Quick answer
Cannabis in veg grown in soil needs water every 2 to 4 days. Plants in coco coir need water once or twice per day by late veg. The pot sets the schedule, not the calendar. Water when the top 1 to 2 inches (2.5 to 5 cm) of media feel dry, or when the pot feels light.
cannabis watering schedule by stage
What sets the interval
- Pot size. A 1-gallon pot dries in 1 to 2 days. A 5-gallon pot holds water for 3 to 5 days.
- Media. Coco holds less water than peat or compost mixes, so it needs more events.
- Plant size. A plant at 30 inches with a full canopy drinks 2 to 3 times as much as a plant at 10 inches.
- Room conditions. A room at 85 F and 40% relative humidity dries a pot faster than a room at 75 F and 60%.
- Airflow. A fan pointed at the pot surface raises evaporation.
- Roots. Roots fill the pot between week 4 and week 6 of veg. Water use climbs as the root ball expands.
How to check a pot
Lift the pot after watering. Lift it again 2 days later. The change in weight shows how much water is left. A moisture meter read at 4 inches (10 cm) depth gives a second number. A finger pushed 2 inches into the media works too. Do not water on a fixed day count. Check first, then water.
Cannabis Seedling Watering Schedule: First 2 Weeks
Water volume per event
Common practice is to pour until 10% to 20% of the volume applied drains from the bottom. A 5-gallon pot takes about 2 to 4 quarts (1.9 to 3.8 L) to reach that point. Skip the runoff and salts from fertilizer collect in the root zone. Small pots need less. A 1-gallon pot takes about 1 pint to 1 quart.
Media types
- Soil mixes: every 2 to 4 days. Let the top 1 to 2 inches dry before the next event.
- Coco coir: once per day in mid veg, twice per day in late veg. Coco holds air at field capacity.
- Peat-based soilless mixes: every 1 to 2 days.
- Deep water culture and other hydro: continuous flow. Reservoir level and dissolved oxygen set the schedule.
Signs you are off schedule
Too little water: leaves droop, petioles bend, the pot feels light, and the media pulls away from the pot wall. Too much water: media stays wet for 4 or more days, leaves curl down, growth stalls, and fungus gnats or algae show up on the surface. Overwatering is the most common cause of stalled veg plants. Roots need oxygen. Saturated media blocks gas exchange. Fix: stop watering, raise airflow, and wait for the pot to lose weight.
Water temperature and pH
Target 62 F to 72 F (17 C to 22 C) for the water. Water above 75 F holds less dissolved oxygen. Common pH targets are 6.0 to 7.0 in soil and 5.8 to 6.2 in coco. Test the input water and the runoff.