A complete guide to watering cannabis plants

What’s the secret to thriving cannabis plants? It’s all in the watering. 

Watering your cannabis plants the right way means carefully adjusting the frequency and amount of water they get based on their growth stage, environmental conditions, and health. 

Growers should start with light, frequent watering for seedlings and gradually increase as the plants grow.

Check the pH of your water with a meter. In addition, use an RO (Reverse Osmosis) filter to remove any adulterants like heavy metals before watering. This can help create the perfect growing conditions for your plants. Also, avoid heavy metals leaching into the cannabis, as these are unsafe for consumption.

This guide walks you through the exact process of watering your plants from their tiny seedling stage to the final harvest. Follow the week-by-week watering instructions to ensure a great harvest.

• For watering seedlings, lightly moisten the substrate and monitor it daily to avoid overwatering or overly drying out.
• Volume and frequency of watering will depend very much on the substrate, drainage, ambient temperature, and cultivar.
• Water slowly and deeply, and since roots seek out water, focus on the outer edges of the pot to train the root ball to create a healthier, more widespread rhizosphere.
• Allow the top 1-2 inches of soil to dry between waterings to prevent overwatering and root rot.
• Adjust watering frequency and amount based on temperature, humidity, and growth stage. In summer heat, monitor the substrate more frequently to avoid overly drying out.

Cannabis plants can take up to 13 weeks from seed to harvest, although this depends greatly on the strain and growing conditions. 

The cannabis growth cycle includes the following stages: germination, seedling, vegetative, pre-flowering, flowering, and harvesting. 

Each stage has different watering requirements. Let’s break it down.

Seedlings are fragile. They need enough water to stay hydrated, but not so much that they get waterlogged. 

You’ll need a careful balance. If the water’s too much, your plants can get root rot, while too little dries them out.

The idea is to keep the soil consistently moist without drowning the plants.

Watering Guidelines:

• Frequency: Water lightly every 1-2 days. Seedlings need frequent, light watering to keep the soil moist without becoming waterlogged​.
• Quantity of Water: Around 10-20 milliliters per seedling should do the trick. You can use a spray bottle to mist the soil. You want to keep it moist but not soaked.
• Technique: Gently spray the base of the seedlings to avoid washing away the soil.
• Soil Moisture Level: Keep the top 1 inch of soil consistently moist. Studies show maintaining a moist soil surface helps seedlings develop a strong root system without the risk of root rot​​.

Precautions:

• Avoid Overwatering: Damping-off is a pathogen-borne disease that kills seedlings and is caused by overwatering. To avoid this disease, create good drainage.
• Monitor The Grow Room’s Temperature and Air Humidity: Growers report ideal humidity levels between 65% and 70%. This helps the seedlings stay moist without getting overwatered. 

A Quick Summary of Weekly Activities

Your seedlings made it through those crucial first two weeks. Now, they’re right into the early vegetative stage, marked by increased photosynthesis and nutrient uptake. Your plants start to grow, and their watering needs change.

Activities: Your cannabis plants begin to develop more leaves and a stronger root system. They need more water to support this rapid growth, support the larger leaf surface area, and increase metabolic activity​.

Guidelines

The rule of thumb is to water every 2 to 3 days. Stepping up the frequency is necessary to meet the higher water demand from the expanding root system and foliage.

• Technique: Focus on the outer edges of the pot to encourage the roots to spread, training the root ball. Use a watering can to get water into the entire surface of the substrate.
• Water Amount: Experienced growers recommend increasing water amounts in this early vegetative stage. The exact amount of water varies based on many variables such as plant size and environmental conditions, but a general guideline is watering about 25 to 30% of the volume of the pot.
• For example, a 5-gallon pot can take about 1.5 gallons of water.
• Water until the substrate is fully saturated and runoff appears. This would keep the soil moist to a depth of about 2 inches, which is critical for root development.
• Soil Moisture Level: The soil should be moist but not soggy. The next watering will be when the top few inches of substrate is dry. 

