Can I use garden soil in pots and containers?

You can, but it usually goes badly, and the reason is physics rather than fertility. Soil that behaves well in the ground behaves very differently once it is confined in a container.

In open ground, water drains away through a deep column of soil and air is drawn in behind it. A pot is a shallow, closed box with a few holes in the bottom. Water cannot drain past the base, so a saturated layer forms at the bottom regardless of soil type — and the finer the particles, the thicker that layer is. Garden soil, particularly anything with clay in it, holds water tightly and slumps into a dense mass after a few waterings. The result is compost that is waterlogged at the bottom, hard and cracked at the top, and short of the air roots need.

Potting composts are formulated to avoid this. They use coarse, structured materials — composted bark, coir, wood fibre, grit, perlite — that hold water in the spaces between particles while keeping large air-filled pores open, and they resist compaction over a season.

Garden soil also brings weed seeds, fungal pathogens, slug eggs and vine weevil larvae straight into a confined space where they have no natural predators.

The practical compromise is to use garden soil as one component rather than the whole thing. For large permanent containers and raised beds, where buying enough compost is genuinely expensive, a mix of roughly one-third good topsoil, one-third compost and one-third grit or bark drains acceptably and stays structured. For seeds, cuttings, small pots and houseplants, use a proper potting compost — the margin for error is too small otherwise.