The last time you may have heard the term pH was back in high school when you were wearing a lab coat and safety goggles and eagerly learning about the difference between acid, alkaline, and neutral using test tubes. If you want to adjust pH in your swimming pool, garden pond, or hydroponic system, it is essential to know why you are doing it and the correct steps and equipment required to do so.
It may sound like complicated science, but once you understand the logic behind it, it will make sense. Think of pH as the sweet spot all living things must adapt to. So get ready to learn about one of the most vital parts of growing cannabis, and find out how easy it is to keep your garden pH-perfect!
TL/DR | Key Takeaways:
The Ideal pH level for organic cannabis plants – 6.0 – 7.0 pH.
The ideal pH level for hydroponic cannabis plants – 5.5 – 6.5 pH.
An imbalance in pH can cause nutrient deficiency problems.
pH dictates the amount of available nutrients and how well the plant can absorb them.
Incorrect pH levels lead to stunted plants or very slow growth.
Yields can be significantly affected by pH levels and maintenance.
Use pH meters, test solutions, and test strips to check pH.
Tap water should be dechlorinated for 24 hours when adding pH up or down
It is best to dilute the pH up or down from a concentrated solution.
Testing the pH of the nutrient runoff is an important part of pH maintenance.
Always wear protective goggles and gloves, and work carefully.
What are the Symptoms of pH Imbalances in Your Cannabis Grow?
Materials And Tools to Adjust and Control pH in Your Cannabis Grow
Step 1: Allow Water to Dechlorinate & Reach Room Temperature
Step 4: Dilute pH Up / Down Solution Before Adding it to Your Water
Step 5: Slowly Add Pre-Diluted pH Up or pH Down Solution and Monitor
Maintaining Proper pH to Get that Sweet Spot for Your Plants
Testing Soil pH and Run-off Water pH to Avoid Nutrient Lockout
What Is pH?
PH stands for “the potential of hydrogen,” which, in practical terms, means that pH is a measurement of the acidity or alkalinity of a liquid. The pH measurement is based on a 14-point scale, with neutral representing the center point (pH 7). Below is a short list representing the full scale to give you an idea of different pH levels.
Why is pH Important in Cannabis Cultivation?
All the nutrients a cannabis plant needs during its lifecycle are accessible at a specific pH range. This covers the primary, secondary, and trace minerals. When it comes to growing cannabis, a slightly acidic medium is required. Aim for the sweet spot of 5.5-6.5 (hydroponic and soil).
Ideal pH range for growing marijuana
Cannabis plants rely on the correct pH levels to access different nutrients, as shown in the illustration above. The ideal levels account for the nutrient solution and the growing medium and are the difference between healthy, happy, perfectly growing plants and a stunted, low-yielding, and malnourished crop. Luckily, we have plenty of in-depth articles about all things pH. I recommend reading How to measure pH and PPM, The best pH and TDS levels, The best pH, EC, or TDS values for hydroponics, Things you should know about pH, and How pH affects cannabis seed germination.
What is the Ideal pH for Cannabis?
To keep things as simple as possible, all you need to remember is there will be one pH range for soil growers and another for hydroponic growers. Plants will shift their pH levels and drift between the optimal ranges, depending on which primary nutrients (N,P,K), secondary nutrients (Ca, Mg, and S), and trace elements are needed.
Ideal pH level for cannabis plants grown in soil – 6.0 – 7.0 pH
Ideal pH level for hydroponic cannabis systems- 5.5 – 6.5 pH
The Benefits of Maintaining the Perfect pH
Apart from growing head-turning, picture-perfect crops, maintaining optimal pH levels consistently has many benefits. These benefits range from promoting microbiological activity in the soil to optimum nutrient solubility and availability. Solubility and availability are basically another way of saying how easily the nutrients are dissolved in water when you make your nutrient solutions and how easily the plants can use them.
As a wise man once told me, “Think of growing cannabis as baking, where the ingredients must be mixed in precise amounts to achieve the perfect flavor and texture. In this scenario, the nutrients are your ingredients, and the pH level of your growing medium or nutrient solution is the oven temperature. Just as the temperature must be set just right to bake a cake—too high, and it burns; too low, and it’s undercooked—the pH level must be carefully adjusted to ensure the nutrients are accessible and well balanced!”
What are the Symptoms of pH Imbalances in Your Cannabis Grow?
As a beginner grower, pH may not be at the top of your priority list. Unfortunately, if you notice your once lush green plants beginning to show signs of deficiencies and slowly but surely losing vigor, there might be something wrong with your pH levels. That’s why it’s crucial, even for a beginner, to wrap your head around the art of maintaining your pH levels.
