Best Soil for Indoor Plants and How to Mix Your Potting Soil

Today you’ll find so many different types of packaged soil in store, it is hard to figure out what soil you need or should use for your indoor plants.

Can you buy the same type of soil for plants on your balcony as for your indoor plants? Could you just dig out some soil from your backyard and use it for potting your houseplants? Not quite! But getting the right soil ready for your indoor plants is not as difficult as it may seem!

The best soil for the majority of indoor plants contains a balanced mix of humus and well-draining matter such as coconut coir, shredded bark, pumice, perlite, or sand. Indoor potting soil provides adequate drainage, moisture regulation, aeration, nutrient retention as well as root stability.

In this post, I’ll go into what the difference between soil and potting mix is, what soil or mix is good for your indoor plants, and also how you can easily make your own potting soil by blending a couple of ingredients together! You’ll see that providing your plants with good soil to grow in is not that much effort after all!

Table of Contents

Can You Use Any Soil for Indoor Plants?

Use Potting Soil or Mix That Is Labeled as Suitable for Indoor Plants

First, we have to sort out the terms “potting soil” and “potting mix”. Technically speaking, potting soil contains humus (=compost or dirt) while a potting mix comes without humus. This is why many potting mixes are labeled as “soilless” meaning they do not contain soil in the sense of dirt or earth.

In practice though, this separation of “potting soil” and “potting mix” is oftentimes not adhered to and you will find many stores selling potting soils that contain more ingredients than humus and potting mixes that contain humus as well.

Instead of getting confused by the terms potting soil and mix, what you want to look out for is whether the soil/mix is meant for potted indoor plants and not for gardening or the outdoors. Except for specific plants like succulents and cacti or orchids, most of your regular indoor plants will do well with any type of indoor potting soil/mix.

Rule of Thumb: For indoor plants, any potting soil or mix that is labeled as suitable for indoor plants will do for most houseplants you have. The only type of soil you shouldn’t use indoors is those that are made for the outdoors and outdoor gardening.

Is It OK to Use Garden Soil for Indoor Plants?

Try to refrain from using any type of soil from the outdoors for your potted indoor plants. You might wonder why because you have plenty of available soil out in your backyard and don’t want to spend money on buying soil.

Well, the soil in your garden contains lots of bugs, bacteria, and fungi that can potentially harm your indoor plants because they are not used to those kinds of pests. In addition, garden soil generally is quite heavy as it is primarily made of clay, humus, sand, and silt. Heavy and dense soil like in our gardens tends to get clogged up and compacted when moist or hardened out completely when dry.

All of these characteristics are not what you want for your potted indoor plants. In pots, it is especially important to create an airy and rather loose environment for your plant’s roots.

Why do plant roots need air? Because they breathe oxygen just like we do! To ensure your plant roots get enough oxygen, not just the choice of soil matters but also how much drainage you create in the pot. Find out more about why plants need drainage and how to create drainage in any type of pot in my post linked here!

What Qualities Does Good Soil For Indoor Plants Have?

The climate we create in our plant pots should best mimic the conditions the plant would find in its natural habitat. In nature, the soil regulates itself and a plant only grows where conditions are favorable. In a pot, we have to create the regulation and good conditions ourselves in an attempt to reproduce the natural cycles.

The main functions the soil has for indoor plants are:

Aeration: porosity of the soil is important: space between the soil particles
Moisture regulation: Most plants do not like to sit in water permanently but long periods of drought are not beneficial either. The soil, therefore, plays a crucial role in retaining just the proper amount of moisture needed, not more but not less.
Water flow: The soil should be composed in a way that provides a good and constant water flow through the pot. The water should be able to find its way down and out of the pot, just like it is pulled by gravity. Saturation zones created by clogged-up soil can hinder that flow.
Nutrient retention: After the first few weeks, the soil itself will mostly be empty of nutrients. Its nutrients are then replaced by using fertilizer when watering the plants. By retaining an adequate amount of moisture, the soil also retains the adequate amount of nutrients given. It prevents the nutrients from being washed out too fast.
Root stability and environment: The soil gives appropriate support and stability to the plant’s root system which helps the plant grow tall. Also, roots generally prefer to grow in the dark and the soil also allows for a more stable temperature around the roots.
Resisting compaction: A good soil mix will stay airy and loose for a long time, preventing compaction around the roots which would lead to a lack of oxygen.
Providing a beneficial microbiome: Last but not least, soil comes with a beneficial microbiome of healthy bacteria that can boost a plant’s resilience.

Tip: Even though potting in soil has many benefits, it is also possible and sometimes just as beneficial to grow plants in just water. Having plant vases around also simply looks great! Read more in my post on how to grow plants in water and what tips you need to keep in mind to do it right!

What is the Best Multipurpose Soil Mix for Indoor Plants?

The key factor you should look out for in a multipurpose soil mix for indoor plants is that it has a balanced composition of humus and other well-draining matter. Instead of falling for any labels on the package, check the ingredients and see what really is in it!

Rule of Thumb: If the soil package contains humus/compost as well as well-draining matter, then it is an adequate potting mix for the majority of indoor plants.

Apart from the composition of the soil mix, I also recommend buying organic soil. With “organic” I don’t mean soil that is only made up of organic components (for example perlite or pumice count as inorganic components). Rather, I mean organic soil that is free of synthetic or chemical fertilizers and components.

Organic soil packages usually list all the ingredients comprised whereas non-organic products often do not mention what is actually in it. Always go for packages that mention all the ingredients!

