pH is a measure of the acidity or alkalinity of a solution on a scale from 0 to 14, where 7 is neutral. In hydroponics and soil growing, pH directly controls which nutrients are chemically available to plant roots. Most crops grow best at a pH of 5.5β6.5 in hydroponic systems.
Key Facts
- Scale runs 0β14: below 7 is acidic, above 7 is alkaline, 7 is neutral
- Hydroponic target range: 5.5β6.5 (slightly acidic) for most crops
- Soil target range: 6.0β7.0 depending on crop
- Out-of-range pH causes nutrient lockout β plants cannot absorb minerals even if present
- pH drifts over time as plants absorb nutrients and water evaporates
- Adjust with pH Up (potassium hydroxide) or pH Down (phosphoric acid)