Here are a few signs to look out for when it comes to having your pH levels out of balance:
If pH levels are too low:
Nutrient burn/toxicity: tips of leaves turning yellow and brown
The leaves curling inwards
Leaves will turn dark green
Leaf showing signs of low pH imbalance issues.
If pH levels are too high:
Stunted plants or very slow growth
The leaves are turning yellow and brittle
The foliage will change to pale green
The leaf tips have a chemical burn look
Unhealthy leaves showing signs of high pH imbalance.
If any of these seem incredibly familiar, there is a good chance you have experienced a pH imbalance that sent things one way or another. Do not worry; the damage done can always be repaired. Cannabis plants will bounce back once the pH problem has been adjusted and you are back in control of nutrient availability.
Materials And Tools to Adjust and Control pH in Your Cannabis Grow
Before you get your white lab coat back out, order a chemistry set and test tubes, and relive your high school science classes, relax. Making a pH adjustment and controlling pH levels is not complicated. Below are a few options you can consider before making a purchase.
pH Meters, pH Test Solution, and pH Test Strips
Once calibrated, pH meters let you insert their pen into plain water or a nutrient solution mix and instantly see the pH level. I recommend a digital pH meter. You are trying to develop a habit, so the time saved compared to other methods, such as pH test solutions and pH test strips, will make your life much easier.
Example of a pH meter.
pH up / pH Down Solutions Commercially Available
Buying pH up or down will not break the bank, and once bought, it should last you several crops before needing to buy more. Check out Plagron’s pH control products if you want to bag yourself a top-quality solution. These liquid bottles will let you increase or lower the pH of your water/nutrient solution.
Plagron pH adjustment products.
Containers
You will use the small containers provided with pH up and down kits to take a test sample. This is basically the same way you would check the pH of a swimming pool once you have added the relevant amount of chlorine. Always make sure the containers are clean and dry before using them again.
Pipette
These are a small plastic apparatus that sucks liquid up into a tube using air pressure. The pipette will also have a measurement scale printed on it, making life easy when taking the exact measurement and administering the pH up or down in droplets.
Pipette for administering nutrient solution in cannabis cultivation.
Can I Use Vinegar or Other Household Items to pH Up/Down?
Peat moss is naturally acidic, so it can be used as an organic method to lower the pH of water. To do this, create a cold water extract and allow the peat to sit there for several or 24 hours, depending on the water source. You can also add Peat directly to an alkaline-rich growing medium, and it will naturally buffer over time.
Baking soda (sodium bicarbonate) and wood ash are alkaline, so they can be used to lower pH levels. If you are going down the homemade solution path, work with small amounts at a time and check how much the levels have adjusted.
Limestone contains calcium carbonate and is another way to increase water’s pH levels. It is relatively easy to find and can be bought from local garden centers or online. Check out Plagron’s Calcium Kick.
If there is no more pH up or down left in the country, and you have no other means, then you can use household items. I would not recommend it, but a bit of white vinegar or citrus juice would decrease pH levels. They are basically acetic acid and citric acid, after all. However, I recommend leaving lemon juice and white vinegar for cooking and peat or wood ash as organic amendments for regenerating soil or compost piles.
Safety Considerations
When using chemicals to adjust the pH levels, always wear gloves and cover your wrists and arms, as these can be irritant. Wear safety goggles and work carefully and meticulously to avoid spills or splashing. Keep your bottles of pH up and down in a cool and dark environment, and keep them out of the reach of children.
How to Use pH Up/ Down Solution in Water for Cannabis
You can use many types of water, ranging from reverse osmosis (RO), rainwater, distilled water, bottled water, and tap water (soft or hard). In this section we will look at the steps you have to take when adjusting the pH using tap water.
Step 1: Allow Water to Dechlorinate & Reach Room Temperature
Chlorine is alkaline, registering at 13 on the pH scale. To lower the pH to the sweet spot, fill a container and leave the water out for 24 hours to dechlorinate as the chlorine evaporates.
Step 2: Determine the pH of your Water
It is important to be fully aware of the pH level of the water source you are working with. Using your pH pen or pH testing kit, simply turn on the pen, dip the end in the water source, take a reading (meaning whatever the number on the pen is displayed), and record the figure in your grow journal.
pH meter placed in water.
Step 3: Add Nutrients to the Water Solution
This is where the fun starts! Even though adding bottled nutrients to the water may sound straightforward, it is important to stir well and thoroughly mix each time you add nutrients.
Step 4: Dilute pH Up / Down Solution Before Adding it to Your Water
The short and simple answer is to produce a nonconcentrated form that the acid or alkaline base can bond to, making the adjustment process easier and more controlled. The other reason is to avoid producing precipitates, slightly solid formations that occur from chemical reactions.
