Due to the chemistry of the situation, nutrients in the soil are more or less available to a plant depending on the pH (acidity or alkalinity) of the soil. Generally, most landscape plants do best in a slightly acid soil with a pH of about 6.0 to 7.0. Certain plants such as rhododendrons and azaleas, boxwood, pin oak and others are "acid loving" and need a pH of around 5.0 to thrive.

The reason soil pH is important is its impact on the availability of nutrients. If the pH is in the proper range for the plant, nutrients will enter into soil solution with water and move into the roots of the plant. If the pH is outside the desired range, this process will either not happen or happen at a lower level leading to nutrient deficiencies in the plant even though there are adequate levels of the nutrient in the soil.

Notice in the chart below that most of the major plant nutrients are most available at a pH of between 6.0 and 7.0. Is it a coincidence that this is also the level where most landscape plants thrive? I wonder.