Precautions:

• If you don’t allow your substrate to dry out in between waterings, you risk overwatering which will prevent oxygen from reaching the roots.
• The outcome? Rotten roots. Make sure the drainage in your pots is adequate.
• Check Soil Regularly: Check the soil regularly by inserting your finger about an inch deep. If it feels dry, it’s time to water. If it’s still damp, hold off for a day.
• You can also lift the pot to get an idea of the ideal weight. If it’s too heavy, there might be too much water in the substrate.

Summary Table:

Your plants are now in the mid-vegetative stage, and they’re growing pretty fast! They’re now developing a robust structure to support future buds. 

The cannabis plants' root systems are expanding rapidly, and they need more water to support this growth. The leaves and stems are also growing quickly, and as you would imagine, the water demand increases.

Here’s how to make sure the plants get the water they need.

Watering Guidelines:

• Frequency: Do it every 2-3 days. Ensure that the soil remains moist but not soggy.
• Amount: Provide about 300-500 milliliters per plant per watering. This increase accounts for the larger root and leaf systems which need more water to stay healthy​.
• Technique: Water along the edges of the pot slowly and evenly to ensure moisture reaches the entire root system. 

Bonus tip:

Check the soil as often as you can: Again, dip your finger about 1 inch into the soil. If it feels dry, it’s time to water. If it's still damp, wait for another day.

Table:

Your cannabis plants are set up for flowering. The need for water continues to increase.

They still need plenty of water to support their growing structure and root systems.

Keep watering as often as you can to maintain cell turgidity and facilitate nutrient uptake. Turgidity and nutrient uptake remain essential for proper plant growth.

Guidelines for Growers:

Water as needed. Some cultivars might need daily watering or even multiple times a day.

• Amount: Water enough to keep the top inch of substrate moist but not soaking wet. As a general rule, the plant will need about 25 to 30% of the pot’s volume.
• Technique: Water slowly and, of course, deeply so water can penetrate the lower roots.

Precautions:

• Look out for pests and diseases: Pests might start to show up right about now. Take preventative measures against pests throughout the early vegetative stage and keep an eye on your plants for any signs of trouble.
• Think about proper drainage: Excess water should drain away to prevent root rot. Check your pots or ground conditions to ensure they’re draining well.

Table:

Great! Your cannabis has made it to the early flowering stage. This is an exciting time as you'll start to see the first signs of bud development. Watering becomes even more critical now to ensure those buds develop properly.

Proper hydration ensures nutrients are moved effectively throughout the plant​​.

Guidelines for Growers:

• Frequency: Keep watering every 2-3 days.
• Amount: Around 500-700 milliliters per plant per watering should suffice.
• Technique: Water deeply but ensure the soil has good drainage. New issues like mold and mildew can emerge from overwatering.

Precautions:

• How to reduce the risks of mold and mildew: Keep good airflow around the plants and avoid getting water on the buds. You’ll also need proper spacing and ventilation.
• Watch for signs of nutrient deficiencies or overwatering, such as wilting and brown spots, and adjust your watering schedule accordingly.
  

Table:

Your plants are now in the thick of flowering. Those buds are getting bigger by the day.

The need for a steady amount of water to support bud growth and resin production remains. However, the risk of mold increases if the temperature is too warm. You’ll need to monitor the soil moisture closely.

Our Guidelines for Growers:

• Frequency: Stick to watering every 2-3 days, adjusting intervals based on humidity and soil conditions.
• Amount: Somewhere between 500-600 milliliters per plant per watering does it. The amount can change based on factors like humidity, temperature, and environmental conditions.
• Technique: Again, water deeply, but ensure the soil drains well to prevent water from pooling around the roots.

Precautions:

Check the soil moisture as often as possible. Insert your finger about 2 inches into the soil. Only water if it feels dry.

You’re almost there. The buds are fattening up, and it’s almost time to harvest. This stage requires careful attention to watering to ensure a successful finish.

The watering needs may slightly decrease as the plants finish their life cycle.

Scientific Explanation: As the plants near the end of their flowering stage, they require less water because their metabolic activities slow down. They start to focus more on resin production and less on growth​.

