Should You Use Soil Cover For Potted Plants? (and Mistakes To Avoid)


Are you considering using soil cover (also called mulches) for your indoor plants? Perhaps after seeing other gardeners using it outdoors, you wondered if it would be beneficial for your potted plants.

Using soil covers, often called mulches, for indoor plants is beneficial by reducing the incidence of diseases, retaining moisture, reducing pests, and even providing nutrients. However, the impact on indoor plants and herbs growth varies greatly depending on the chosen type of soil cover.

When and how you should use mulches? Do you want to avoid some easy mistakes in applying them? Keep reading for more!

Soil Cover Benefits for Indoor Plants and Herbs

As the word suggests, the soil cover is a material placed on top of the soil where your plants grow. Among the benefits of using soil cover, I would mention:

  1. Reduce the incidence of disease by stopping soil from splashing up onto the leaves of your plants.
  2. Keep moisture: This is important for those herbs that do not tolerate drought;
  3. Avoid parasites: The soil cover makes it more difficult for pests to access the soil
  4. Nutrients: many soil cover (not all of them) release (some) nutrients over time that will be beneficial for your potted plants;
  5. Soil temperature: like a “blanket” soil cover can limit the temperature swings in the soil due to change in the environmental temperature (like you turning off the heating when you go to work in winter).
  6. Improve drainage: by increasing the soil aeration when (over time and watering), the soil cover particles tend to become part of the potting mix (like those of sharp sand). Such soil cover can be particularly useful for plants which require free-draining conditions, like Mediterranean herbs, or succulents, for example;
  7. Esthetic: using some pretty soil cover such as stones and pebbles, can give a great touch to your indoor herbs collection.

However, it is not all perfect. Among the disadvantages of soil cover for indoor plants it worth mentioning:

  • Lack of nutrients: some soil cover (those defined as “inert” or not organic) do nothing to add fertility for your plants. But they may be more appealing for those who value a clean, tidy and attractive appearance.

    Is this a problem for you? It should not. Indeed, I do recommend to not rely on mulch to fertilize your soil. You should use proper fertilizer, as discussed in this detailed article.
  • Ingestion: If you go for a visually appealing soil cover (pebbles, or glass beads, for example), you should be careful in case of young children or pets around as they can easily swallow such small pieces of material (a few millimeters).

    This can be a severe problem if you have pets or toddlers around. Of course, a solution can be to keep them away, but we know how kids and pets can be “ingenious” to find new ways to access pots. Have a look at how to set up your indoor garden to be cat-proof. You can use similar strategies for your dog.

What Type of Soil Cover Exists?

Choosing the right type of soil cover for your plant is important. What you need to know is that there are two main types of soil covers.

  1. Organic: this is an organic material, hence over time it will “disappear” (degrade) and need to be replaced;
  2. Not organic (Inert): these types of cover(s) essentially stay the same (do not degrade) over the years as they do not decay and are not affected by any biological process;

Here is my take away

It is also a good idea to look carefully at a soil cover you are considering to make sure it is eco-friendly and comes from a sustainable source.

Organic Mulch

Organic mulch is a layer of organic material that will slowly break down and decompose over time to add fertility to your containers. Mulch can be compost, processed wood, manure, seaweed, stones, and a few more.

The benefit of such materials is that they can be used to maintain the level of nutrients in the soil over time – keeping your indoor plants and herbs growing strong and happy.

Remember, though, that organic mulches should be replenished once or twice a year as they break down over time.

Not-Organic Mulch

When I mention inert mulches, I refer to those materials that are often plastic or mineral derivatives. There are countless of them out there, such as decorative sand, horticultural gravel, or decorative glass beads.

They usually come in bags big enough to cover a few potted plants. Unlike organic mulches, these soil covers will not break down and can last years and years.

Remember, like organic mulches; however, inert soil covers will also help reduce moisture loss from the soil/growing medium.

DIY Soil Cover and More

Organic mulches can be an option, especially considering that with a bit of an effort, you can create them at home. As mentioned above, you can use compost or leaf mold. And both of these could potentially be made by you.

You may also be able to collect fall leaves from your neighborhood to make your own leaf mold at home. You can also raid kitchen cupboards to find a range of plant-based materials to use.

A second, still eco-friendly option, is to use plants! Indeed, certain plants might cover your potting soil entirely. In other cases, the soil cover may be a secondary plant – used to give soil cover around the main specimen.

