How do I find out what type of soil I have?

Almost every other decision in a garden follows from this one: how often you water, whether you can walk on the beds in February, what your feeding regime needs to look like, and which plants will thrive rather than merely survive. It takes two minutes to establish and most people never do it.

Safety

What you'll need

• A trowel
• A clean straight-sided jar with a lid (optional)
• A ruler (optional)
• Water

Step by step

1. Sample below the surface, not from the top.Scrape off the top 20mm of loose material and take from 100 to 150mm down. The surface is mulch, leaf litter and whatever you added last year — it tells you nothing about the soil underneath.
2. Sample from several places.Soil varies enormously across one garden, especially where a house was built. Take from four or five points, and keep them separate at first so you notice if one is different.
3. Do the ribbon test first.Moisten a walnut-sized lump until it is like putty — damp, not wet. Roll it into a ball, then squeeze it upward between thumb and forefinger to push out a flat ribbon over the edge of your finger.
4. Read the ribbon.No ball at all and gritty: sand. A ball that will not ribbon, feeling silky or soapy: silt. A ribbon over 50mm long, sticky, shiny where you rub it: clay. A short ribbon that crumbles, feeling crumbly rather than sticky: loam, which is what you want.
5. Run a jar test if you want proportions.Fill a straight-sided jar a third with soil, pick out stones and roots, top up with water leaving an air gap, add a drop of washing-up liquid, and shake hard for a full minute. Stand it somewhere it will not be knocked.
6. Read the jar after a day.Sand drops out within a minute, silt over a couple of hours, clay over a day or more. Measure each band and express it as a percentage of the total. Organic matter floats on top; ignore it in the sums.
7. Check the drainage as a separate question.Dig a hole a spade deep and wide, fill it with water, let it drain, then fill again and time it. Gone within a couple of hours is free-draining. Still standing the next morning is a drainage problem, and no amount of compost alone will fix it.
8. Look at the depth of good soil while the hole is open.The darker layer is your topsoil. Note where the colour changes to paler subsoil. Under 150mm is thin, and it explains a lot about a garden that struggles in dry summers.
9. Write the answer down.Soil type, drainage time, topsoil depth, and pH if you test it. You will refer to it for years and you will not remember it otherwise.

Tips

• Do the ribbon test when the soil is naturally moist, not baked or waterlogged. In a dry August you will get a false 'sand' reading from clay that has set hard.
• Most British garden soil is a mixture. The useful answer is which fraction dominates, not a laboratory classification.
• Look over the fence. Neighbours' gardens on the same geology have the same soil, and thriving rhododendrons next door tell you as much as a test kit.
• Chalky soil often gives an odd ribbon test — gritty with white flecks and free-draining. Look for pale stones and a shallow topsoil over solid chalk.

Common mistakes

• Testing a handful from the surface of a bed you improved last year — You will be testing compost, not soil. The point of the test is to find out what you are working with underneath everything you have added.
• Treating one sample as the answer for the whole garden — Builders' rubble, old paths, a filled-in pond and a former manure heap all sit under ordinary-looking lawns and change the result completely within a few metres.

Questions people ask