Cannabis Watering Schedule: How Often to Water Cannabis

Quick answer

There is no fixed cannabis watering schedule. Water when the top 1 to 2 inches of soil are dry. In a 5-gallon pot, a flowering plant may drink 0.5 to 1 gallon every 1 to 2 days. A vegetative plant may drink every 2 to 3 days. Seedlings need 1 to 2 ounces every 2 to 3 days.

Cannabis Watering Schedule for Autoflower Plants: A Complete Guide

Check soil before you water

Stick a finger 2 inches into the soil. If it feels dry, water. If it feels moist, wait. A moisture meter reads 3 to 4 on a 1 to 10 scale before watering. Lift the pot. A dry pot feels light. A wet pot feels heavy.

read more

Water volume by pot size

• 1-gallon pot: 0.25 to 0.5 gallon
• 3-gallon pot: 0.5 to 0.75 gallon
• 5-gallon pot: 0.75 to 1 gallon
• 10-gallon pot: 1.5 to 2 gallons

Water until 10 to 20 percent of the volume runs out the bottom. This flushes salt buildup. Discard runoff. Do not let the pot sit in water.

Cannabis Watering Schedule for Seedlings

Watering by growth stage

Seedlings (week 1 to 2)

Roots are small. Water 1 to 2 ounces in a 6-inch circle around the stem. Wait 2 to 3 days. Use a spray bottle. Keep soil moist, not soaked.

Vegetative stage (week 3 to 8)

Plants grow fast. Water every 2 to 3 days in a 5-gallon pot. Increase volume as roots fill the pot. A 2-foot plant in a 5-gallon pot may drink 1 gallon every 3 days.

Flowering stage (week 9 to 14)

Buds need more water. Water every 1 to 2 days in a 5-gallon pot. A 4-foot plant may drink 1 gallon each day. Check soil twice per day in hot rooms. Temperature above 85°F and humidity below 40% speed water use.

Late flower and flush

Water with plain pH-adjusted water 7 to 14 days before harvest. Some growers stop water 2 to 3 days before harvest. This is optional. No data shows it increases potency.

Signs of overwatering and underwatering

• Overwatering: drooping leaves, yellow lower leaves, fungus gnats, stem rot
• Underwatering: dry crispy leaf edges, slow growth, pot feels light, soil pulls from pot sides

Overwatering kills more cannabis plants than underwatering. Roots need oxygen. Soggy soil blocks oxygen and causes root rot.

Water quality and pH

Soil pH should be 6.0 to 7.0. Water pH should be 6.0 to 6.5 for soil. Tap water with 150 to 300 ppm total dissolved solids works. Chlorine evaporates in 24 hours if you let a bucket sit. Chloramine does not evaporate. Use a carbon filter if your water has chloramine.

Tools

• Moisture meter: $10 to $20
• pH pen: $30 to $80
• Bucket with measurements: $5
• Saucer or drain tray: $3 to $10

Common mistakes

1. Watering on a fixed schedule. Check soil first.
2. Small sips every day. This keeps top soil wet and bottom soil dry. Water until runoff, then wait.
3. Letting pots sit in runoff. Empty saucers 30 minutes after watering.
4. Using cold water. Let water reach room temperature, 65 to 75°F.

Record keeping

Write the date, water volume, and pot weight. After 2 weeks you will see a pattern. Adjust for temperature and humidity. A 10°F rise in room temperature can double water use.