The pH of a plant or soil is a measure of the amount of acid or base in that environment. The pH scale runs from 0 to 14 and is used to describe the strength of the acid or base in a solution. A pH of 7 is neutral; anything below 7 is acidic, while anything above 7 is alkaline. A plant’s normal pH range is between 2.5 and 1.5. A pH below 2.5 is considered too low for most plants and is often called acidic. QA PH below 3 is an indication of root rot.