Compost versus premium potting mix: what is the difference?

These two products look similar and are often confused, but they serve very different purposes. Understanding the difference will save you money and help your plants thrive.

Premium potting mix is a specially blended growing medium designed for use in containers and raised beds. It is lightweight, free-draining, and usually contains starter nutrients. It is what you fill a Corrogarden raised bed with, not garden soil, which is too heavy, drains poorly, and can carry weeds and disease.

Compost is decomposed organic matter, made from plant material, food scraps, leaves and similar. It is dark, crumbly and rich in nutrients. Compost is a soil improver, not a standalone growing medium. Planting directly into compost alone is not recommended because it is usually too dense and nutrient-rich for seedlings.

How do compost and potting mix work together?

1. Start with a good quality premium potting mix as the base for your raised bed.
2. Add compost as a regular top-up, two to three centimetres across the surface every few months, to feed the mix and improve its structure over time.
3. Do not use garden soil in a raised bed. It compacts badly in a contained space and brings problems with it.

Can you plant directly into compost? Not as a standalone mix. Compost alone can burn seedling roots and drains poorly. Mix it into your premium potting mix instead, at roughly 10 to 20 per cent compost to the rest potting mix, for a great growing medium.

For more on filling your raised bed correctly, see our filling guide.

More garden guides: how to fill your bed · how to fertilise a raised bed · how deep should your bed be?

What should I plant right now? Our free garden calendar shows what suits your postcode this month. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: Daderot, CC0, via Wikimedia Commons.