Cannabis Watering Schedule for Seedlings: Day by Day

The Short Answer

Seedlings in their first two weeks need small, frequent waterings. Plan on 5 to 15 ml per plant every 1 to 2 days in a starter cup, rising to 20 to 50 ml by day 14. Water only when the top half inch of medium feels dry and the cup feels light. Most seedling deaths come from too much water, not too little.

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What Changes the Schedule

• Container size: a 2 oz cell dries out in a day. A 1 gallon pot holds moisture for several days.
• Medium: coco coir drains fast and needs water sooner than peat or potting soil.
• Temperature and humidity: a 78 F room at 40 percent humidity pulls water out fast. A cool, humid dome slows the loss.
• Airflow: a fan on low dries the surface without drying the root zone.
• Light: strong light drives transpiration and shortens the gap between waterings.

Prerequisites

• Container with drainage holes
• Water at 68 to 75 F
• pH 6.0 to 6.5 in soil, 5.8 to 6.2 in coco
• Plain water for week one. Quarter strength nutrients from week two if you grow in coco
• A syringe, squeeze bottle, or small measuring cup

Step-by-Step Watering Routine

1. Press a finger or moisture meter half an inch into the medium next to the stem.
2. Lift the container and judge its weight. A dry starter cup weighs almost nothing.
3. Skip the watering if medium still clings to your finger.
4. Draw 5 to 15 ml of water into a syringe or squeeze bottle.
5. Apply the water in a ring two inches out from the stem, not on the stem itself.
6. Stop when the medium is evenly moist. In week one, do not water to runoff.
7. Wait 24 hours.
8. Repeat the finger check and the weight check before the next watering.
9. Increase the volume by about 5 ml every two days as new leaves appear.
10. Water to light runoff once day 10 to 14 arrives and roots fill the cup.

Sample 14-Day Schedule

• Days 1 to 3: 5 to 10 ml once, only when the surface is dry.
• Days 4 to 7: 10 to 20 ml every 1 to 2 days. Check daily.
• Days 8 to 10: 20 to 30 ml every 1 to 2 days.
• Days 11 to 14: 30 to 50 ml every 1 to 2 days, with light runoff.
• Week 2 nutrients: quarter strength feed in coco, plain water in amended soil.

Treat these numbers as starting points, not rules. A hot tent can cut the interval in half. A cool, humid dome can double it.

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Signs of Overwatering

• Leaves droop and stay drooped after a watering
• Lower leaves yellow while the stem stays green
• Surface algae, fungus gnats, or a sour smell from the medium
• Soft, dark stem base that points to damping off
• Growth stalls for several days

Signs of Underwatering

• Medium shrinks and pulls away from the container wall
• Leaves curl upward or feel crisp at the edges
• The cup is feather light and the plant droops, then recovers after a drink
• Roots at the drainage holes look dry and pale

Common Mistakes

• Watering on a fixed clock instead of checking the medium
• Misting leaves, which invites mold and light burn
• One big soak followed by a long dry stretch
• Cold tap water straight from the line, which shocks young roots
• Feeding full strength nutrients before week three

When to Move Up

By day 14 to 21, most seedlings drink the starter cup dry in under a day. That is the signal to transplant into a larger container and switch to a soak and dry cycle, where you water until runoff and then wait for the pot to lose most of its weight before watering again.

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