Diagnosing injury to plants from herbicides can be difficult. This guide is intended to aid in assessing and identifying potential non-target herbicide injury. Knowing when and what was applied is vital for diagnosing herbicide injury. In addition, knowing weather conditions, soil type and soil pH, and other environmental factors that affect herbicide performance can be helpful. This guide first describes background information necessary to understand herbicide injury, then symptoms of herbicide injury are explained in the context of plant type and herbicide mode of action. Terms in bold are defined in the glossary.