What a good mix actually does

After this you can tell why an airy, free-draining mix keeps roots healthy.

Good potting mix is a balancing act between two jobs: hold enough water for the plant to drink, and hold enough air for the roots to breathe. It does both by having structure — chunky bits that create pockets. Water clings to the particles and drains out of the gaps, and the gaps are where the oxygen lives. That structure is the whole point.

What an airy mix is usually made of

A base like peat-free compost or coco coir that holds moisture and nutrients
Perlite — the white puffed volcanic bits that hold open air pockets and speed drainage
Bark or coarse grit for chunkier structure, especially for aroids and succulents
The result: it drains fast, then holds a little moisture and a lot of air

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