Watering cannabis: Best practices to boost your grow

Watering cannabis is not just about turning on the tap and hoping for the best.

Watering is a crucial factor that can significantly impact your plants' health, growth, and yield. 

In this guide, we'll explore the best practices for watering cannabis. We’ll cover how factors like the growing medium, plant size, pot size, and the technology you have available affect your cannabis watering routine. 

We’ll also look at how cannabis growers can use stress techniques like dry backs to manipulate plant growth and explore the benefits of different cannabis watering systems.

By the end, you’ll have a clear understanding of how to water your cannabis plants effectively, no matter your style or setup.

Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis, you’re doing so by the law and subject to appropriate permissions and licenses of the applicable country.

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Factors that affect watering cannabis plants

Watering cannabis indoors isn’t a one-size-fits-all situation; several factors can influence how, when, and how much you need to be watering your cannabis plants. 

Let’s break down the key variables:

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1. Pot size

The size of your pot plays a massive role in your watering routine. 

Here’s the general rule: smaller pots require more frequent watering, while larger pots hold more water and therefore need watering less often.

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Big plant, small pot

If you’re growing a large plant in a small pot, you may need to water cannabis 10-15 times a day to keep up with its water and nutrient needs. 

Small pots dry out quickly, especially if the plant is large and consuming water rapidly.

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Small plant, big pot

On the flip side, if you have a small plant in a large pot, you might only need to water once a week. 

The larger pot holds more water, but the downside is that the soil may stay wet for too long, which can make it easier to overwater and harder for the plant's roots to access oxygen.

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2. The size of your plants 

A larger cannabis plant consumes 3 - 7 litres of water per day. Large plants typically need more water because they have more extensive plant roots and greater leaf mass.  

However, a larger plant also usually means a bigger pot, which can affect how frequently you need to water.

If you have a very large plant, it's generally a good idea to use a larger pot.

A large plant in a small pot may require constant watering to support vigorous cannabis growth, which can be hard to keep up with and may cause nutrient imbalances.

For smaller plants, a bigger pot isn't always ideal. 

Larger pots are harder to move, can get heavy, and they don’t dry back as quickly, which can limit oxygen flow to the roots—a crucial part of the watering process.

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3. Growing medium

The type of medium you’re using when growing cannabis indoors has a significant impact on your watering practices. 

Let’s take a closer look at three common mediums: soil, coco, and rockwool.

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Soil

Soil holds water well, which means it usually requires watering less often. 

However, it also takes longer to dry out, which can lead to overwatering if you’re not careful. 

If you’re growing cannabis plants in soil without additional nutrients, you might need a bigger pot, as the pot size acts like a battery or reserve of food for the plant. 

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Coco coir

Coco holds less water than soil but retains more air, making it more challenging to overwater. 

It tends to dry back more quickly, which helps get more oxygen to the roots and can promote faster growth. 

You can water coco more frequently—up to 10-15 times per day—especially with a good irrigation controller.

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Rockwool

Rockwool is even more extreme in its water-holding capacity than coco. 

It holds less water and requires watering more often, often demanding a reliable automatic watering system for cannabis to ensure the roots get consistent access to water and nutrients.

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4. Growing style 

Your growing style also determines your watering needs. 

If you’re using a natural or organic approach, you might be more hands-on, observing and adjusting as needed. 

If you’re running a high-tech setup with automation, your cannabis watering schedule can be much more regimented.

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5. Plant growth stage

Cannabis plants don’t have a one-size-fits-all watering need.

Their requirements vary significantly from the early stages of seedling growth stage through to the vegetative and blooming phases.

Let’s break down each stage:

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Seedling stage

Young cannabis plants are delicate. At this stage, they have smaller root systems that require frequent but light watering. 

You want to keep the top layer of your growing medium consistently moist but not soaked during the early stages. 

Overwatering younger plants at this stage can easily cause root rot or damping-off, a fungal disease that can wipe out seedlings fast.

