In a nutshell “pH” (potential for hydrogen) stands for the concentration and activity of the element hydrogen in the various moist components of your garden soil. For example the H in H2O means two hydrogen atoms attached to one oxygen atom, they form water. Water combines with soil carbon to form sugars, and plants have a sweet tooth!
“Sour” soils with little accessible hydrogen have a low pH number; they are acidic—like vinegar. “Sweet” soils with lots of available hydrogen have a high pH number; they are salty—like seawater.
Plants concoct custom made sugars to feed themselves so ingredients in the soil are important to their health. Hydrogen is volatile stuff; it easily combines with other chemicals to feed or starve plants.
PEAT MOSS you buy in rectangular blocks at garden suppliers is, as far as azaleas and blueberries are concerned, vinaigrette dressing-—high acid, little available hydrogen, but you will like the taste of your cabbages better if they’ve had a serving of low acid, salty lawn lime or fireplace ashes instead.
Between these extremes most garden vegetables prefer neutral soil with middle-of-the-road pH.
The rule of thumb in The Eat Crow Club is that soils in moist climates—regardless of their sand or clay structure—tend to be vinegar, and soils in dry climates tend to be seawater.
DIFFERENT parts of the average suburban garden can have different pH measurements, just like they can have different structures. You may have your soil tested for its average pH then begin the multi-year chore of buying and adding chemicals, OR you can amend the soil toward pH neutrality by adding all the compostable materials you can corral, which also improves its structure and water-holding capacity. Most gardeners I know tend to do a combination of the two practices.
Over time, plants consume whatever you give them to eat, so the soil is always thinning and reverting to its original condition, and what they didn’t tell you in high school chemistry class—or maybe you were not listening—is that pH is ever with us.
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