Precipitate settled in a water container.
Step 5: Slowly Add Pre-Diluted pH Up or pH Down Solution and Monitor
The trick now is to slowly add the pre-diluted pH up or pH down solution made in step 4 while simultaneously monitoring the shift in pH. The easiest way is to use a digital pH pen, place it in the container, and check the reading until you notice the levels drifting in the desired direction.
Step 6: Reach pH Target Reading of 5.7-6.2
The sweet spot you want to hit is around 5.5 – 6.5, so this means carefully adjusting the nutrient solution. If it is your first time and you are apprehensive about going overboard and adjusting back and forth, you can practice using water beforehand to get into the swing of things.
Adjusting pH When Using Only Water
One of my favorite feeding regimes is feeding a nutrient solution every 48 hours and only water in between. When it comes to the days of plain water only, all I have to do is follow steps 4,5 and 6 and simply water as normal.
Adjusting pH in Hydroponic Systems
When adjusting pH in the fast-paced world of hydro, I suggest you start by reading this article about the best hydro setups, especially covering everything pH-related.
Maintaining Proper pH to Get that Sweet Spot for Your Plants
The key to success is to ensure the water, nutrient solution, and growing medium are aligned in the pH department
Hydro – You are in total control of what goes into the reservoir, meaning that keeping the pH levels of your hydroponic system consistent is relatively easier than controlling a substrate. Check the reservoir using your pH pen daily and be prepared to make relevant adjustments.
Soil – Working with soil is much more forgiving than hydroponics as far as pH control is concerned, which is why soil-grown crops are always the perfect starting point for a beginner grower. The microbes and fungi in the soil will buffer any nutrients over a 72-hour period, maintaining optimal pH levels.
Coco – Coco coir is an excellent growing medium and my personal favorite. It is important to not only buffer your coco coir of any salts but also to keep the pH level at 5.8 – 6.5.
For the best plants, make sure you get the correct fertilizer and nutrients from the get go!
Cannabis Fertilizer
All the nutrients you need from seedling to harvest
Enough nutrients for at least 5 plants
Discounted combination deal
Suitable for soil, hydroponic and other growing mediums
Get Familiar with your H20 and Growing Medium pH
Failing to prepare is preparing to fail, so if you can take away one important key fact when it comes to pH management, that would be to get familiar with your water and growing medium pH. This requires regular pH checks for water, nutrient solutions, and runoff.
Testing Soil pH and Run-off Water pH to Avoid Nutrient Lockout
We have already established that the sweet spot for plants to access a full spectrum of nutrients is to drift between 6.0 – 7.0 for soil and 5.5 – 6.5 for hydroponics to avoid nutrient lockout and deficiency. Testing the run-off is one way to ensure you are hitting the target.
Soil pH meters work wonderfully well and provide instant data, allowing you to make real-time changes in the garden. You check the pH of your runoff by taking a small sample in a cup or from the saucer, then use your calibrated pH pen to check the reading. You will know from the test result if you need to increase the pH, lower it, or if it is fine.
Step 1: Water Plants Until Excess Drains
Step 2: Gather and Analyze Run-Off
Regular pH Testing Catches Imbalances Early
The early bird catches the worm, and if you can get in the habit of frequently checking your pH, you will certainly have an advantage at identifying and amending the pH of your grow.
If you notice the pH of your run-off water measuring less than pH 5.5, an an easy amendment is to add dolomite lime, calcium carbonate, oyster shell powder, or any other calcium-rich amendment and top dress your pots, this means adding some to the surface of your medium. If your pots are large then a slight tiling into the soil will help the soil pH become slightly more alkaline.
Step 3: Tend to your medium.
Step 4: Keep Tracking pH Levels.
Other Considerations
Safety first
Please keep your skin and eyes well protected and store your concentrated bottles of pH up or down out of direct sunlight and out of sight in a cupboard.
Calibrate properly
The maintenance and care of your pH measuring equipment should be a priority. Use KCL solution to avoid decalibrated measurements and wondering why you feel like a fool later down the line.
Soil growers beware
Even though soil growers will testify that they never need to pH anything, I must emphasize that knowing the exact pH at all times will empower you and also give you the upper hand in the event of a nutrient-deficient plant.
Conclusion
Adding a few drops of pH up or pH down to your nutrient solution may seem like an effortless task; however, it is an essential element to growing high-grade cannabis. Some lucky growers who never pH their nutrients may not experience any problems, but I must instill into any beginner growers the importance, value, and relevance of pH and its relationship to nutrient uptake, nutrient solubility, and plant health. Keep that pH well-balanced, and your plants will thank you with beautiful buds!
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