Reservoir or root zone cold (below 16 °C / 61 °F)
Lowest at the end of the dark period and in winter rooms with pots on concrete..
- Also called
- res too cold
- cold water in reservoir
- cold floor pots
- water temperature low
Likely causes, most likely first
Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.
PossibleCold root zone (below about 16 °C / 61 °F)
Fix: Raise root-zone temperature to 18-22 °C (64-72 °F): lift pots off cold floors onto insulation, warm the room at night, use an aquarium heater in reservoirs (with a thermostat), water with room-temperature solution.
Recovery: Growth resumes and new leaves green within a week.
How to confirm it
- Measure reservoir and root-zone temperature at the end of the light period. Measure the solution in the reservoir and in the root chamber or bucket, at the warmest time of day. Target 18-22 °C (64-72 °F). Above about 23-24 °C (73-75 °F), dissolved oxygen falls and Pythium risk rises; below 16 °C (61 °F) uptake slows.
- Lift the pot and check moisture at depth. Lift the pot right after a full watering to learn its wet weight, then lift before each watering. Water when it is clearly lighter (about half the added water gone). Push a finger or a moisture probe 5 cm (2 in) down. Heavy for 3-4+ days with droop: overwatering. Very light with limp papery leaves: thirst.
Look for
Thermometer in the reservoir or root zone at lights-on..
The full guide: Temperature by stage: day, night and root-zone targets
Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
