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  • Writer's pictureMitchell Stern

What's Wrong With My Plant? - How to Diagnose Nutrient Deficiencies in Cannabis

Updated: May 23

If you've ever grown cannabis, you know just how easily nutrient deficiencies can occur. Fortunately, most cases of nutrient deficiencies and toxicities have simple solutions.


In this article, we're going to discuss

  • Leaf anatomy

  • Symptoms of essential nutrient deficiencies & toxicities

  • The importance of pH to nutrient availability

  • Treatment options for correcting nutrient imbalances



Table of Contents

Understanding Nutrients

Leaf Anatomy

Macronutrients

Micronutrients

The NPK Ratio

Why is pH Important?

The Plant Nutrient Deficiency Chart

Diagnosing a Nutrient Deficiency

Get to Know Your Nutrients



Understanding Nutrients

Nutrients are vital for plant growth and diagnosing nutrient can be difficult if you don't understand how nutrients interact with each other.


Before we learn how to diagnose nutrient deficiencies in cannabis plants, we'll need to learn a bit about how nutrients work on a cellular level.


Leaf Anatomy

Before we go any further, lets define a few terms:


Macronutrients

Macronutrients are elements that plants need in large quantities. These nutrients have a direct effect on critical plant functions, like amino acid (protein) formation, photosynthesis, and cellular respiration.


Nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur all fall into this category.


Micronutrients

Micronutrients play an indirect role in plant biology and must be present for certain chemical reactions to take place; such as protein synthesis and regulating osmotic pressure.


Micronutrient deficiencies often occur simultaneously.


Iron, boron, manganese, copper, molybdenum, chlorine, zinc, cobalt, vanadium, silicon, and sodium are all micronutrients.


Mobile vs. Immobile

In addition to being micro or macro, nutrients can also be categorized as Mobile or Immobile.


Mobility affects where nutrient deficiencies first appear so by understanding which nutrients fall into which categories, we are able to diagnose nutrient issues more accurately.



The NPK Ratio

The NPK ratio is prominently featured on the front of most nutrient products and soils. The NPK ratio represents the percentage (by volume) of Nitrogen, Phosphorus, and Potassium that the product contains.


The NPK ratio 18-24-12 is easy to see
The NPK ratio 18-24-12 is easy to see

Why is pH Important?

The plant's ability to absorb nutrients is heavily dependant on the pH of the soil in which the plant resides. Macronutrients tend to be more available at higher pH levels whereas micronutrients tend to be more available at lower pH levels.