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Watering Cannabis Seedlings: Day by Day Schedule

watering cannabis seedlings

Watering cannabis seedlings is a critical aspect of their care, and getting it right can make a significant difference in their development. This article provides an overview of watering cannabis seedlings and a day-by-day schedule to ensure they receive the optimal amount of water.

Understanding Watering Cannabis Seedlings

Cannabis seedlings are particularly sensitive to their environment, and water plays a crucial role in their early development. They require consistent moisture but are susceptible to damage from too much water. The objective is to keep the soil moist but not soggy, allowing the roots to access both water and oxygen. Too much water might lead to root rot and other cannabis problems, while too little can cause dehydration and stunt growth.

The Role of Water in Cannabis Seedling Development

Water is a vital component of plant life, carrying essential nutrients from the soil to the plant cells. For cannabis seedlings, which are in the initial stages of growth, the balance of water is critical. Here’s why:

Enhanced nutrient mobility and soil structure

Water acts as a solvent, carrying dissolved nutrients to the roots. It facilitates the movement of essential elements like nitrogen ,potassium, and phosphorus, crucial for the early stages of plant development. Conversely, adequate moisture helps maintain soil structure, providing a stable environment for root growth. Water also helps bind soil particles into aggregates, which improves aeration and root penetration.

Support of cellular functions and plant rigidity

The turgor pressure created by water in the plant cells is essential for maintaining cell shape and firmness. This pressure allows the seedlings to stand upright and grow toward the light. Alternatively, most enzymes require a hydrated environment to function properly. Water facilitates enzymatic reactions that are vital for plant metabolism and growth.

Regulation of plant temperature and environmental stress

Through transpiration, water evaporates from the plant’s surface, cooling the plant. This is particularly important for seedlings under grow lights, which can generate significant heat. Conversely, adequate watering helps seedlings cope with environmental stresses such as high temperatures or dry air. It acts as a buffer, maintaining internal homeostasis.

Optimization of photosynthetic and respiratory processes

Water is a raw material in the photosynthetic reaction. Adequate hydration ensures that the photosynthetic process is efficient, leading to better energy production. Water also involves respiration, where cannabis plants release energy from sugars. Proper water supply ensures that respiration proceeds smoothly, providing energy for growth.

Creating a Watering Schedule for Cannabis Seedlings

Developing a watering schedule can help you track when to water your seedlings. Adjust the schedule based on the plant’s growth stage and the environmental conditions. Remember, the frequency of watering will change as the plant grows.

Day by day seedling watering

Here’s an expanded day-by-day watering schedule to ensure your cannabis seedlings receive the optimal amount of water:

Day 1-7: The First Week

  • Day 1: Water with 2 cups (500ml) per plant. This initial watering is crucial as the seedlings should have their leaves open and be under the grow light.
  • Day 3: Repeat with 2 cups (500ml) per plant. The soil should start to dry out slightly between waterings.
  • Day 6: Continue with 2 cups (500ml) per plant. Observe the cannabis seedlings for any signs of stress.

Day 8-14: Establishing a Routine

  • Day 8: Increase to 3 cups (750ml) per plant. This supports the growing needs of the seedlings.
  • Day 11: Maintain 3 cups (750ml) per plant. The cannabis seedlings should be showing robust growth by now.
  • Day 14: Upgrade to 4 cups (1 liter) per plant. The increased water supports the expanding root system.

Day 15-21: Monitoring and Adjusting

  • Day 17: Continue with 4 cups (1 liter) per plant. Watch for any changes in the seedlings’ appearance that might indicate over or underwatering.
  • Day 20: Provide 5 cups (1.25 liters) per plant. The seedlings are now entering a more vigorous growth phase.

Day 22-28: Preparing for Vegetative Stage

  • Day 23: Give 6 cups (1.5 liters) per plant. The larger volume compensates for the increased evaporation as the plants get bigger.
  • Day 26: Maintain 6 cups (1.5 liters) per plant. Ensure the watering reaches deep into the soil to encourage deep root growth.
  • Day 29: Increase to 8 cups or 1/2 gallon (2 liters) per plant. This prepares the seedlings for the upcoming vegetative stage, where water demand will rise.

