2 Accurate Ways to Test Soil pH, According to a Pro

Anyone who has picked up an instructional gardening book has gleaned that it might be important to test your soil’s pH before embarking on any major planting project—but too often gardeners skip this vital step. “Newbie gardeners don’t test for pH mostly because they don’t know it matters,” says Daryl Beyers, author of The New Gardener’s Handbook and the Coordinator of the Gardening Certificate Program at the New York Botanical Garden.

But as the authors of the stalwart and indispensable Reader’s Digest Illustrated Guide to Gardening write, “To make the best use of the soil in your gardening you should know its properties.” If you’ve avoided testing your soil because it feels intimidating, read on to find out the best (and easiest!) ways to test your soil pH.

What is the best way to test soil pH?

The ideal way to test pH is to send it to a lab. Wait, wait, don’t stop reading at the word “lab!” A lab test is simpler than you think–and probably easier than one of the at-home soil testing kits.

Beyers explains, “Every state university has a soil lab that does this and it’s not too expensive.” You’ll dig up some sample soil, mail it in, and wait a week or two to get your results; fees usually range from free to $50.

Plus, the test also tells you a lot more about your soil, like fertility, texture, and nutrient content–all essential information you should know.

How can I test soil pH at home?

If you want to go the do-it-yourself route, Beyers recommends using a pH meter. “These devices are easier to use than the paper strips because you can check more areas faster without all the fuss of mixing the soil in water and dipping in the strip,” he says. “Plus, sometimes it’s hard to tell exactly what the color of the strip is to get the right pH reading.”

But Beyers cautions the quality of the meter matters, noting that a $12 meter from the hardware store will be okay, but there are pricier but highly accurate scientific meters. Consider getting a gardening buddy or two to go in on one as a group, or ask your local community group if anyone has one you can borrow. 

Beyers says to skip the pH testing hacks involving baking soda and vinegar that you may find online. “It’s just not very precise,” he says. One of these experiments will tell you if your pH is above, or below a neutral pH of 7, but not how much. Beyers explains that pH is a logarithmic scale which means a pH of 6.0 is 10 times more acidic than a pH of 7.0 and a pH of 5.0 is 100 times more acidic than a pH of 7.0, so the exact number is important. 

Why is it important to test your pH?

“The pH matters because it affects how the nutrients in your soil are absorbed by the plant,” says Beyers. “It’s like a little chemistry experiment going on underground with nutrients like nitrogen, potassium, phosphorus, magnesium and sulfur jumping from the soil to the plant roots. The pH, or acidity, of the soil affects how well those nutrients can be absorbed from the soil.”

This is important because plants need those minerals to make flowers, fruits, and roots, and some plants need more than others: Vegetables, for example, grow best in soil that is between 6 and 7 on the pH scale, while cabbage thrives in slightly alkaline soil (7.5) because the alkalinity deters clubroot fungus that often affects Brassicaceae.

Another classic example is hydrangeas, which like acidic soils. “It’s this acidity that makes the blue hydrangeas absorb the minerals they need to make their flowers blue,” says Beyers.

How can I fix my soil pH?

If you find out your soil pH is not ideal, don’t run out and spend a fortune on amendments. “It is always a better idea to select and grow plants that do well in the soil in your garden—and luckily most plants can tolerate a wide range of pH,” says Beyers. 

If your soil’s pH is extreme in some way, you can try to tweak the pH around the roots of existing plants to help them out; for example, you might add limestone to the soil around your boxwoods or lawn because they like alkaline soil, or you could amend with sulfur around the roots of your hydrangeas or azaleas, which prefer acidic soil (both limestone and sulfur are available at most garden centers). But in the future, pick plants to suit your soil. 

Still not convinced? Here’s one more reason to properly test your soil’s pH: Knowing this information will give you confidence. Executing this simple task gives you a feeling of accomplishment, and in the future when you’re wondering what is wrong with a plant, you can rule out pH because you know what you’re working with.