The problem Once you have graduated from novice plant parent, how can you take your level of care to the next level, helping your houseplant not only survive but thrive? Is activated charcoal the answer? You will find it listed in terrarium recipes and soil amendments. It promises to filter toxins, absorb odours, prevent mould and keep roots healthy. The bag looks purposeful, and the price suggests it is doing something important. The question is whether any of that holds up in an ordinary pot on an ordinary windowsill. The hack Activated charcoal works by adsorption, trapping impurities on its porous surface. In a closed terrarium or bottle garden, where water recycles and there is no drainage, a charcoal layer can slow the buildup of gases and bacteria. But does that translate to standard houseplant pots? The method Add a thin layer of activated charcoal at the base of your pot before filling with compost. You can find it in garden centres, houseplant shops or online. A little goes a long way.…