Why Is Soil in Containers Said to Drain Poorly Compared to In-Ground Soil?

Soil in the ground acts differently because it’s usually a mix of dense inorganic materials like sand, silt, and clay, with organic matter, which helps manage moisture levels. In contrast, potting mixes tend to be lighter and contain things like peat and perlite. These materials are designed specifically to improve drainage in confined spaces. Also, anything too dense can restrict airflow around the roots, making it harder for plants to thrive. You really have to keep mixing it up in containers to avoid issues.

The main reason soil in containers can drain poorly is that once it gets too compacted, the water has a harder time moving through. In the ground, soil can spread out and water can evaporate more freely due to the larger surface area. Plus, the natural organisms in the soil help aerate it and improve drainage—things that just don’t happen as easily in a pot. If you have clay-heavy soil in a pot, for instance, it may just sit there, leading to root rot since there's limited evaporation. So, while soil can certainly retain moisture in the ground too, it's generally in a much healthier state overall due to those factors.

I've heard the argument that soil in containers shouldn't be used because it leads to problems, but who even says that? It seems like it's all about the type of soil you’re using. Most potting mixes should be designed to counteract those drainage issues, unlike just any dirt you’d dig up from your yard.