Short answer
In soil, water when the top 1 to 2 inches (2.5 to 5 cm) of the medium feels dry. A plant in a 3 to 5 gallon pot under strong light takes a drink every 2 to 3 days in veg and every 2 to 4 days in flower. In coco coir, roots fill the pot and you water daily. In deep water culture or any recirculating hydro setup, roots sit in water at all times, so an interval does not apply. You maintain the reservoir instead.
how often to water cannabis plants
There is no fixed calendar. The plant, the pot, the medium, and the room set the pace. Your job is to read the medium and match it.
What controls the interval
- Pot size versus plant size: a small plant in a large pot dries out slow, so stretch the gap.
- Medium: peat and compost hold water, coco and perlite-heavy mixes drain fast.
- Stage: seedlings sip, a flowering plant in week 6 can drink a gallon a day.
- Environment: 85F with low humidity shortens the gap, 72F with high humidity lengthens it.
- Airflow: a fan across the canopy pulls moisture out of the pot.
Prerequisites
- Pots with drainage holes and a saucer or tray under each one.
- Water at 65 to 72F.
- pH target: 6.0 to 7.0 for soil, 5.5 to 6.5 for coco and hydro.
- A moisture meter or a finger, plus a way to weigh the pot.
Steps
- Push a finger or moisture probe 2 inches into the medium at the edge of the pot, not at the stem.
- Lift the pot and note the weight. A light pot with a dry top zone is ready.
- Mix nutrients and set the pH to the target for your medium.
- Pour at the base of the stem and work outward to the rim.
- Stop when 10 to 20 percent of the water you poured runs out the bottom.
- Wait 15 minutes, then empty the saucer so the pot does not sit in runoff.
- Write down the date and how long the medium took to dry.
- Set the next watering for the day the pot hits that same weight and dryness.
Signs you are off
- Overwatered: drooping leaves with firm, heavy pots, algae on the surface, fungus gnats.
- Underwatered: crispy edges, pots that feel hollow, medium pulling away from the pot wall.
- Both problems look alike at the leaf. The pot weight tells you which one you have.
Interval by medium
- Soil: every 2 to 3 days in veg, 2 to 4 in flower.
- Coco coir: daily to every other day in veg, once or twice daily in late flower.
- Peat-based mixes: every 3 to 4 days.
- Hydro with a reservoir: check daily, top off every 2 to 3 days.
Where convenience fits
Drip lines, capillary mats, and self-watering bases turn a 3 day rhythm into a 1 week reservoir fill. That saves trips, and it also hides mistakes. A timer that fires while the medium is still wet drowns the root zone in 4 days. Run any automated setup by hand for a full week first, log the dry-back time, then hand it the schedule your plant already proved.