Essential elements
What nutrients do cannabis plants need?
Cannabis uses 17 essential elements, including nitrogen, phosphorus and potassium. Account for what the water, medium and fertilizer already supply; more fertilizer is not automatically better.
Primarily from air & water
C CarbonH HydrogenO Oxygen
These elements form much of the plant’s structure. Fertilizer is only one part of its needs.
Primary macronutrients
N NitrogenP PhosphorusK Potassium
Needed in relatively large amounts and central to fertilizer grades.
Secondary macronutrients
Ca CalciumMg MagnesiumS Sulfur
Also essential. Account for what the water, medium and fertilizer already supply.
Micronutrients
Iron · Manganese · Zinc · Copper · Boron · Molybdenum · Chlorine · Nickel
Required in much smaller amounts. Adding more can still cause an imbalance.
- N Nitrogen
- Supports proteins, chlorophyll and leaf growth.
- P Phosphorus
- Supports energy transfer and development.
- K Potassium
- Helps regulate water balance and enzyme processes.
A fertilizer’s N-P-K grade reports total nitrogen, available phosphate as P₂O₅ and soluble potash as K₂O, by weight. It is not a mixing rate. Use the NPK label reader to compare grades, or read the growth-stage ratio guide for development-stage context.
Growing medium
How does the medium change the starting point?
Existing nutrients, water chemistry and root conditions shape the program. Compare organic amendments and soluble mineral fertilizers in the context of the medium.
Soil & amended mixes
Organic matter and mineral reserves can contribute nutrients. Aeration, moisture and microbial activity affect availability.
Establish first What does an appropriate soil or substrate test show is already present?
Coco & soilless substrates
These systems often depend more directly on supplied fertilizer. Water chemistry, drainage and nutrient balance still matter.
Establish first What substrate, irrigation method and fertilizer program are being used?
Water culture
Roots depend on a balanced solution, dissolved oxygen, suitable pH and sanitary equipment. Track measurements alongside reservoir changes.
Establish first What are the source-water analysis, solution readings and recent additions?
Manage a nutrient solution
Read what is supplied
Read the label before adding another product.
Check the current guaranteed analysis, mixing directions and system compatibility. A base feed may already supply the needed elements; supplements need a clear purpose.
For environmental and root-care context, explore the growing guides.
Choosing a hydroponic nutrient program: Start with a complete water-soluble base feed labeled for your growing method, then check its guaranteed analysis and mixing instructions against what your source water already supplies. Measure the water before mixing; track pH, EC, root conditions and plant response after feeding. A higher EC reading cannot tell you which nutrient is missing, and no single feeding ratio fits every system. For the next step, see nutrient-solution preparation and how to interpret EC.
Understanding readings
What do pH and EC tell you?
Use the two readings together, with the sample location, method and growing system recorded. Neither reading identifies a complete nutrient balance.
Acidity and availability
pH describes acidity and influences nutrient availability. A suitable pH does not establish that every nutrient is present in the right amount.
Understand pH measurementsDissolved ions, collectively
EC reflects how dissolved ions carry electricity. It does not identify individual nutrient concentrations. Record units and any PPM conversion scale.
Interpret EC and PPM scalesBefore adjusting
What should you check before changing the feed?
Yellow leaves, burnt margins and slow growth have several possible causes. An image alone rarely confirms a nutrient deficiency.
- Inspect the conditions.Review watering, drainage, roots, pests, light, temperature and recent changes.
- Check the measurement.Use a calibrated instrument and a sampling method suited to the medium. Record pH, EC units and any PPM scale.
- Review the inputs.Check water chemistry, fertilizer analysis, mixing directions and recent additions.
- Confirm the suspected cause.Use appropriate soil, substrate, solution or tissue testing where possible before making large corrections.
Keep a usable record.
Record the date, plant or zone ID, medium, sample location, readings with units, recent changes and next check. Keep observations separate from suspected causes.
Extra phosphorus, bloom boosters or aggressive flushing can worsen an imbalance. Review the flushing guide in the context of measurements and the selected medium.
Quick answers
Questions and optional examples
Are organic nutrients always better?
No single label makes a fertilizer universally superior. Nutrient availability, growing method, consistency, environmental footprint and measured crop results are more useful comparisons.
Should the feeding formula change during flowering?
Nutrient demand can change with development, but plant condition and the actual formulation matter more than a simplistic rule to eliminate nitrogen or maximize phosphorus.
What does EC tell you?
Electrical conductivity reflects how well dissolved salts carry electricity. It can reveal broad changes in solution strength but cannot identify which individual elements are high or low.
Do additives guarantee larger buds?
No. Yield and flower quality depend on genetics, light, environment, root health and adequate balanced nutrition. Marketing claims are not a substitute for comparative evidence.
Try three examples: labels, EC and leaf symptoms
The fertilizer says 4-2-3.
Does that tell you how many millilitres to add to a litre of water?
Reveal the label explanation
No. The grade gives percentages by weight: 4% total N, 2% available phosphate as P₂O₅ and 3% soluble potash as K₂O. It does not supply a volume-based mixing rate. Read the product’s directions for its intended use.
The reservoir’s EC has risen.
Does one higher reading prove that a particular nutrient is excessive?
Reveal the EC explanation
No. EC responds to dissolved ions collectively. Water loss or recent additions can change a reading, and EC does not identify individual nutrient concentrations. Check volume, units, calibration and the record before drawing a conclusion.
A leaf is turning yellow.
Is adding nitrogen enough to establish and correct the cause?
Reveal the symptom explanation
No. Moisture, root damage, pH-related availability, pests and other stresses can produce overlapping symptoms. Inspect the system and use appropriate testing to investigate the cause before choosing a correction.