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Vegetative stage  

As your plants mature and enter the vegetative growth stage, their roots grow deeper and wider, allowing them to uptake more water and nutrients.  

Water cannabis plants more deeply but less frequently during this period. 

Ensure the top inch or so of soil dries out before watering again. This encourages the roots to grow deeper in search of water, resulting in a stronger root system. 

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Flowering stage

During flowering, your cannabis plants will focus their energy on producing buds. 

You might decrease the frequency of watering slightly, but the amount of water per session may increase to ensure the roots are adequately hydrated. 

Avoid overwatering during this stage, as excess water can slow down flower development and promote mould growth.

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6. Environmental factors 

The routine for watering your cannabis plants should also consider environmental conditions like temperature, humidity, and light levels.  

For example, plants in humid environmental conditions may require less frequent watering than those in a drier climate.  

Also, cold water can shock your plants, so always use water at room temperature.

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7. Available technology

The technology you have available will also dictate your watering practices. 

From hand watering to advanced automated systems, the tools you use can simplify or complicate your routine.

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How to water cannabis plants: Proper watering practices 

Now that we’ve covered the factors that affect watering, let's dive into some best practices for proper watering tailored to different scenarios.

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Hand watering: The traditional approach

Hand watering your cannabis plants is great if you have a low plant count or if you’re growing big plants that don’t need constant watering. 

‍Perfect for those who want to connect with their plants and learn the nuances of their watering needs. 

Watering by hand allows you to monitor your plants closely and adjust based on their feedback.

• When to hand water cannabis: It is ideal for soil grows, small-scale setups, or growing larger plants in large pots.
• Tips for hand watering: Water slowly and evenly to allow the water to penetrate the soil thoroughly. Water early in the day to reduce evaporation and prevent fungal growth.

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Automated irrigation systems: Set and forget

If you’re growing in smaller pots with mediums like coco or rockwool, you’ll likely need an irrigation system or an automatic watering system for cannabis.

This can help maintain a consistent cannabis watering schedule. 

Digital timers, drip irrigation systems, automated fertigation systems and cannabis auto watering systems can be set up to water cannabis multiple times daily.

They are designed to deliver precise amounts of water at set intervals, reducing the risk of overwatering or underwatering and ensuring your plants stay hydrated without you needing to water them constantly manually.

• When to use automation: Best for medium to large-scale setups or when growing in fast-draining mediums like coco or rockwool.
• Benefits of automated systems: They reduce labour, ensure consistency, and allow you to step away from your garden for days without worrying about watering. They are perfect for delivering water frequently and ensuring consistent dry backs.

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Using stress techniques: Dry backs for faster growth

Dry backs are an advanced technique where you allow the growing medium to dry out more than usual between watering. 

This sends a stress signal to the plant, causing it to think it's in danger. If timed correctly, this can speed up flowering.

• How to use dry backs: Water less frequently but at higher volumes, allowing the medium to dry out completely before the next watering. Use this technique during the first 3 weeks of flowering to speed up flower formation and increase bud sites.
• Benefits of dry backs: Encourages deeper root growth, increases trichome production, and can shorten the flowering cycle.

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Choosing the right technology for your grow style

There’s a lot of good tech on the market to help growers manage their watering. Here are a few options:

• Digital timers: These can be set to turn on multiple times daily, ensuring regular watering.
• Irrigation kits: Kits with drippers, pipes, and pumps can make watering simpler and more efficient.
• Advanced controllers: These systems can automatically monitor soil moisture levels and adjust watering schedules. 

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Keep in mind that the right technology for you will depend on your growing style, the size of your plants, pot size, and medium.

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Watering cannabis in different mediums: Specific tips

Let’s go deeper into how watering practices change depending on your growing medium.

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Watering in soil

Soil retains moisture well, which means less frequent watering is required.

