Soil pH is a critical factor for gardening success. Some plants thrive in neutral soil while other plants prefer soil that is on the acidic side. The difference lies in the plant’s ability to use nutrients present in the soil. For plants that prefer an acidic soil a critical nutrient is iron. Iron is most available in soil with a pH of around 5.5. Without iron, acid-loving plants will turn yellow and suffer stunted growth.
Testing and Adjusting Soil pH
Before planting any plant it is best to know the optimum pH range that the plant will thrive in and the pH of the soil in which you will be planting. “The right plant in the right place” is always the best policy. Purchase a pH test kit or meter. This will give you a more in-depth soil analysis along with the pH. To correct soil pH it is imperative that you know the soil pH before you attempt to change it. Adding shredded pine needles, composted oak leaves, or peat moss will all assist in lowering soil pH over time. A quicker fix is the addition of two materials commonly used for this purpose: aluminum sulfate or garden sulfur. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil. Garden sulfur requires some time for the conversion to sulfuric acid with the aid of soil bacteria. The conversion rate is based on the fineness of the sulfur, the amount of soil moisture, soil temperature, and the presence of bacteria. Based on these factors, the conversion rate of sulfur may be very slow. It may take several months, if the conditions are not ideal, to react. Acidifiers should be worked into the soil after application in order to be effective. Do not apply to the surface of plant leaves or burning may result. Read and abide by manufacturer instructions when applying acidifiers. Keep in mind that it takes time to alter soil pH and your soil will tend to revert to its old pH over time, necessitating repeat treatment. Attempting to change soil pH too quickly may shock and kill a plant. A good rule of thumb is to adjust to no more than one point per season. Fertilizers recommended for acid loving plants do not assist in adjusting the soil pH.
Acid Loving Trees & Shrubs
Azalea
Bayberry
Blueberry
Camelia
Dogwood
Fothergilla
Gardenia
Heath
Heather
Holly
Hydrangea
Itea
Leucothoe
Magnolia
Mountain Laurel
Oak
Pieris
Pine
Raspberry
Rhododendron
Spruce
