The lone voice of horticultural reason

“Adding peat moss to your soil will lower the pH”

True, but only to a very small degree.

A lot of times, gardeners cast peat moss onto their garden beds at various times of the year in the mistaken belief that they are lowering the pH. They add a layer around azaleas, or blueberries, for instance. A test of the soil in the root zone before and at any time after would show a negligible change in pH, or none at all.

Truth is, you can add two big bales of the stuff (eight cubic feet) and rototill it in to a bed as small as 100 square feet and with luck you’ll drop the pH by half a percent. Not much good if you’re dealing with sweet soil with a pH of, say, 7.5. You’ll only knock it down to 7.0 (neutral).

The best way to lower soil pH is to use soil sulfur, in the amount prescribed by a proper soil test. If you want to grow blueberries, for instance, you can send in your soil and note that your intent is to grow blueberries. A good university test will tell you exactly how much soil sulfur to add.

Peat moss is fairly wimpy as a general soil additive, it should be noted. Yes, it lightens the soil, and retains moisture, and is a good choice for mixing with black dirt and a little sharp sand if you are making your own potting soil. But realize that peat moss compacts very quickly. Two, three years after adding it to soil, it’s about gone. Compost and composted rice hulls are better overall soil additives.

Don Engebretson
The Renegade Gardener