Our Guidelines for Growers:

• Frequency: Stretch it out. Go for water every 3-4 days. Slightly reduce the frequency to prepare the plants for harvest.
• Amount: Provide 400-500 milliliters per plant per watering. Aim for 400–500 milliliters per plant for each watering. Since mold is an issue, this reduction in water quantity helps keep mold at bay and promotes the last phases of bud development.
• Soil Moisture Level: Keep the soil moist but not overly wet. Allow the top 3-4 inches to dry out more between waterings.

Precautions:

• Be careful with overhydration: Too much water at this stage can lead to mould and mildew. Ensure proper ventilation and drainage.
• Prepare for flushing: About two weeks before harvest, start flushing your plants with plain water to remove any excess nutrients, improving the taste and quality of the buds.

Table:

Another key consideration often overlooked in discussions about plant care is feeding, which involves watering plants with a nutrient solution. This is particularly crucial for growers, as nutrient-enriched water is essential for healthy plant growth. 

For instance, in many indoor grow setups, plants are fed with nutrient solutions every time they are watered, except during flushing periods. Feeding schedules can vary, but some growers feed their plants 4–6 times daily throughout their lifecycle. 

Incorporating nutrients into the watering routine ensures plants receive the essential minerals they need for robust growth, improved yield, and stress resistance, making it a vital part of plant care instructions.

Not all of us cultivate our cannabis in greenhouses indoors. When it comes to watering, what then can you do as an outdoor producer when the weather isn't suitable for your cannabis plant?  

Let’s start with solutions for the outdoor summer period.

Summer heat can be tough on your cannabis plants. With higher temperatures come increased risks of dehydration and heat stress. Your plants will need more water with hotter weather.

Here’s how to adjust your watering schedule to keep your plants happy and healthy.

• Water more often: But with the same or slightly less amount each time to prevent waterlogging.
• Water early mornings or late evenings: To reduce evaporation and help the plants retain moisture.
• Mulch: Use mulch around the base of the plants to retain soil moisture and maintain a stable soil temperature.

A lot can go wrong with watering your cannabis plants. Here are the most common problems we’ve identified and solutions to help you grow your plants.

Overwatering can lead to multiple problems, including stunted growth and harm to plants’ health. Here’s how to identify and fix an overwatering problem.

Symptoms:

• Yellowing Leaves: Roots are suffocating and can’t take up nutrients properly. That’s an urgent problem.
• Root rot occurs when the soil remains too wet. This fungal disease makes roots brown and mushy, preventing the plant from absorbing water and nutrients.
• Slow Stunted Growth: They may also develop droopy leaves that look lifeless.
  

Solutions:

• Give the soil time to dry out between waterings. This allows the roots to breathe, which helps prevent fungal diseases.
• Improve Drainage: Use well-draining soil and pots with drainage holes. Adding perlite or vermiculite to your soil mix can also help improve drainage.
• Water less often: Adjust your watering schedule to less frequent but more thorough waterings. Water deeply, and then wait until the top few inches of the soil are dry before watering agai.

Summary Table:

Underwatering can also be detrimental, leading to dehydration and nutrient deficiencies. Recognizing the signs early can help you take corrective action.

Symptoms:

• Your plants are wilting. The leaves will droop and look lifeless because the plant cells don’t have enough water to maintain their structure.
• The soil is too try. If the topsoil feels dry to the touch and pulls away from the edges of the pot, it’s a clear sign of underwatering.
• Plant growth is sluggish. Like overwatering, underwatering can also slow down plant growth. The leaves may become dry and brittle, and the plant may struggle to develop new foliage.

Solutions:

• Water more often: Water your plants more frequently. Monitor the soil moisture regularly. Water when the top inch feels dry.
• Keep the soil moisture even: Water thoroughly so that water can reach the roots. But then, avoid letting the soil stay constantly wet.
• Water deeply: When you water, do it thoroughly. Water until you see it draining out of the bottom of the pot, ensuring the entire root system gets hydrated.

Summary:

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