Pebbles for drainage. Does it work?

There’s a lot of conflicting information out there about whether it’s beneficial to add gravel, rocks, or pebbles at the bottom of pots when repotting plants. So, what’s the real story? Does it actually help?

The idea behind adding rocks or gravel beneath the soil in a pot is to improve drainage, which is believed to prevent water from pooling around the roots and causing root rot. On the surface, this seems logical, and many gardeners have followed this practice for years. But does it really work the way people think?

In reality, adding a layer of gravel under the soil is more of a gardening myth, especially when it comes to container plants. Here’s why: In nature, gravel can indeed assist with soil drainage. The small rocks help keep the soil loose, allowing water to flow between the gaps and filter down. This natural drainage system prevents the roots from sitting in excess water, which is crucial for the plant's health. However, in the confined space of a plant pot, things work a bit differently.

When you place rocks or pebbles at the bottom of a pot, the soil above them will eventually start to sift down into the crevices. Over time, the soil compacts and fills in the gaps between the rocks, creating a solid, almost cement-like layer. Instead of improving drainage, this compacted layer can actually prevent water from moving freely. The water may sit at the bottom of the pot, keeping the soil too wet and increasing the risk of root rot.

Another issue arises if the pot doesn’t have proper drainage holes. Without an exit for excess water, any water that makes its way down to the rocks will have nowhere to go. The water may stagnate at the bottom of the pot, creating a damp environment that’s harmful to the plant’s roots. This can lead to root rot or other moisture-related problems that hinder the plant’s growth and health.

So, what’s the best way to use rocks or pebbles in your potted plants? Instead of placing them inside the pot, they’re best used underneath it. You can place a layer of rocks or pebbles on the drip tray, elevating the pot slightly. This way, when the pot drains excess water, the water in the drip tray doesn’t come into contact with the bottom of the pot, preventing the plant’s roots from being exposed to standing water. It also allows for better airflow around the base of the pot, which further helps keep the roots healthy.

To promote good drainage inside the pot itself, it’s best to use high-quality potting mix designed for the type of plant you’re growing. Many potting mixes contain materials like perlite, vermiculite, or bark, which naturally aid in keeping the soil loose and well-draining.

In short, while adding rocks under the soil in potted plants is a common belief, it’s more of a gardening myth than a helpful practice. For the healthiest plants, focus on using the right soil and ensuring that your pots have proper drainage holes. Save the rocks for decoration or to help with water collection beneath the pot!