However, it also holds more water, which can increase the risk of overwatering. Here’s how to water cannabis grown in soil:

• Watering frequency: Usually every 3-7 days, depending on the size of your plants and environmental conditions.
• Signs to watch for: Overwatered soil plants often have yellowing leaves, drooping, and slow growth because of poor oxygenation.
• Tips for success: Use pots with drainage holes and water until you see runoff. Allow the top inch or so of soil to dry out before watering again.

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Watering in coco coir

Coco is great for growers looking for faster growth and more oxygen to the roots. However, it requires watering more often.

• Watering frequency: Depending on pot size and plant needs, it can range from several times a day (up to 15 times) to once every other day.
• Why It works: Coco retains air even when fully saturated, promoting root health and reducing the risk of overwatering.
• Tips for success: Use an irrigation controller for consistent watering. Check the weight of your pots to gauge when to water.

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Watering in rockwool

Rockwool is similar to coco but requires even more frequent watering because of its lower water retention.

• Watering frequency: Usually 10-15 times per day.
• Why It works: Rockwool holds less water, requiring frequent irrigation but providing excellent oxygenation to the roots.
• Tips for success: Use an automated irrigation system or drip irrigation systems to maintain consistent watering. Monitor plants closely for signs of stress, as Rockwool can dry out quickly.

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How dry backs influence plant growth: A deeper look

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What are dry backs?

A dry back is the period when the growing medium dries out between watering events. 

This period can be strategically used to stress your plants and induce hormonal changes that encourage faster flowering and higher-quality buds.

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Using dry backs to your advantage

When you let the medium dry back to the point where the pot feels light, the plant experiences mild stress. 

This can signal the plant to speed up its flowering process, thinking it needs to reproduce before it dies. 

However, this technique should be used carefully to avoid over-stressing the plant.

• When to use dry backs: Best used during the flowering stage, particularly in weeks 1-3.
• How to implement dry backs: Adjust your watering schedule to allow for longer periods between watering. Monitor the weight of your pots and the condition of your plants closely.

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Benefits and risks of dry backs

• Benefits: Can speed up flowering, increase bud sites, and enhance trichome production.
• Risks: If overdone, it can cause nutrient lockout, wilting, and reduced yields.

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Leveraging technology for consistent watering

Automated watering systems have revolutionised cannabis cultivation, making it easier to maintain consistent watering schedules and avoid common mistakes like overwatering or underwatering.

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Types of watering technology

• Hand watering tools: Watering cans and hose attachments for manual watering.
• Digital timers: Ideal for growers using drip irrigation or automated systems.
• Irrigation controllers: Advanced systems that monitor moisture levels and adjust watering schedules based on real-time data.

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Choosing the right tools for your grow

The best tool for you will depend on the number of plants you have, the medium you’re growing in, and your level of experience. 

Watering by hand is great for small grows, while automated systems are ideal for larger operations or when using fast-draining mediums like coco or rockwool.

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Ways of creating a customised watering schedule

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Observing your plants

Pay attention to how quickly your growing medium dries out, how your plants respond to watering, and any environmental changes, such as temperature or humidity shifts. 

Use this information to adjust how frequently you water.

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Using a baseline schedule

Start with a basic schedule:

• Soil: Water every 3-7 days.

Coco/Rockwool: Water multiple times a day, depending on the size of your plants and pot size.

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Monitoring soil moisture

Regularly monitoring soil moisture is key to avoiding both under watering cannabis symptoms and over watering cannabis symptoms. 

Use tools like moisture meters to ensure that your soil has the right level of moisture. 

This will help you create a more effective schedule for watering and improve your overall growing conditions.

The Grow soil probe goes beyond simply measuring soil moisture; it's a versatile tool that can elevate your cultivation strategy. 

Recording and analysing historical moisture data helps you identify patterns in water absorption, enabling you to make informed adjustments and optimise your watering practices for future grows.

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Fine-tuning your schedule

Make small adjustments based on plant feedback. If leaves begin to droop, you may need to water more frequently. If you notice yellowing leaves, you might be overwatering.