Doing some further research for this blog post, I read that some brands add styrofoam for better drainage or that humus is laced with sewage dumps. When reading that sort of stuff, I was very glad to always have opted for organic and sustainable soil mixes! It’s just better for your plants and the planet!

Tip: In some countries, there are no regulations in force about organic standards for soil such as in the US. If you are in the US, a safe label to look out for when buying soil is if it is “OMRI Listed”. This means the product adheres to USDA organic farming standards.

Some garden centers recommend using only soilless potting mixes (= with no humus) to lower the risk of pests for your indoor plants. Pests and bugs mainly need humus to lay their eggs in. Leaving out the soil makes it harder for them to reproduce.

But honestly, even though some articles make it sound like soil is THE pest-infested material, that’s not what it is like at all. Soil does not immediately attract all kinds of diseases. On the other hand, it also has many benefits for plants such as root stability and temperature regulation as well as many beneficial bacteria. A healthy microbiome can boost a plant’s resilience and strength.

Personally, prefer to pot my plants in a mix of soil and well-draining matter. You can do nothing wrong by buying good quality organic multipurpose potting soil for indoor plants and amending it with one or two extra well-draining materials.

If you prefer though, you can put your plants in a mix without humus, or even in just water. Want to know more about what benefits soil has or how you could grow them without soil such as in just water, check out my post on the pros and cons of growing houseplants in soil vs. water.

How to Mix Your Own Potting Soil for Your Indoor Plants

Add One or Two Drainage Materials to Your Store-Bought Potting Soil

Once you have bought your organic multipurpose soil package from the store, it is very easy to improve its qualities even further by adding one or two more ingredients yourself for extra drainage.

What you want to create for your indoor plants is a soil mix that has very good drainage with lots of air pockets while at the same time, it is able to retain enough moisture and nutrients. How do you achieve this: By mixing the denser and more compact humus with slightly coarser materials generally referred to as well-draining matter.

For most plants, two great rules of thumb for mixing soil and drainage matter are:

Mix 1/2 humus (potting soil) with 1/2 drainage matter (such as sand, coconut coir, shredded bark, etc.).
For more water-loving plants (such as those of tropical climates), opt for a little more humus in the mix. For more arid or temperate plants, opt for a little more drainage matter.

With the 50-50 rule of humus and drainage matter, you can’t go wrong. After all, what makes a plant thrive in the end is not just the soil but mainly how you water it in the long run. You can have the best soil and your plant still dies if you overwater it.

How to know if you are overwatering your plants? Watering your houseplants correctly is not as easy as it seems. But with a handful of basic tips, you can learn how to do it right easily. Find out how to water your plants the right way in my post linked here!

What Are Good Drainage Materials to Add to the Soil?

Now, what materials can you add to your potting soil to increase its drainage capacities? Here’s a list of all the materials commonly used for that:

Perlite: This is a type of volcanic glass that has been expanded under extreme temperatures. Through the expansion, it gains a highly porous surface which makes it perfect for drainage in a soil mix.
Pumice: This is a material made of very small and light volcanic rocks. As you probably know, volcanic rock also has an extremely porous surface. Contrary to perlite, pumice does not need to be heated up which makes it a more sustainable alternative.
Vermiculite: This is similar to perlite, but it has been found to contain traces of asbestos. I recommend NOT using it! I just put it on this list here because it is still present in many soil mixes you can buy, so it’s good to know why not to buy it.
Expanded clay: An affordable option you can find in any garden center.
Shredded bark or wood: Mainly pine or fir bark is used such as what you find in orchid mixes. Bark can be grown and harvested naturally and is renewable, hence this makes for a good sustainable option.
Coconut coir: This is made of shredded coconut husks. It is sustainable in the sense that it is a renewable material but on the other hand it usually has to be transported quite far from where it is produced.
Sand: Sand is more common for succulent and cacti mix, though it helps for drainage for any potting mix. Tip: You can just buy regular bird sand.
Horticultural/organic charcoal: Charcoal soaks up excess moisture and is said to have anti-bacterial properties that help filter out harmful substances from the soil.
Rice hulls: This is also a waste product that can be reused for a new purpose in plant pots!
Sphagnum peat moss: Peat moss is harvested from peat bogs in Northern countries. As peat moss takes a very long time to regenerate, this is one of the ingredients you should avoid buying. Even though it has great moisture retention properties, it is just not environmentally justifiable anymore to use peat moss.

Personally, I like to amend my potting soil with a mix of shredded bark and sand to minimize my carbon footprint. These are more sustainable options and you can also find them in any garden center. Also, bark and sand work for varying potting mixes: For succulents and cacti, I add more sand, and for other plants more bark and humus.

Left to right: Soil with more sand and soil with more bark added to it

After Potting Your Plants: Tips to Keep in Mind

When you are done repotting your plants, you might have some soil left. To store left-over potting soil, either close the bag air-tight or put it in a closed container. Stored like this, it remains good to use for a very long time. Also, you might want to note down the ingredients on the bag to make sure you don’t forget what’s in it.

Keep an eye on the soil and the plant after repotting it. If you notice any bugs or flies appearing, there may have been eggs in the soil you bought. This can happen sometimes even with good-quality soil. If you notice anything, make sure to do something about it soon. There are plenty of organic or natural treatments against most bugs. Also, it can help to put a layer of pebbles or shells on top of the soil.

Another tip to keep in mind is that the nutrients in fresh soil generally last for about six weeks. So, for the first six weeks, no fertilizer is needed. After six weeks, start using fertilizer every second week in the summertime while giving your plants some rest in wintertime.

With these last tips, you are more than well prepared to make your own potting soil mix and repot your plants! Enjoy the process!