Day 29 and Beyond: Adapting to Growth

After the first 30 days, continue giving 1/2 gallon (2 liters) per plant every 3 days. As the cannabis plants grow, they may require more water or more frequent watering. If the plants appear droopy before the scheduled watering, it’s a sign to adjust the amount or frequency.

Risks of Improper Cannabis Seedling Watering


Excessive water can suffocate the plant’s roots, preventing them from absorbing oxygen. This may lead to root rot, a condition where the roots turn brown and mushy. Also, overly damp conditions are ideal for the proliferation of fungi, which can infect the seedlings and lead to diseases like damping-off. In addition, too much water can cause nutrients to become unavailable to the cannabis plant, leading to deficiencies despite the presence of nutrients in the soil.

Prevention: To prevent overwatering, ensure your pots have adequate drainage holes, water only when the top inch of soil is dry, and use a potting mix that drains well.


Insufficient water can slow down the growth of seedlings as they struggle to perform basic functions like photosynthesis and nutrient uptake. Underwatered seedlings may also exhibit wilting, where leaves lose their rigidity, and crisping, where the edges of leaves become dry and brittle. Furthermore, prolonged dry conditions can cause the roots to dry out and die, which can be irreversible if not addressed quickly.

Prevention: Monitor the soil moisture regularly, establish a consistent watering schedule, and adjust based on the seedlings’ response and environmental conditions.

How To Determine Whether Your Cannabis Plant Is Overwatered or Underwatered

One of the most frustrating issues facing cannabis farmers is that overwatered and underwatered plants frequently display identical symptoms. Both overwatering and underwatering can cause drooping leaves and floppy stems. Picking up the container is the best way to evaluate whether your plant needs water. If it feels heavy, the plant probably has enough moisture. In contrast, if it seems very light, the plant usually needs more water. Another excellent way is to press your finger into the top layer of soil. The growth media should feel moist but not too damp or dry.

Preparing the Growth Medium for Cannabis Seedlings

Optimizing conditions for cannabis seedlings encourages healthy growth during the vegetative and flowering stages. The first step is to prepare your chosen media and use the most effective procedures.

Choosing the correct approaches

Light potting soil and rock wool cubes are the most popular media for germinating or housing seedlings. Both systems are wonderful when properly maintained. If you use soil, be sure you choose the right type. It must be light and free of pollutants or excess fertilizers that might harm delicate seedlings. The ideal soils for sprouts have an organic matter that retains moisture.

Watering weed seedlings

In addition, cannabis growers use porous materials such as perlite or vermiculite to help with drainage while watering cannabis seedlings. While both approaches are wonderful, rockwool has several advantages over soil. This substrate improves ventilation and water drainage for the growing root system.

Monitor and adjust the pH level

Acidity control is an important part of watering cannabis seedlings and overall production. pH values of 5.5-6.5 are typically appropriate, although this range might fluctuate based on various conditions. Some growing mediums perform well with more acidity, and the type of cannabis is another variable. Each cannabis strain requires distinct and particular conditions for maximum production. Alternatively, all commercial cultivars come with comprehensive instructions, and keeping the proper acidity level is critical. When you’ve determined the ideal pH for cannabis, keep track of measurements and modify as needed with solution products.

Properly moistening the growth medium

Pre-moistening the growing media is critical for germination and seedling growth. Water is required for growth, but too much can lead to molds and infections, damaging cannabis yield and quality. You are urged to maintain a moderately humid medium throughout the cannabis seedling’s development.

