Upper vs. Lower Canopy – Determine if the abnormality is in the upper (newer growth) or lower (older growth) part of the plant. Problems in the upper canopy typically signify a micronutrient deficiency, while the lower canopy will show macronutrient issues, which can be fixed by applying potassium, nitrogen, phosphorus or magnesium.  

Discoloration – Most healthy plants should have evenly colored, deep green leaves. Reddish or purplish leaves usually indicate a phosphorus deficiency, while yellowing leaves often signal a shortage of nitrogen or potassium. The latter can be differentiated by how the yellowing progresses – if it is along the edge, it indicates a potassium shortage, but if it is down the middle of the leaf, the plant is likely deficient in nitrogen.

Plant height – Stunted growth is often a sign of a nutrient deficiency. Plants with extremely slow, stunted growth usually represent a potassium or phosphorus shortage, while spindly stalks signify a nitrogen deficiency. A plant with an abnormally small height is a simple way of diagnosing a nutrient deficiency, but this recognition should be used in combination with additional information (plant analysis/soil testing) to identify the particular deficiency and the best course of action.