well drained potting soil

What does well-drained potting soil mean?

Did you ever wonder what the term well-drained soil means?  Every time I look to see what type of soil is recommended for a plant, I see the term well-drained soil.  What does well-drained potting soil mean?  Let’s find out.

well drained potting soil

Let’s take a minute to remember what potting soil is.

This is simply the medium in which you grow plants.

For this discussion, the term potting soil and the potting mixture will be interchangeable.

Potting soil is often a combination of organic and non-organic materials like peat, Vermiculite, perlite, and compost.

A great potting soil will be light and fluffy, and it will include a material that will hold some water and stay airy.  Both air and water in the right amount are essential for healthy root growth.

According to the University of Vermont, the right consistency in container gardening is 50/50 air to the material mixture.

What potting soil is not

Potting soil is NOT dirt.  Although it is tempting to use dirt from outside to fill your containers, don’t!  Putting dirt into your potting will defiantly NOT be well-drained potting soil.

Potting soil is much lighter and airier than even healthy garden soil.  Garden soil will likely compact in a container.

Why is well-drained potting soil so important?

When you grow plants in containers, the soil is where the plant gets the things they need to grow.  The health of the soil will be a huge factor in determining the health of your plant.

What your plant’s roots need

Your plant’s roots need nutrients, air, and water to grow.

When we talk about well-drained, we are talking about controlling the air and water that your plants need.

well drained potting soil

Your plant can be drowned.

Believe it or not, you plant roots breath.  They need a small amount of air in the spacing between the soil molecules to breathe.  Without these small spaces, your plant will be drowned and die.

That is why the “light and fluffy” component is important.  This type of density allows for good air.

If the soil is too dense, watering will cause the potting soil to become muddy. The mud/water will fill the air pockets.

Other problems with poor draining potting soil

Plants that are growing in muddy soil can also develop root problems.  Root rot and bad bacteria can be caused by overwatering.

Salts can build up in the soil, and these salts can damage the root system. Watering with a good drainage rate will help wash these salts away.

Dry soil is also trouble.

Plants do need water, so you can not sacrifice watering to ensure air.  Most plants need a light, consistent amount of water to thrive. The amount and frequency of watering will depend greatly on many facts; type of plant, type of container, the temperature outside, etc.

A test to tell if your potting soil is well drained

Outside gardeners have a pretty standard test to tell if the garden soil is well-draining.

  • Dig a hole about 12″x12″x12″
  • Fill the hole with water and let drain
  • Fill the hole a 2nd time
  • Keep track of the drainage rate the 2nd time
  • The water level should drop an inch an hour
  • If this happens, you have well-drained soil

Test for container potting soil

Water your container well, at least until the water comes out of the holes

  • wait a full day
  • Feel the soil, including deep in the pot
  • The soil should not be muddy and have a consistent moisture level throughout

It is best to test your potting soil in the container and the location of your future plant.

What about self-watering planters?

Self-watering planters or planters that water from the bottom up should have the same well-drained soil.  Your roots will still need a good air mixture and not dense or muddy soil.

Your self-watering planters still need to be watered from the top regularly to help wash away harmful salts that can build up in the soil.

Do rocks on the bottom of a container help with drainage?

well drained potting soil

For years I was taught to put small rocks or clay pieces on the bottom of a pot before planting, and this is supposed to help drainage.

But the opposite is true.  Water molecules form a bond that will create a barrier whenever the molecules reach a different material, which will slow down the drainage.

What if your container has no drain holes?

If you can’t make any, then rocks on the bottom will allow for some space for excess water
to go.  Be very careful with these containers.  It is hard to regulate water without holes.

I hope that you found this information helpful.  Please like, share, and comment.  I really appreciate it!

And please check out How to fill large flower pots and  How to grow citrus in containers.


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