When is the soil too wet to dig or walk on?

There is one avoidable mistake that does more lasting damage to a garden soil than anything else, and it is walking on it or digging it when it is saturated. Wet soil has no strength: the particles slide past each other, the air spaces close, and on clay the result sets into something close to unfired pottery which then takes years of frost and worms to undo.

Step by step

1. Take the pinch from where you plan to work.Not from the path, not from a dry corner. Soil moisture varies across a garden by a lot, and shaded beds under a north wall are still saturated weeks after an open bed has dried.
2. Rub it between finger and thumb and look at what happens.A smooth, shiny, continuous smear with no visible individual particles means too wet. A break into distinct crumbs, with the particles still visible, means ready. Dust that will not cohere at all means too dry to plant into.
3. Test at spade depth as well as at the surface.In February and March a windy few days dries the top 30mm convincingly while 150mm down is still waterlogged. Dig a small hole and test the soil from the bottom of it before committing to a day's digging.
4. Use the boot test as a second opinion.If soil sticks to your boots in lumps and you leave a footprint that holds water, the answer is no. If it brushes off dry-ish and the print crumbles at the edges, you are fine.
5. Stay off entirely rather than treading carefully.There is no careful way to walk on saturated clay. Body weight over the area of a boot sole is enough pressure to close the pore structure regardless of how gently you place your feet.
6. Lay a board if you genuinely must cross.A scaffold board spreads your weight over ten times the area. It is not free of damage but it is a fraction of it, and it is the standard answer for winter harvesting from a bed you cannot reach across.
7. Judge planting separately from digging.Soil can be fine to walk on and too dry to plant into. A rootball put into a dry hole sits in a dry pocket and the surrounding soil wicks water away from it. Water the ground thoroughly the day before, then plant.
8. Plan the garden so the question stops arising.Beds no wider than about 1.2m with permanent paths between them means you never need to stand on soil at all, in any weather. This is the single change that makes the whole problem go away.

Tips

• Sandy soils tolerate being worked far wetter than clay and recover much faster from being trodden. Chalk is somewhere in between. The rule matters most where the clay content is highest.
• Frozen soil is a special case: walking on frozen ground is fine, walking on it as it thaws is among the worst things you can do, because the top is saturated and the base is still rigid.
• Grass is more forgiving than bare soil but not immune — winter traffic on a lawn is exactly how the mossy compacted strip along a desire line forms.
• If you have to dig in wet conditions for an emergency — a burst pipe, a fallen tree — expect to have to repair the structure afterwards with a fork and organic matter, and plan for that rather than pretending it did not happen.

Common mistakes

• Digging over a clay vegetable plot in a mild wet January because the weather is fine for once — The classic. The soil looks workable because it is not raining that day. Clay dug wet dries into intractable clods that no amount of raking will reduce to a seedbed in spring.
• Judging by the surface only — A drying wind fools everyone. The top is crumbly and the layer you will actually be moving is saturated.