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Using a journal or app

Track your watering schedule, plant growth, and any changes you make. This can help you refine your routine over time and catch any problems early.

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One final note

The quality of water you use is crucial for maintaining plant health and maximising nutrient uptake. 

Poor water quality, such as water with high chlorine content or contaminants, can lead to nutrient deficiencies or damage beneficial bacteria in the soil. 

When using tap water, let it sit for 24 hours to allow chlorine to dissipate, which can harm your plants. 

To maintain good water quality, consider using filtered or distilled water, especially if you notice signs of nutrient lockout or plant stress.

Ensure there is proper water runoff from your pots when growing in coco or rockwool to prevent salt buildup and excess water retention that could damage the root system.

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Takeaways

Watering cannabis is not an exact science. 

From understanding the impact of pot size, plant size, growing medium and environmental factors to leveraging technology and using stress techniques like dry backs, there’s a lot to consider.  

But don’t worry—mastering your watering game comes down to observing your plants, adjusting as needed, and finding the right balance for your unique grow.

Remember, there’s no one “right” approach. The best strategy is the one that works for your situation. 

So, experiment, learn from your plants, and enjoy the process. If you need more guidance or have specific questions, feel free to reach out—we're here to help you grow the best!

Happy growing! 

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FAQs

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Should you water cannabis plants from the top or bottom?

When watering cannabis plants, it’s generally best to water from the top to ensure even moisture distribution and proper nutrient uptake. 

Top watering allows the water to flow through the growing medium, delivering nutrients directly to the root zone and helping flush out any excess salts or build-up that could cause nutrient lockout.

However, bottom watering can be useful in specific situations, like for young seedlings or small plants, to encourage deeper root growth.

It involves placing the pot in a shallow tray of water, allowing the plant to "wick" up the water from the base. This method can help avoid overwatering cannabis plants and promote healthy root systems.

Ultimately, choosing top or bottom watering depends on your growing style, the size of your plants, and medium. Experiment to find what works best for your cannabis cultivation!

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Is my cannabis plant overwatered? 

To determine if cannabis plants are overwatered, look for common signs like yellowing leaves, drooping, slow growth, and a mushy or dark appearance in the root system. 

Overwatered cannabis plants often have leaves that turn yellow and feel heavy or swollen. 

Check if the soil is consistently wet, even when the top layer should be dry, or if excessive water drains poorly from the pot.

If you notice these symptoms, adjust your watering frequency, ensure the pot has adequate drainage holes, and allow the growing medium to dry back more between watering sessions to avoid overwatering cannabis plants and potential root rot. 

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How long does it take for plants to recover from overwatering?

Recovery time for overwatered cannabis plants depends on the severity of the overwatering and the plant's overall health. 

Generally, plants can take a few days to a couple of weeks to bounce back after adjusting the watering routine. 

Ensure proper drainage, allow the growing medium to dry out, and avoid excessively watering during this period. 

Monitor for signs of improvement, like perkier leaves and new growth, to gauge recovery progress.

Keep the root zone well-aerated and consider using moisture meters and grow room sensors to help prevent overwatering, a humid environment, and root rot in the future. 

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What does cannabis look like when it needs water?

When cannabis plants need water, they often show signs like wilting or drooping leaves that appear limp and feel dry or brittle to the touch. 

The leaves might be dark green, curl inward or downward, and the overall plant may look less vibrant. 

If the soil feels dry an inch deep or the pot is light when lifted, these are indicators that your cannabis plant needs water.

To keep your cannabis plants hydrated properly, maintain a consistent watering schedule and monitor soil moisture levels regularly.

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Can plants recover from underwatering

Yes, cannabis plants can recover from underwatering if caught early. Wilted, dry, and curled leaves are signs of underwatering. 

To help them recover, water plants thoroughly and ensure the growing medium retains consistent moisture levels without becoming excessively dry.

Monitor soil moisture regularly and adjust your watering sessions to prevent underwatering cannabis in the future. This will ensure adequate hydration and promote healthy plant growth.`

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