Both come in similar bags, both are dark and crumbly, and both promise healthy plants. But using the wrong one is one of the most common reasons container plants fail and new beds disappoint.
The quick answer
| Garden soil | Potting soil (potting mix) | |
|---|---|---|
| Made from | Topsoil blended with compost or bark | Usually soil-free: peat or coir, bark, compost, perlite |
| Weight | Heavy | Light |
| Drainage in a pot | Poor: packs down and waterlogs | Good: stays airy |
| Best for | Improving beds and borders, filling large raised beds (mixed) | Pots, window boxes, hanging baskets, seed trays |
| Cost | Cheaper per volume | More expensive |
Why garden soil fails in pots
In the ground, soil sits on top of more soil, so water drains down and air moves through worm channels. In a pot there is no such continuity. Heavy soil settles, the bottom stays saturated and roots suffocate. Potting mix is designed to keep air spaces even when wet.
When to use garden soil
- Digging into existing beds and borders to add organic matter.
- Filling large raised beds, ideally mixed with compost (see our raised bed soil calculator).
- Levelling low spots in lawns and beds.
When to use potting mix
- All containers, from small pots to large patio planters and grow bags.
- Seed starting (use a fine seed compost or seed-starting mix).
- Houseplants, matched to the plant: gritty mixes for cacti, moisture-holding ones for ferns.
What about raised beds?
Raised beds sit between the two. They are in contact with the ground, so they drain better than pots, but filling a big bed with potting mix is expensive and it dries out quickly. A blend of topsoil and compost, sometimes with some aeration material, is the sweet spot.
How much potting mix do you need?
Containers swallow more than expected: a 40 cm (16 in) pot holds around 30 litres (1 cubic foot). Use our potting soil calculator for any mix of pot sizes, or the grow bag calculator for fabric bags.
Can you reuse potting soil?
Yes, for one or two seasons. Remove old roots, mix in a quarter fresh compost and a little slow-release fertiliser, and avoid reusing mix from diseased plants. After that, spread it on beds as a soil conditioner.
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