pH is a measure of how acidic or alkaline a solution is. It ranges from 0 to 14, with 7 being neutral. pH affects plant growth by influencing the availability of nutrients and minerals in the soil. Different plants have different pH preferences, depending on their adaptation to their natural environment. For example, plants that grow in acidic soils (pH 5.0 to 5.5) include azaleas, rhododendrons, blueberries and conifers. Plants that grow in slightly acidic soils (pH 5.8 to 6.5) include vegetables, grasses and most ornamentals. Soil pH can be altered by adding lime or sulfur, depending on whether the soil is too acidic or too alkaline.