Can You Mix Perlite With Potting Soil? (Explained)

by Alex Kountry
Updated on

Mixing soil with compost has become a norm amongst gardeners. However, compost is not the only thing that can be mixed with soil to improve the growth of plants.

Have you ever bought potted plants or vegetable starters, and wondered what those tiny white lumps are?

Well, That’s perlite, this could lead to further questions such as “Why are they found in the soil?”

Well, perlite is nothing close to fertilizers, they aren’t put in the soil to aid plants’ growth and they aren’t a must for all types of soil.

However, can they be mixed with garden soil? Let’s find out

Can You Mix Perlite With Garden Soil

Can You Mix Perlite With Potting Soil

Yes, Perlite can be mixed with garden soil. Perlite can be used everywhere, in any kind of soil.

It is excellent both mixed in and sprinkled on top of propagation beds and seed starting containers.

Unlike popular opinion perlite is not a fertilizer, it has no nutritional value to both plants and microbes in the soil.

However, perlite helps in keeping the soil structure loose and light. It also helps to hold air in the soil, keeping the plants from suffocating.

This makes it quite essential to be added to the soil.

This article contains amazing facts about perlite. Continue reading to find out more;

What Is Perlite And Does It Have Any Advantage

Perlite is a white granular material that is lightweight. It is a mineral that helps to improve soil structure by providing drainage and aeration.

This is a good thing because controlling water logging in your soil is an important factor in preventing root rot and fungal diseases in plants.

The following ingredients are found in perlite:

  • Silicon dioxide
  • Aluminum oxide
  • Sodium oxide
  • Potassium oxide
  • Iron oxide
  • Magnesium oxide
  • Calcium oxide
  • 3-5 percent of water comprises 70-75 percent of the total

Perlite comes in a form of volcanic glass which is formed when volcanic obsidian glass is saturated with water over a long time.

Perlite is a natural filtration system that allows excess water to drain away while retaining a small amount of moisture and catching nutrients that plants require to grow.

This is particularly evident in raised beds and container gardens, however, it also applies to conventional gardens.

Let’s look at some amazing advantages of perlite;

  • Perlite is physically stable and it retains its shape, even when inserted into the soil.
  • Perlite doesn’t decompose, and can be reused hence it is not expensive. You can use it for years and when you’re going to reuse it, you should clean and sterilize them first.

It is best used for plants in potting mixes such as succulents and house plants, this is because it is not repotted frequently.

  • It has a neutral pH level, which is recommended for plant growth.
  • Perlite does not contain toxic chemicals or additives, which makes it totally safe for your soil.
  • Perlite medium is usually sterile because it usually undergoes a heating process. This enables it to be free from fungi and bacteria.
  • Perlite Insulates and minimizes temperature fluctuations.
  • It also provides excellent aeration for plants. Generally, perlite is incredibly porous and contains pockets of space inside for air.

Plants absorb a large percentage of oxygen through the roots, so good aeration is crucial for healthy root development.

The perlite will trap air in the compost and encourage water to drain through.

Proper airflow also supports earthworms, beneficial nematodes, and other good things in the soil food web, which in turn supports plant life. 

Here is an article I wrote on using potting soil in an aquarium

How Much Perlite Do I Add To Soil?

How much perlite you add to the soil is largely dependent on the purpose of the plant.

For a garden, In most cases, it is sufficient to mix the soil with 10 to 20 percent perlite.

In the garden, perlite can be used primarily on soils that are difficult to retain moisture. This includes mainly sandy soils or those that are in areas that are not sufficiently covered by precipitation.

For potting soils, between 5 and 35 percent of perlite is added to the soil.

Many potting soil manufacturers use perlite to ensure better water retention in their soil and to make potting soil looser in the long term. 

The porous surface of the expanded perlite creates space for both air and water, which among other things is beneficial for root growth.

Note that it is very essential to take precautions when adding perlite to the soil.

In addition, ensure you always wear a dust mask when mixing perlite into the soil to avoid inhaling too much of it.

Dust masks are affordable, and they certainly add a professional touch to your work. Always read and follow the instructions on the packaging to get the most out of the dust mask.

Is Perlite Safe For Vegetable Gardens?

Yes, perlite is safe for vegetable gardens. Perlite isn’t poisonous and there is no way they’re going to add any possible toxins or residues to your soil or vegetables.

Perlite is a good aerator for your vegetables, perlite also prevents plant suffocation and root rotting. It has neutral pH levels which your vegetable will most likely prefer.

Is Perlite Good For Tomato Plants?

Tomato plants need an adequate supply of water and cannot thrive on totally dry soil. However, tomato roots do not like sitting on waterlogged soil either.

With perlite, tomato plants can achieve the most suitable soil they require, hence making perlite good for tomato these plants.

Tomatoes grow in most types of soil except on heavy clayey soils which greatly obstruct the root growth.

However, the flavor of tomatoes varies greatly depending on the soil you have planted them in and what you are feeding the plants.

Interestingly, perlite has a positive effect on the soil of tomatoes, which in turn gives the vegetable an exceptional taste.

Also check out this article I wrote on mixing mulch with potting soil

How To Use Perlite For Cuttings?

Perlite aids water retention in compost, which can help your cuttings take root more easily. It’s also useful for propagating plant cuttings.

You can root your cutting in a tiny jar filled with moistened perlite instead of just water.

Here are the steps require use per tile for cutting;

  • First you need compost that is specifically designed for cuttings. It needs to be a finer texture with lower nutrient content than general use multi-purpose compost. 
  • The perlite should be mixed in equal proportion. Mix in perlite at a ratio of 50:50, fill the pots, water thoroughly, and then allow the compost mix to drain for several hours before inserting your cuttings.

Cuttings can also be rooted in perlite on their own, here’s how to achieve that; 

  • Moisten the perlite and fill a polythene bag around a third full. 
  • Prepare softwood or semi-ripe cuttings by cutting just below a leaf joint. Afterward, remove the leaves on the lower half to two-thirds of the cutting.
  • Insert the bare lower part of the shoot into the perlite, fill the bag with air and seal the top. After several weeks, roots should start to form. Once roots are well developed, the cutting can be taken out and potted up in the compost.


Perlite is a good mix for garden soil. They are not fertilizers and they aren’t meant for the nutritional benefits of plants as well.

Perlite however functions as a natural filtration system that allows excess water to drain away while retaining a small amount of moisture and catching nutrients that plants require to grow.

Perlite isn’t poisonous to plants in anyway, they are super safe for your plants. Plants such as tomatoes and vegetables do well with a perlite mixed soil. 

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About the author

Alex Kountry

Alex Kountry is the founder of HayFarmGuy and has been a backyard farmer for over 10 years. Since then he has decided to write helpful articles that will help you become a better backyard farmer and know what to do. He also loves to play tennis and read books


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