N-P-K Explained: How to Read a Fertilizer Label

Quick answer: Fertilizer labels show three numbers like 10-10-10. These represent N (Nitrogen) for leafy growth, P (Phosphorus) for roots/flowers, and K (Potassium) for overall strength. A balanced fertilizer (like 10-10-10 or 20-20-20) works for most houseplants. Flowering or fruiting plants often benefit from higher phosphorus. Stop guessing—use the VerdeBotany AI Plant Doctor Tool for a personalized fertilizer match.

What Does N-P-K Stand For?

N = Nitrogen: Promotes lush, leafy green growth.
P = Phosphorus: Supports strong roots, buds, and blooms.
K = Potassium: Helps with overall vigor, disease resistance, and stress tolerance.

Takeaway: Each nutrient has a role—too much or too little causes visible issues in your plant’s leaves and growth.

How to Read the Numbers

A fertilizer labeled 10-10-10 means it contains:

10% Nitrogen
10% Phosphorus
10% Potassium

The rest is filler or other trace nutrients. A higher number doesn’t mean “better”—it just means a stronger concentration, usually diluted with water before use.

Which Ratios Work Best?

Balanced (10-10-10 or 20-20-20)

Best for: Most foliage plants (pothos, philodendron, monstera). Provides all-around support.

High-Nitrogen (e.g., 20-10-10)

Best for: Leafy plants where green growth is desired.

High-Phosphorus (e.g., 10-30-20)

Best for: Flowering/fruiting plants like orchids, African violets, anthurium.

High-Potassium (e.g., 10-10-20)

Best for: Plants under stress or needing stronger roots and disease resistance.

Signs of Nutrient Imbalance

Low Nitrogen: Pale leaves, slow growth.
Low Phosphorus: Weak roots, poor flowering.
Low Potassium: Leaf edges burn, poor stress resistance.

Note: These symptoms can overlap with watering or light issues. Use the AI tool for an accurate diagnosis before adding fertilizer.

Organic vs. Synthetic Fertilizers

Organic: Fish emulsion, compost teas, worm castings. Gentler and improve soil health, but act more slowly.

Synthetic: Concentrated and fast-acting. Easy to measure and predictable, but can cause salt buildup if overused.

Real-World Example

Case study (2025): A VerdeBotany user had a peace lily that refused to bloom. The AI tool flagged low phosphorus and recommended a 10-30-20 orchid fertilizer at half strength every 3 weeks. Within 2 months, blooms appeared.

Personalize Your Fertilizer Plan

The VerdeBotany AI Plant Doctor Tool calculates the right N-P-K ratio, dose, and schedule for your specific plant, pot size, and environment. No more confusing labels—just clear, personalized instructions.

Get Your AI Fertilizer Match →

Helpful Internal Links

N-P-K FAQ (2025)

Do all fertilizers list N-P-K?

Yes—by law in most countries, fertilizer labels show these three primary nutrients as percentages.

Can I use outdoor fertilizers indoors?

Yes, but dilute more (¼–½ strength). Indoor plants need gentler feeding since they grow slower.

What about micronutrients?

Some fertilizers also contain calcium, magnesium, or iron. These help, but focus on N-P-K first for healthy growth.

Is higher N-P-K always better?

No—stronger fertilizers risk burning roots. Matching the ratio to your plant’s needs matters more than the raw number.