How to Lower Soil pH Levels in Potted Plants

Check your soil with a pH kit available from home and garden centers. Follow the instructions that come with the kit. Typically, you add a soil sample and water, shake and let the wet material settle. Once it does, compare the color results of the liquid against a color chart printed on the kit’s container. This test will give you an idea of the current alkalinity or acidity of your soil.

Add a handful or so of peat moss or pine needles to the top of the soil. As this organic material decomposes, it adds acidity to the soil. The process is very slow, however, and you are not likely to see much change in the soil’s pH until several months have passed.

Sprinkle about 1/2 tsp. elemental sulfur across the top of the soil per 6-inch planting pot. When this element mixes with water and bacteria in the soil it forms sulfuric acid, which lowers the soil’s pH. However, if you are using sterilized potting soil, the bacteria is not present, so you can do one of two things: 1) mix the sulfur with some compost or soil from outside to introduce the bacteria, or 2) use a diluted solution of sulfuric acid. Add a few drops to the soil to bypass the need for bacteria to break down elemental sulfur.

Check the pH level of the soil weekly, if possible, to gauge how acidic the soil becomes.