass containing high water content is excellent for enhancing soil used for plants grown in containers and for starting seedlings for soil or soilless medium. It provides a healthier root system by improving drainage and aeration.

But buying enough Perlite for plant growing containers is so costly, therefore its substitute is used, is Styrofoam. Styrofoam is an expanded polystyrene foam used in plant containers. These foam plant containers are lightweight and easily movable. 

These Styrofoam containers are inexpensive compared to Perlite and provide extra insulation in winters.

Can you Plant in a Styrofoam Pot? 

Yes, you can. For better drainage, dig some holes in the bottom of the container to prevent the plants from rotting. In the case of shallow-rooted plants, add a few inches of Styrofoam peanuts at the bottom of the planter.

A Styrofoam container can hold more potting mix than the plant needs. Add commercial potting mix along with compost and well-rotted manure in a container up to the height of 2.5cm. To ease the drainage, elevate the container with the help of bricks from an inch or two. 

Place your container where plants can get optimum sunlight. Carefully, put your plants in the potting mix. During hot days, plenty of water is required by the plants in Styrofoam containers. In that case, a layer of mulch helps in keeping the potting mix moist and cool. 

The Takeaway: 

Styrofoam has been used for decades in the filling of planters because of its effectiveness in improving drainage.  Now, many landfills are overloaded with non-biodegradable products due to which Styrofoam breaks down. 

However, because of hazardous damages that Styrofoam can cause to the environment, it is not recommended for adding to soil. 

Although perlite is great for the potting mix, it is an expensive product and can help recover compacted soil where plants can’t grow. 

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