How to measure soil pH in your garden

Why soil pH matters more than you think

You can buy the finest plants and spread top-quality fertiliser, but if your soil pH is wrong, nothing thrives. Soil that's too acidic or too alkaline locks up nutrients. Your plants starve while the food sits right in front of their roots.

GardenWorld helps you visualise a garden design suited to your soil type. Knowing your pH on top of that means you pick plants that genuinely match your ground.

What exactly is pH?

The pH scale runs from 0 to 14. Below 7 is acidic, above 7 is alkaline. Most garden plants do best between 6.0 and 7.0. Ericaceous plants like rhododendrons and blueberries prefer it more acidic (4.5-5.5). Lavender and clematis thrive in slightly alkaline soil.

How to test pH at home

Three methods work well for home gardeners.

Method 1: pH test strips

Buy a pack of pH test strips from your local garden centre. Mix a scoop of soil with distilled water, stir well and dip the strip in. After a minute, compare the colour with the chart provided. Simple, cheap and reasonably accurate.

Method 2: electronic pH meter

A step up in precision. Push the probe directly into moist soil and read the number. Costs around fifteen pounds from garden centres or online. Calibrate it regularly or the readings drift.

Method 3: soil analysis kit

The most complete option. Some RHS-approved suppliers offer kits that test nitrogen, phosphorus and potassium alongside pH. Takes longer but gives you the full picture.

What if the pH is too low?

A pH below 5.5 is too acidic for most garden plants. The fix: apply garden lime. It raises the pH gradually. Spread it in autumn so it has time to work in. How much you need depends on your soil type. Clay needs more lime than sand to achieve the same shift.

Avoid quicklime or slaked lime unless you know exactly what you're doing. They're aggressive and can harm soil organisms. Ordinary garden lime (calcium carbonate) is safe and widely available.

What if the pH is too high?

A pH above 7.5 makes iron, manganese and other trace elements hard to absorb. You'll spot it as yellowing leaves with green veins. The fix: acidify with sulphur chips or add pine needle compost and peat-free ericaceous compost. This works more slowly than liming, so patience is needed.

Test in multiple spots

Soil pH can vary significantly across your garden. Test at least three locations: the lawn, a border and the veg patch. Keep a record so you can compare year on year. A simple notebook saves you a lot of guesswork later.

When to test

Test preferably in spring or early autumn. Not straight after heavy rain and not right after fertilising. The soil should be moist but not saturated for a reliable reading.

Know your soil, know your garden

Testing pH takes ten minutes and costs a few pounds, but it can mean the difference between a garden that struggles and one that flourishes. Test regularly, correct where needed and choose plants that suit your acidity level. Head to GardenWorld to design a garden that fits your soil conditions exactly.