Q. How do I determine the pH of my garden soil and why is it important?

A. The pH of garden soil can be easily determined by using an inexpensive kit that can be purchased at hardware stores and large garden centers. Proper soil pH is particularly important to plants such as birch trees and hydrangea shrubs. Often, plants exhibit nutritional deficiencies that can be addressed by a pH adjustment. The symbol pH is used to express a level of acidity or alkalinity. A pH reading of 7.0 is considered neutral, readings below 7.0 are acidic, and readings above 7.0 are alkaline. Most garden plants grow satisfactorily in soils with a pH level of 6.0 to 6.5.

It is important to determine the pH of a soil prior to adding an amendment such as sulfur or lime. When using a test kit, deionized water should be used instead of tap water to prevent getting a pH reading of the water instead of the soil. Once your soil's pH is determined, sulfur or lime should be added according to package directions at rates that correspond with the pH test results. Adding sulfur will lower the pH of soil making it more acidic. Adding lime will raise the pH of soil, making it more alkaline. Soils in the Chicago area tend to be more alkaline, with a pH of approximately 6.0 and higher; therefore, adding lime to increase alkalinity is uncommon.