Why is it Bad to Put Rocks at The Bottom of a Plant Pot?

Many people think that putting rocks at the bottom of a plant pot is useful for drainage but this is actually a wrong approach. So, exactly is it bad to put rocks at the bottom of a plant pot?

Putting rocks on the bottom of a plant pot is in most cases not ideal. The rocks will not act as drainage but instead, they take up a lot of space in the plant’s pot, which will cause problems for the plant roots. The excess water that is trapped between the rocks in a pot without drainage holes can cause root rot and disease.

After reading this article, you will understand why it’s bad to put rocks at the bottom of a plant pot and what you can do instead. Let’s find out!

Featured image by: Francis Chung

What Happens When You Add Rocks to a Plant Pot?

A lot of people think that putting rocks at the bottom of a plant pot will help with the drainage of water which makes a healthy plant.

Well, actually this is a big myth because rocks don’t improve drainage. By putting rocks at the bottom of a plant pot, you will restrict the amount of soil that goes into the pot. By restricting the amount of soil, you will automatically make the pot smaller for the plant.

When watering the soil, because there is less soil in the pot, the soil will be wetter. This wet soil can cause problems for the plant’s roots. Soil that is too wet or constantly wet will cause root rot or diseases.

Also, the soil contains vital nutrients for the plant and because there is less soil in the pot, the plant will also have fewer nutrients available. Which is not good for the overall health and growth of the plant.

In fact, when watering a planter without drainage holes and rocks at the bottom – another big problem arises. The problem is that you can’t see how much water is at the bottom of the plant pot. When you give the plant too much water, the soil will become soggy and the roots will rot.

Image by: Melissa Gutierrez

Generally, it is not necessary to put a layer of rocks at the bottom of your plant pot. In other words, your houseplant doesn’t need them to survive. Just placing one rock that covers the drainage hole is enough if you are afraid that the soil will come out of the holes. Have in mind that putting rocks do not improve any condition of the soil; it doesn’t improve support drainage or improve the circulation of air in the soil.

So, you got the answer. It is not necessary.

Rocks Do Not Provide Enough Space for Your Houseplant

Rocks don’t provide much room for your houseplant. Below you can see a picture that I made to make this matter clear. Imagine adding rocks until a quarter of your plant pot is filled with rocks. The roots of your potted plant will not grow into the rocks, so this restricts the plants’ space to grow its roots.

As you can see in the picture below, the right plant pot doesn’t have any rocks at the bottom but only has drainage holes. This way the plant has enough space to grow roots and grow healthy.

This will not kill your plant but it is going to limit the size of your houseplant. It will not grow to the size it was meant for.

The best plant pot for your plants is not too big and not too small. It’s best to place the plant in a pot that is the same size as its growing in. For fast-growing plants, you can choose a pot that is 2-4 inches larger than the plant.

If you like this type of content, also check out: How do Plants Get Their Nitrogen?

Rocks May Cause the Roots of Your Houseplant to Rot

As you know by now, adding rocks will limit the space in your plants’ pots. So, what do you think will happen is you add water to a plant pot with rocks at the bottom? Think about gravity when watering plants. You will need to water your houseplant which you have already filled halfway with a layer of rocks. Where do you think your water will go?

The soil on top of the gravel acts as a sponge, sucking up all the water that you give the plant. So, now there is less soil with the same amount of water, resulting in too much water in the soil. Water is there to just moisten the soil, not make a little swamp in a pot. Because there is a big chance that your soil is too wet too often, the roots can go rot.

Alright, now that you know you don’t need to put a layer of rocks at the bottom of your plant, what instances necessitates the use of rocks in plant pots?

When Can I Use a Pot Without Drainage Holes?

In almost all cases its best to use a pot with drainage holes. But in some cases, you can also use a pot without drainage holes. Check out my other article where I have made a list of unique and beautiful plants that don’t need drainage holes.

If you want to use a pot without drainage holes and you are thinking of adding some rocks at the bottom of your plant pot. You might not want to do this.

The excess amount of water in your pot plant may kill your plant. The next things can happen:

  • Disease & Root Rot – If you’ve ever opened a container with food that you had forgotten about, which had been lying around for too long.you’ve learned firsthand what happens when moisture and organic material are trapped in a space with no airflow. A moldy mess!

    When water can’t go anywhere, it will remain there for a long time if something is not done to drain it away. Perhaps the soil gets waterlogged as time passes by.

    The roots of your plants haven’t gone deep enough into the soil because of the rocks you filled your pot with. It’s like your houseplant is just seated on top of excess water that won’t go anywhere. You know where this is going, right? This promotes root rot which will kill your plant over time.
  • Poor Growth – Water, nutrients, and air move through the soil using capillary action, which is sort of like a straw. If you put your finger on the bottom of a straw, it stops working. When you plug the bottom of a plant pot (by trapping it in a non-draining pot), it stops working, too.

    Therefore it is (in most cases) best to use a pot with drainage holes so that the water, nutrients, and air can move through the potting soil with no trouble.

How Do I Prevent the Soil From Falling Through The Drainage Holes?

Often the drainage holes are small enough that this isn’t a problem. but if you’re worried about soil washing out of the bottom of your pot, you can try a couple of things to make sure that the soil stays in the pot. You can try and place one or more of the following objects in front of the drainage holes before putting in the soil:

  • A coffee filter.
  • A piece of screen.
  • A shard of pottery.
  • A small rock.

Even though you “plug” the drainage holes of your pot with one of the objects mentioned above, the water will always find a way out of the pot because there are still small cracks that water can flow through (unless you use perfectly round stones to plug the holes, which I don’t recommend) and the soil will stay in place.

How Do I Make the Water to Drain Faster Through the Soil Then?

Plant roots don’t like to sit in water all the time (unless it’s an aquatic plant). A lack of drainage will result in an unhealthy and dying plant, acting in time is crucial.

Instead of putting a layer of rock at the bottom of your plant pot. Your plants will thrive better when the soil has better drainage. To help soil drain better, you can use high-quality soil that will have better drainage.

You can also make your soil drain better by mixing the soil with either perlite, well-rotted manure, compost, orchid bark, or peat moss. These things will increase the drainage throughout the whole plant pot.

Also if you are potting a succulent, adding builders’ sand is necessary for the perfect drainage.

What to Fill the Bottom of a Large Pot With to Take Up Some Room

Is your pot too big? This is not ideal, but you can make it work (kinda). You can use rocks instead of potting mix. Rocks are relatively cheaper than potting mix especially if you can get them from your own garden.

You can also put rocks on the bottom of the big plant pot and then insert the plant with the smaller plant pot (preferable with drainage holes) in the big pot. This way the plant will still have drainage and the big pot will be filled (see picture).

However, bear in mind that you may have to leave your plant where you potted it because rocks are too heavy to move around.

BUT…

This will only work if the bigger plant pot has drainage holes in the bottom. Otherwise, this is not ideal because you will create a pool of water at the bottom of the bigger plant pot, which can eventually cause root rot or mold.