Moss is one potential option. It can look good, and also help retain moisture and increase humidity ad discussed in this study. However, it will only be suitable for plants that like wet soil conditions, whilst for others, dry soil loving plants might do more harm than good.

Other Options (and 3 Things To Remember)

Soil cover can be obtained with countless different materials. However, independently from what you choose here two

  1. Choose lightweight mulches that can easily be incorporated around the edges of plants. Overly heavy mulches (like rocks), or mulches that are too wet or too dry (wood chipping), could prevent water and oxygen reaching plant roots. The weight, especially in planted potted, might, over time, press the soil reducing the air pockets within it. This makes it difficult for your potted plant roots to breathe.
  2. Avoid mulches from unknown sources. Compost may seem harmless and can be beneficial, for example. But unregulated composts could contain harmful substances if from an unregulated source, as discussed by the University of Oregon.
  3. Avoid adding anything contaminated with pesticides or other harmful substances.

If you are looking for organic mulch, I would go for shredded bark like this one on Amazon. Good quality and organic origins.

Another organic friend option is to add another plant to cover the soil around a central specimen, consider companion plants. For example, basil, chives, and other herbs are said to be beneficial when planted around a tomato plant (yes, you can grow tomato indoor, check the video below on YouTube). A nitrogen-hungry plant may benefit from the inclusion of a nitrogen-fixing plant like clover around the edges of the container.

Here a surprise

Plants are not the only living things that will benefit from the inclusion of moss in indoor containers. Moss has also been shown to be better than other plants are removing particulates/ air pollution from the surroundings.

The Three Best Soil Covers For Indoor Plants and Herbs

In my opinion, the easiest way is to use those not-organic mulches that have the advantage to be light, inert, good looking indoor, cheap, long-lasting, and have an overall “neat” look.

I usually go for decorative sand (a good brand here on Amazon), horticultural gravel (this one on Amazon is quite good), or decorative glass beads (here how they look like).

There are plenty of beautiful options to choose from!

How To Apply Mulches on Indoor Plants (What to Avoid)

I add this section after checking the picture that some of my readers (Anna, this is for you) send me about their soil covers. More precisely, when applying mulch on potted plants you should avoid:

  1. Using outdoor mulch
  2. Create a too thick layer
  3. Create a mulch volcano around the stem

Outdoor Mulch

Mulch can be easily found outdoor especially if you are lucky enough to live close to a large park or forest. So why spend a few dollars? Well, in this case, that is money well spent as the outdoor alternative can make you regret it.

Indeed, chances are that you are going to introduce some pathogens or pests using mulches that you find outdoor. Indeed, the variety of insects and biodiversity is so large outdoor that, even if that barks might look “clean”, chances are that there are dozens (if not hundreds) of tiny pests or (under spore form) parasites.

Thick Mulch Layer

The more mulch is not the better. In potted plants I would avoid anything above 1 inch of thickness. Why? Because you can accidentally create a coating that prevents the plant to breathe. Moreover, it thick layers (with empty spaces in between if use bark or any other rough similar material) are the best places for pests to live in.

Mulch Volcano

Accumulating mulch around the stem of the herb is a no-no. Indeed, especially moisture-retaining mulch will slowly rot the stem. Something that definitely you do not want.

When Not To Use Mulches

I would not recommend using any mulch for all indoor plants that do not tolerate overwatering, especially if the mulch has the ability to effectively trap moisture (like bark). Think about basil and rosemary.

This is because chatting with a few of my readers and reading around on gardening forums, I noticed the same pattern. Indoor basil, more often than not, dies because of root rot due to too much love (translated into water).

Indeed, if you think of it, any herb that lives in your house or apartment will receive way less light, and it will be exposed to a lower temperature compared to its outdoor counterpart. This implies a lower water consumption than you might think to let the water your generously given to you plant, hanging around for longer (too long). The situation will then get worst with moisture-retaining soil cover.

Further Questions

What is the main purpose of mulch? When used outdoor, preventing weeds and retaining moisture during the growing season (beginning of spring) are the main purposes.

Does mulch contain compost? Mulches do contain compost or other organic material. Moreover, compost is also a type of mulch

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Andrea

A young Italian guy with a passion for growing edible herbs. After moving to the UK 6 years ago in a tiny flat, it was impossible to grow herbs outside. So I start my journey in growing indoor and so I decided to share my knowledge.

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