Can I tell whether my soil is acid or alkaline without a test kit?

You are never going to change the pH of an open garden by much, so what you actually need to know is which plants will be happy — and that question can be answered by looking rather than by testing. A kit gives you a number; the garden next door gives you the consequence of the number, which is more useful.

Step by step

1. Walk the street and look at established shrubs.Rhododendrons, azaleas, camellias, pieris, skimmia, magnolias and summer-flowering heathers growing large and dark green mean acid soil. If every garden has them, yours is acid too.
2. Look for the opposite indicators.Lilac, philadelphus, buddleja, ceanothus, bearded iris and clematis doing conspicuously well, plus box and yew hedging thriving, all lean alkaline. None of these is proof on its own, because they all tolerate a wide range.
3. Check a hydrangea.A mophead hydrangea that is genuinely blue is growing in acid soil, because blue colour needs available aluminium and that only happens below about pH 5.5. One that stays pink no matter what is planted in neutral or alkaline ground.
4. Look at the stones in the soil.White or cream chalk fragments, or grey limestone, mean alkaline. Old mortar and builders' rubble do exactly the same thing locally, which is why the soil beside a house wall is often several points higher than the soil at the end of the garden.
5. Read the weeds.Sheep's sorrel, plantain, horsetail and abundant moss lean acid. Field scabious, wild clematis, poppies and greater knapweed lean alkaline. Weeds are a weaker signal than shrubs — they respond to compaction and wet as much as to pH — so treat them as a hint.
6. Check the geology map.The British Geological Survey publishes free online mapping of surface geology by postcode. Chalk, limestone and boulder clay over chalk mean alkaline. Sandstone, peat and much of the acidic uplands mean the reverse. It takes two minutes and covers the whole garden at once.
7. Distrust the household tests.Vinegar fizzing on soil means free carbonate — genuinely alkaline. But no fizz proves nothing, because a mildly alkaline soil will not react. The bicarbonate-of-soda test for acidity is worse and rarely reacts at all. Neither gives you a number.
8. Buy the kit anyway if a decision depends on it.A chemical test kit costs less than a single shrub. If you are about to plant a hedge, a fruit garden or anything expensive, spend the money and test properly rather than reasoning from the neighbours.

Tips

• pH varies within a single garden, sometimes by a full point. A bed against the house, a former bonfire site and the far corner can all read differently.
• Acid-loving plants failing is much more visible than alkaline-loving plants failing. A rhododendron on chalk turns bright yellow between the veins within a season; a lilac on acid soil just sulks quietly.
• Long-term lawn and long-term woodland both acidify the soil beneath them slowly. Ground under conifers is often a point lower than the open garden beside it.

Common mistakes

• Concluding your soil is acid because moss grows in the lawn — Moss in a lawn is about shade, compaction and wet far more often than about pH. It is one of the least reliable indicators there is.
• Judging by a plant in a pot — A camellia thriving in a container tells you about the compost in the pot, not about the ground. Container evidence is worthless for this question.