Monitoring Soil Moisture

 This is a critical aspect of cannabis seedlings, ensuring that your plants receive the right amount of water for optimal growth. Here’s additional information to enhance your understanding and techniques for monitoring soil moisture:

Advanced Techniques for Monitoring Soil Moisture

  1. Finger test: This traditional method involves inserting a finger into the cannabis soil up to the second knuckle. If the cannabis soil is dry at that depth, it’s time to water. If it feels damp, you should wait before adding more water.
  2. Soil moisture meters: These devices come with a probe that you insert into the soil. They provide a quantitative measure of the moisture level, helping you make more informed cannabis seedling watering decisions.
  3. Weighing the pot: You can gauge the pot’s water content by lifting it. A heavier pot indicates moist soil, while a lighter one suggests it’s time to water.
  4. Observation: Experienced growers often rely on visual cues from the cannabis seedling and soil and the overall environment to judge when to water.

Understanding the Indicators of Inadequate Moisture Levels

  • Yellowing leaves: Yellow leaves can signal both overwatering and underwatering. Checking the soil’s moisture can help determine the cause.
  • Limp or drooping leaves: Often a sign of overwatering, droopy leaves indicate that the roots may be deprived of oxygen.
  • Brittle or brown leaves: These symptoms suggest underwatering and severe dehydration.

Environmental Factors Affecting Soil Moisture

  • Humidity: Weed plants prefer a humidity range of 55-65%. High humidity means less water demand from the soil, while low humidity leads to more rapid transpiration.
  • Temperature: Higher temperatures can increase evaporation and transpiration rates, requiring more frequent watering.
  • Airflow: Good ventilation can help regulate soil moisture by preventing excess humidity and allowing the soil to breathe.

Best Practices for Soil Moisture Management

  1. Regular checks: Consistently monitor the soil moisture using a combination of methods to ensure accuracy.
  2. Adjust watering schedule: Be flexible with your watering schedule to accommodate changes in environmental conditions and plant needs.
  3. Proper drainage: Ensure your pots and soil have good drainage to prevent waterlogging.

Optimal Watering Techniques for Cannabis Seedlings

It’s important to follow best practices and ensure a healthy watering environment for your cannabis seedlings to promote strong growth and prevent issues. Here are some tips growers can use to water their cannabis seedlings effectively:

  1. Water quality: It’s not just about the quantity but also the water quality. Use filtered or distilled water, if possible, to avoid chlorine and other chemicals that can be harmful to young cannabis plants. If using tap water, let it sit out for 24 hours to allow chlorine to evaporate.
  2. Watering frequency: While a common recommendation is to water every few days, the actual frequency will depend on factors like humidity, temperature, and the growth stage of the seedlings. It’s crucial to monitor the soil and plants rather than sticking to a rigid schedule.
  3. Watering method: Besides using a spray bottle or gentle stream, consider bottom-watering. This method involves placing water in the tray beneath the pots, allowing the soil to absorb moisture from the bottom up. It encourages deep-root growth and can help prevent overwatering.
  4. Humidity levels: Cannabis seedlings thrive in higher humidity levels, around 65-70%. You can maintain this using a humidity dome or tray cover for the first week or two. This helps keep the cannabis soil moist and reduces the necessity for frequent watering.
  5. Avoiding contaminants: Be cautious of any fertilizers or pesticides you use in the early stages. Seedlings are sensitive, and harsh chemicals can damage them. Opt for organic, seedling-safe options if needed.
  6. Mulching: Applying a thin layer of mulch on the soil’s top can help retain moisture and regulate soil temperature. Organic mulches like straw or bark chips are also good options for cannabis seedlings since they add cannabis nutrients to the soil as they decompose.
  7. Observation and adjustment: The most important aspect of watering cannabis seedlings is observation. Look for signs of over or underwatering, such as yellowing or drooping leaves, and adjust your watering practices accordingly.
  8. Clean tools: Sanitize your watering cans, hose ends, and other tools regularly to prevent the spread of pathogens. You should use a solution of one part bleach to nine parts water for effective sterilization.

Correctly Watering Seedlings for Optimum Growth

A consistent watering schedule is essential for healthy cannabis seedlings. By following the guidelines above and observing your plants’ responses, you can ensure your seedlings develop into strong, healthy cannabis. Remember, the best watering practices adapt to the specific needs of your cannabis plants and growing conditions.

Picture of Ed Rushford

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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