Remember high school graduation when you swore you would never revisit chemistry topics like pH? Then you grew up and fell in love with showy azaleas. Your azaleas and bodacious Texas blueberries got “sick” in low-acid soil. The leaves turned yellow. Your cabbages grew just dandy in low alkali soil, but they tasted bitter. Welcome to The Eat Crow Club where backyard gardeners learn about “sweet” and “sour” soils, the topic of pH.
In a nutshell, “pH” (potential for hydrogen) stands for the concentration and activity of the element hydrogen in the various moist items in your garden soil. For example, the H in H2O means two hydrogen atoms attached to one oxygen atom, they form water. But wait, water can combine with carbon to form sugars; and, plants have a sweet tooth!
“Sour” soils, with little available 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 chemical ingredients in the cupboard are important to their health. Hydrogen is volatile stuff; it easily combines with other chemicals to feed or starve plants.
For another example, the peat moss you buy in those big rectangular blocks at garden supply places is, as far as azaleas and blueberries are concerned, vinaigrette dressing– high acid; but, you will like the taste of your cabbages better if they’ve had a serving of lawn lime or fireplace ashes, instead of peat moss.
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 yard and 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 leaves, twigs, pebbles and composts 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 gardens 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.