Learn all about cannabis watering and how to prevent common problems like over watering cannabis in SunMed’s comprehensive guide.

Everything You Need to Know About Cannabis Watering

Whether you're a seasoned cultivator or a novice green thumb, you might wonder how to maintain the health of your cannabis plants with the right amount of water. In this guide, we’ll discuss how to keep your plants healthy and hydrated, as well as how to prevent common problems that can arise when it comes to cannabis watering.

Why is Proper Watering Important for Growing Cannabis Plants?

Water plays a pivotal role in the life cycle of cannabis plants, serving as a conduit for essential nutrients and facilitating crucial processes like photosynthesis. Adequate hydration supports nutrient uptake, promotes cell expansion, and maintains turgor pressure. 

How to Properly Water Cannabis Plants

The best way to water cannabis is to check the soil for dryness and water as needed (rather than setting a schedule). Use your finger to see if the top inch of the soil or growing medium feels dry. If the top inch of the growing medium still feels moist, wait a day or two to water. If it’s dry, it’s time to water.

When you water, ensure the soil becomes moist, but not soggy. Maintaining an evenly-moist soil is key. Make a record of your watering schedule in order to better predict when your plants will need water in the future. Watering needs are based on your plant’s size and environmental conditions including indoor versus outdoor cultivation and humidity levels. That means it’s better to identify the plant's needs by tracking them rather than imposing a schedule. 

How Often Does Cannabis Need Watering?

In most cases, you will likely water container-grown cannabis plants every 2-3 days. Plants grown in soil will often need water at least once a day or more. However, it’s more important to test the dryness of the soil with your finger. If the soil is still moist, wait a day or two. As your plants grow, notice how long it takes for the soil to dry between watering sessions: in container growing, if the soil is still wet after 4-5 days, you likely need better drainage.

Remember, the frequency of cannabis watering depends on various factors, including plant size, stage of growth, and environmental conditions, such as indoor versus outdoor cultivation, light source, humidity, temperature, and more. 

How to Tell if a Cannabis Plant Needs Water

If the soil feels dry an inch deep and the leaves appear droopy or slightly wilted, it's likely time for watering. If the leaves become brittle and dry, it is definitely time to water; consider increasing the frequency of your watering sessions. 

Man holding a notepad and touching the growing soil in an outdoor plot

When is the Best Time to Water Cannabis Plants?

Watering cannabis plants in the morning allows them to absorb moisture before the day's peak heat, reducing the risk of fungal issues. 

How Much Water Does Cannabis Need?

The water requirements of cannabis vary throughout its life cycle. In general, provide enough water to saturate the root zone without causing waterlogged conditions. Each time you water, you want to give your plants a good soak, meaning around 25% of the container’s capacity. Aim for evenly moist conditions, but not “sopping wet.”

Fine tune your watering based on environmental conditions, growth phase, and growing medium. Read on to learn more about these factors.

Watering Cannabis Based on Grow Medium

The choice of growing medium can significantly influence watering practices. Some growing mediums offer great drainage, meaning overwatering/waterlogged roots won’t be an issue. For these mediums, you’ll need to check the moisture level and water more often. Other mediums retain water well, but therefore have the risk of low-drainage/overwatering. 

Find your chosen growing medium in the chart below to determine which issues you need to watch out for most when it comes to watering your cannabis plants.

Grow Medium

Watering Tips

Soil

Water only when the top inch is dry. Aim for thorough saturation without waterlogging. 

Coco Coir

Water only when the top inch is dry. This medium retains moisture well but requires proper aeration.

Peat Moss

Peat moss retains water effectively but can become compacted. Beware of waterlogging while maintaining consistent moisture levels.

Clay Pellets

Water and check moisture consistently. Clay pellets dry out quickly. 

Hydroponic

Requires precise, nutrient-infused water supply. Consistently monitor and adjust nutrient solutions.

Vermiculite

Water carefully to avoid waterlogging. Vermiculite retains moisture well.

Rock Wool

Water consistently. Rock wool provides excellent aeration, but doesn't retain water effectively. 

Perlite

Water consistently. Perlite is a well-draining medium with low water retention. 

How Does the Growth Stage of Cannabis Impact Its Watering Needs?

The growth stage profoundly influences cannabis watering requirements. In the early stages, seedlings prefer gentler hydration. Gradually increase water amount as plants mature. During flowering, water intake peaks. Explore the chart below for best practices for watering cannabis at different stages in the plant’s life cycle.

Growth Stage

Watering Tips

Germination

Begin with light misting to keep the growing medium consistently damp. As seedlings emerge, gradually increase water, but proceed with caution - overwatering at this phase can suffocate the new roots. Try to maintain damp, but not wet, soil conditions.

Propagation

Maintain a humid environment for clones, ensuring a consistent moisture balance. Gradual increases in water volume support root establishment, but again be cautious of overwatering to avoid waterlogged roots.

Vegetative Stage

During the vegetative stage, cannabis plants experience rapid growth and a surge in the amount of water needed. Increase watering amount. Let the top inch of the soil dry completely between waterings.

Flowering Stage

Continue watering consistently at this stage. Allow the top 1-2 inches of soil to dry completely between watering sessions. Overwatering at this phase can lead to moldy buds or diseased roots, so it’s better to under-water than overwater at this stage.

What Methods Can You Use to Determine if It’s Time to Water Cannabis?

There are several methods to help you gauge when to water your cannabis plants. The easiest of all might be “the finger test,” but we cover a few other options below so you can decide the best way to monitor your plants' moisture levels.

The Finger Test 

The finger test is a hands-on approach to assess soil moisture that will be familiar to gardeners of all stripes. To perform the finger test, insert your index finger into the soil up to the first knuckle. If it feels dry, it's time to water. If the soil feels damp, wait a day or two and test again.  

