Lettuce pH range
Maintain a reservoir pH of 5.6–7 when growing Lettuce (Lactuca sativa, a leafy greens crop) hydroponically. Below: why this range, how to measure, and how to correct drift without shocking the plants.
Target pH
Maintain reservoir pH at 5.6–7. pH controls how readily the roots can absorb each nutrient; outside this window the plant shows symptoms of deficiency even when the nutrients are physically present in solution.
Measure with a calibrated pH meter at the same time each day and log the reading. Drift of more than 0.3 units over 24 hours usually signals a reservoir change or a nutrient imbalance.
Correcting drift
If the reservoir drifts above or below target, adjust gradually. Large one-shot corrections shock roots and stress the crop — add half the indicated dose of pH Up or pH Down, wait 15 minutes, then retest. Our pH adjustment calculator estimates the dose for your reservoir size.
Sources
All numeric parameters on this page are drawn from the following extension and research sources.
- Cornell CEA Hydroponic Lettuce Handbook (Brechner & Both, 2013) (accessed 2026-04-20)
- UF IFAS Extension HS1422 — Growing Lettuce in Small Hydroponic Systems (accessed 2026-04-20)