An old gardening tip, often passed down through generations, suggests lining the bottom of pots with coarse materials like gravel, stones, or broken china to improve drainage. This practice, known as crocking, is often touted as a must-do. However, while it may have been common advice in the past, modern horticultural research has shown that it’s not necessary and can even be counterproductive.

Many people still do it, but according to scientists, crocking doesn’t help drainage at all. In fact, it can hinder it.

Guy Barter, chief horticultural adviser at the Royal Horticultural Society, says a crock is actually likely to worsen drainage by creating a block. It’s better to have a layer of sand underneath soil that will allow water to drain into it and later be sucked up by roots if needed.

Associate Professor and urban horticulturist Linda Chalker-Scott, from Washington State University, states that crocking can lead to waterlogging.

The coarser the underlying material, the more difficult it is for water to move down across the interface and out through the drainage hole.

Basically it’s like having a smaller pot, and you’ll be wasting valuable pot space. You’ll just end up with crowded plants sitting in ‘too wet’ soil.