How can I tell if my garden soil is compacted?

The answer

Push a thin rod or screwdriver into moist ground and note where it meets firm resistance, then watch how water behaves after rain. Ponding on the surface, roots that grow sideways or stay stunted, and soil that breaks into hard plates or sharp-edged clods instead of rounded crumbs are common signs. Few earthworms and grey or mottled colours also hint at poor drainage. Digging a small hole to look at the structure gives the clearest picture.