If you’re an indoor gardener or hydroponics enthusiast, understanding the role of PPM (parts per million) and EC (electrical conductivity) in your nutrient solution is critical for success.
These two key measurements provide insight into how concentrated your nutrient solution is, helping you avoid nutrient deficiencies or toxicities. By following the correct PPM and EC benchmarks for each grow phase, you can ensure your plants thrive, whether you’re growing leafy greens, herbs, or flowering crops like cannabis.
In this guide, we’ll break down each growth phase and provide actionable benchmarks to guide your feeding strategy, optimize nutrient uptake, and maximize yields.
What Are PPM and EC?
PPM (Parts Per Million): Measures the concentration of nutrients in your water solution. It tells you how many milligrams of nutrients exist per liter of water.
EC (Electrical Conductivity): Measures how well your nutrient solution conducts electricity, which correlates with the concentration of dissolved salts (nutrients).
Quick Tip: PPM and EC are directly related. Use a reliable conversion factor (typically 0.5 or 0.7) to switch between them.
Why Monitoring PPM and EC Matters
Monitoring PPM and EC ensures your plants receive the right nutrient levels:
-
Prevents nutrient deficiencies
-
Avoids nutrient burn
-
Optimizes plant growth and yield
-
Helps troubleshoot growth problems early
PPM & EC Benchmarks for Each Grow Phase
Seedling Phase
PPM: 100–250 ppm EC: 0.2–0.4
Seedlings are sensitive to high nutrient concentrations. Overfeeding can damage delicate roots.
Tips:
-
Start with 1/4 strength of your base nutrient solution.
-
Keep pH levels around 5.8–6.2.
-
Use soft water to avoid excessive salts.
Vegetative Phase
PPM: 300–600 ppm EC: 0.6–1.2
During vegetative growth, plants require more nutrients to develop strong stems and foliage.
Tips:
-
Gradually increase nutrient strength over 1–2 weeks.
-
Focus on higher nitrogen levels to promote leafy growth.
-
Maintain consistent watering and monitor for nutrient lockout.
Pre-Flowering Phase
PPM: 500–800 ppm EC: 1.2–1.6
As plants transition to flowering, their nutrient needs shift.
Tips:
-
Reduce nitrogen slightly and increase phosphorus and potassium.
-
Monitor plant response and adjust feeding frequency.
-
Maintain pH at 5.8–6.0 for hydro systems.
Flowering Phase
PPM: 700–1,200 ppm EC: 1.5–2.2
Flowering plants need higher nutrient concentrations for robust bud formation.
Tips:
-
Focus on phosphorus and potassium for flowers.
-
Avoid over-fertilization; slow increases are safer.
-
Watch for leaf tip burn and adjust EC if necessary.
Late Flowering/Harvest Phase
PPM: 400–800 ppm EC: 0.8–1.5
Towards the end, plants may need lower nutrient levels to finish flowering naturally.
Tips:
-
Gradually decrease nutrient concentration.
-
Consider a flushing period 1–2 weeks before harvest.
-
Monitor leaf color and adjust as needed.
Adjusting PPM and EC for Plant Type
Different plants have varying nutrient requirements:
-
Leafy greens & herbs: Generally prefer lower EC (0.8–1.2) and consistent moisture.
-
Fruiting crops (tomatoes, peppers): Require moderate EC (1.2–1.8) for optimal fruiting.
-
Cannabis: EC varies from 0.6 in seedlings to 2.2 in full bloom.
Tools and Tips for Accurate Measurement
-
EC meter: High-precision meters ensure accurate readings.
-
PPM meter: Useful if you prefer working with PPM.
-
Regular calibration: Always calibrate your meters for reliable results.
-
Record keeping: Maintain a daily log to track nutrient adjustments.
Common Mistakes to Avoid
-
Feeding too early or too much
-
Ignoring water quality
-
Not monitoring pH alongside EC/PPM
-
Skipping regular meter calibration
-
Failing to adjust for seasonal or environmental changes
Monitoring PPM and EC is a cornerstone of successful hydroponic and indoor gardening.
By following these benchmarks for each grow phase, you can optimize plant health, avoid nutrient-related issues, and maximize yields. Remember to invest in quality nutrients, keep accurate logs, and adjust your solution according to plant type and growth stage.
For more tips and high-quality nutrient products, explore Humboldt's Secret Supplies and take your garden to the next level.
Keep growing smarter. Visit our blog for weekly tips, video tutorials (HSSTV), and expert-driven insights.