How to Read a Cannabis Leaf Like a Diagnostician
You do not need to memorize thirty deficiency charts. You need one concept — nutrient mobility — and then most symptoms sort themselves.
The core concept
Mobile nutrients like nitrogen, phosphorus, potassium, and magnesium can be moved by the plant from old leaves to new growth. So deficiencies of these appear on lower, older leaves first.
Immobile nutrients like calcium, iron, sulfur, boron, and zinc cannot be relocated. Their deficiencies appear on new top growth first.
Then look at pattern
Uniform yellowing points toward nitrogen. Yellowing between green veins points toward magnesium or iron depending on location. Spots point toward calcium or a pathogen. Tips and margins burning points toward excess, not deficiency.
Always check pH before dosing
Most apparent deficiencies in home grows are pH lockouts. Confirm pH first and you will avoid making the root zone worse.
Photograph under white light
Purple LED light hides color entirely. Take the leaf out of the tent or use a white flashlight before diagnosing anything.
Frequently asked questions
- What if I see several symptoms at once?
- Multiple simultaneous symptoms almost always mean pH lockout or salt buildup rather than several real deficiencies.