A measure of how acidic or alkaline soil is, on a scale from 0 to 14. A pH of 7 is neutral; below 7 is acidic; above 7 is alkaline. Soil pH controls which nutrients are available to plant roots. Most garden plants grow best in slightly acidic to neutral soil (pH 6.0–7.0). Soil pH is tested with an inexpensive home kit or through a cooperative extension service.