The Weighing Pots Method

For this method, lift up your plant’s container or pot to feel how heavy it is. If you perform this test regularly, you’ll get an intuitive sense of how heavy the pot feels when the plant needs water. A dry pot feels lighter than a watered one. 

Moisture Meters Method

Moisture meters provide a quantitative measure of soil moisture. SunMed Growers, leveraging technology in their Maryland greenhouse, utilizes these meters for precise readings. Insert the probe into the soil, and the meter indicates moisture levels. This method is preferred for growers looking to monitor moisture with more precision.

Soil moisture and PH sensor which used to create a cannabis watering schedule

What are Some Recommended Methods for Watering Cannabis?

Effective watering methods are crucial for cannabis health. Techniques such as bottom watering, drip irrigation, and hand watering with a gentle stream are recommended.

Bottom Watering

Bottom watering involves providing water directly to the root zone from below. This method encourages robust root development and prevents water contact with leaves, reducing the risk of fungal issues.

Spraying

Spraying, or foliar feeding, involves applying a fine mist of water directly onto the leaves. While it's not the primary method for hydration, it serves as a supplemental technique for nutrient absorption and is often preferred during the germination phase.

Hand Watering

Hand watering, a traditional method, involves manually applying water to the base of cannabis plants using a watering can or hose. This hands-on approach ensures a gentle stream for even moisture distribution and allows growers to closely monitor plant needs.

Wick System

The wick system utilizes capillary action to deliver water from a reservoir to the soil. Incorporating this method ensures a steady and controlled water supply. The wick system is particularly useful for small-scale setups, providing an automated yet simple solution for maintaining consistent soil moisture.

Drip Irrigation

Drip irrigation delivers water directly to the base of each cannabis plant through a system of tubes and emitters. Drip irrigation conserves water, minimizes soil compaction, and supports optimal nutrient absorption.

Soaker Hoses

Soaker hoses are porous hoses that release water directly into the soil along their length. Soaker hoses provide efficient and targeted watering. This method minimizes water wastage, prevents foliage contact, and promotes deep root hydration. This method is useful for outdoor grows in particular.

Ebb and Flow

The ebb and flow method, also known as the flood and drain system, alternates between flooding and draining the growing medium. This method enhances nutrient absorption and oxygenates the root zone. The controlled cycles of inundation and drainage promote vigorous cannabis growth.

SunMed's state of the art greenhouse uses advanced hydration sensors and irrigation technology

What Kind of Water is Best for Watering Cannabis?

  • pH-Balanced Water: Cannabis plants thrive in a slightly acidic to neutral pH range. Maintaining a pH-balanced water supply is crucial for preventing nutrient lockout, where essential minerals become unavailable to the plant.

  • Contaminant-Free Water: Cannabis plants are sensitive to contaminants, and impurities in water can adversely affect their health.

  • Low Mineral Content: Water with high mineral content, known as hard water, can lead to nutrient imbalances and salt buildup in the soil. 

  • Consideration of Water Source: Different water sources can vary in quality, so take the characteristics of your local water supply into consideration. Whether sourced from wells, municipal systems, or elsewhere, understanding the baseline qualities of the water you’re using will allow you to make needed adjustments for optimal cannabis cultivation.

What are Some Preventable Problems When Watering Cannabis? 

Overwatering, underwatering, nutrient imbalances, and poor drainage are common pitfalls when it comes to watering cannabis. In the following sections, we'll delve into preventive measures and troubleshooting techniques to avoid watering problems.

Over Watering Cannabis (Poor Drainage)

Overwatering, a common concern, leads to waterlogged soil, depriving roots of oxygen and causing root rot. Over watering can happen as a result of simply watering too much, but it is most often caused by watering on a reasonable schedule into a pot with poor drainage. The water cannot escape, leaving it to sit in the pot and potentially lead to health issues for the plant. 

Symptoms of overwatering include:

  • Drooping leaves

  • Yellowing leaves

  • Soil/growing medium staying “soaked” for days

  • Root rot

  • Fungus and other diseases

To avoid overwatering, always allow the top inch of soil/medium to dry out before rehydration. 

How to Reverse Over Watering 

To reverse overwatering, allow the soil to dry between waterings and lower watering frequency. Employ a gradual approach, ensuring the recovery of cannabis plants without causing additional stress. 

If you’ve cut back on your watering sessions but are still seeing symptoms of overwatering, be sure to check out what’s going on with your drainage. You can enhance drainage by adding perlite or coarse sand to your growing medium. Make sure the hole at the bottom of the pot is large enough for water to escape, and drill more holes or change pots if it isn’t. You should check to make sure that at least some water flows out from the pot after watering.

Under Watering Cannabis

Underwatering occurs when plants receive insufficient water. Symptoms of underwatering include:

  • Wilting leaves

  • Drooping leaves

  • Dry/brittle leaves

  • Slowed growth

  • Lifeless looking plants

Preventing underwatering involves maintaining a consistent watering schedule, monitoring soil moisture, and adjusting based on environmental factors. Thorough hydration during each growth stage is recommended to ensure plants receive adequate water. Regular observation and adaptation to changing conditions are crucial for preventing underhydration.

Many people do not water their plants deeply enough even though they water frequently. You want water to reach all the way to the bottom of the roots. We discussed bottom watering above, which is probably one of the most effective ways to water any potted plant, and is a very useful technique for people who struggle with under watering.

How to Reverse Under Watering

To reverse under watering, gradually increase watering frequency while monitoring soil moisture. Take a cautious approach to prevent shock. During each watering session, give the plant a good soak. Aim for moist but not wet conditions after each watering session.

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