Plant Nutrients 101
Understanding NPK ratios, macro and micronutrients, and how to feed your plants for optimal growth — in soil, hydroponics, or any system.
What is NPK?
NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K) - the three primary nutrients plants need in the largest quantities. You'll see NPK ratios on every fertilizer label, like “10-5-5” or “3-1-2”.
N
Nitrogen
Drives vegetative growth. More N = more leaves.
P
Phosphorus
Essential for roots and flowers. More P = better blooms.
K
Potassium
Overall health and fruit quality. More K = stronger plants.
Macronutrients Explained
Let's dive deeper into each primary nutrient - what it does, and what happens when you have too little or too much.
Role:
Leaf and stem growth, chlorophyll production, protein synthesis
Deficiency Signs:
Yellow lower leaves, stunted growth, pale green color
Excess Signs:
Dark green leaves, weak stems, delayed flowering
Role:
Root development, flowering, fruiting, energy transfer
Deficiency Signs:
Purple/red leaves, poor root growth, delayed maturity
Excess Signs:
Zinc and iron deficiency symptoms, stunted growth
Role:
Water regulation, disease resistance, fruit quality
Deficiency Signs:
Brown leaf edges, weak stems, poor fruit development
Excess Signs:
Calcium and magnesium deficiency, salt buildup
Secondary Nutrients
These nutrients are needed in moderate amounts. Most hydroponic nutrients include them, but they're often supplemented separately.
Ca
Calcium
Cell wall structure, root growth
Mg
Magnesium
Chlorophyll center, enzyme activation
S
Sulfur
Protein synthesis, enzyme function
Micronutrients (Trace Elements)
Needed in tiny amounts but absolutely essential. Deficiencies are rare with quality nutrients but can cause serious problems.
Iron
Chlorophyll synthesis
Manganese
Photosynthesis, enzyme activation
Boron
Cell division, sugar transport
Zinc
Hormone production, leaf development
Copper
Enzyme function, reproduction
Molybdenum
Nitrogen metabolism
Feeding by Growth Stage
Plants need different nutrient ratios at different growth stages. Here's a general guide:
Seedling
Light feeding, focus on root development
NPK
1-1-1
EC
0.5-1.0
Vegetative
High nitrogen for leaf growth
NPK
3-1-2
EC
1.2-2.0
Flowering
More phosphorus for blooms
NPK
1-3-2
EC
1.5-2.2
Fruiting
Potassium for fruit quality
NPK
1-2-3
EC
1.8-2.5
Mixing Your Nutrient Solution
Follow these steps for a perfect mix every time:
- 1
Start with clean water
Use filtered, RO, or dechlorinated water
- 2
Check base water EC
Subtract from target EC to know how much to add
- 3
Add nutrients to water
Never water to concentrate! Add slowly while stirring
- 4
Mix Part A first, then Part B
Never mix concentrates directly together
- 5
Check and adjust EC
Add more nutrients or water as needed
- 6
Adjust pH last
Target 5.5-6.5 using pH Up/Down
- 7
Let it sit 15 minutes
Re-check pH and EC before using
Calculate Your Nutrients
Use Truleaf's nutrient calculator to get precise NPK recommendations for your plants.