You are hereHow to pH Cannabis - Best pH for Soil or Hydro

How to pH Cannabis - Best pH for Soil or Hydro


by Nebula Haze


Table of Contents

Introduction: Why is pH Important?

What's the Best pH?

How to Test and Adjust pH for Cannabis

Common Questions About pH

Summary: 8 Things You Must Remember About pH


 

Intro: Why pH? Why Should Cannabis Growers Care?

PH is the measure of how “acidic” or “alkaline” (basic) something is. Measurements of pH has to do with the concentration of hydrogen in the soil. So why is pH important to cannabis growers?

Cannabis naturally likes a slightly acidic environment at the roots. Soil with a slightly acidic pH is what cannabis plants thrive on in the wild. Proper pH helps plants get access to the nutrients they need.

Proper pH Prevents Nutrient Deficiencies!

Achieve healthy cannabis leaves by maintaining pH

Some growers get lucky and grow cannabis successfully without having to worry about pH. Perhaps they had just the right soil, and happened to have just the right water to create the perfect pH environment for the plant roots. Many growers aren’t so lucky, and there are ways of getting around testing pH for your cannabis grow, but nearly all growers will do better by paying attention to pH.

What’s Are the Benefits of Maintaining pH?

By maintaining pH...

  • cannabis plants can grow faster and produce bigger yields

  • plants are less likely to suffer leaf problems or nutrient deficiencies

  • nutrients become more available to plant roots, so your plants get what they need for each stage of life

  • fix the pH your water if it happens to be too high or low, or compensate for nutrients that change your water pH

  • occasionally growers are alerted to issues before they become a problem

Maintaining the right pH at the cannabis roots helps the plant absorb nutrients.

Nutrient sources take different forms (on a chemical level) depending on the pH around them. Some forms are easier for the roots to absorb than others. When the pH is too high or too low, the plant may start showing signs of a nutrient deficiency even when the nutrients are physically there at the roots.

By maintaining the right pH at the roots, you’re helping plants get access to all the nutrients all the time. While pH is important for all grows, it becomes most important for growers using liquid cannabis nutrients.

Take Me Straight to the Cannabis Root pH Charts!

As a result of the pH being too high or too low, cannabis plants may start showing signs of nutrient deficiencies even if the nutrients are available in the growing medium.

Growing in Soil? You may not need to worry about pH

In fact, growers who rely on using properly amended and/or composted soil are the least likely to be hit by nutrient deficiencies caused by pH problems. The more organic matter in the soil, generally the less the soil pH matters as far as nutrient absorption The natural process of soil breaking down helps make nutrients more available to the roots. But cannabis needs very specific nutrient requirements to get the best results.

If you want to grow cannabis without worrying about pH, you’ll likely want to grow using amended, composted soil. Read about composting your own soil for growing cannabis. However when it comes to composting soil, it generally takes a bit of time, space and mixing before your soil is ready to use.

Mixing Super Soil with Jinxproof and Mr. Spliff - two famous organic marijuana growers and teachers
 

No Time to Mix Soil? Liquid Nutrients are Easy, Cheap & Effective

A lot of growers don’t have the time or space to mix up their own soil, which may involve composting, understanding how micro-organisms in the soil affect nutrient absorption, maintaining a compost pile, etc. Because growing in soil can involve a lot of prep work (or for those who live in a city where there’s not enough room for an organic, composted soil grow), there are hundreds of liquid nutrients which can be much more convenient for cannabis gardeners.

Liquid nutrients can be used to provide plants with everything they need at all stages of life. By following a simple nutrient schedule, growers are able to use the perfect amount of nutrients at the right time to power the growth of the plant, leaves and buds.

Whether you’re growing in soil or hydroponics, you can use cannabis nutrients to make sure your plants have all nutrients needed, without having to mix up any soil yourself. Just follow the basic instructions for the nutrients, and your cannabis will thrive.

For many growers, liquid nutrients make growing cannabis more simple, straightforward and satisfying.

Learn About Liquid Nutrients for Cannabis:
http://www.growweedeasy.com/cannabis-nutrients

 

Learn more about cannabis nutrients here!
 

Who Should pH? Everyone Who Uses Liquid Nutrients

Paying attention to pH is pretty much required for any cannabis growers using liquid nutrients. Even soil growers using liquid nutrients should pay attention, though soil growers tend to get more of a buffer from all the organic matter, especially those starting with great composted soil that has been made for a plant like cannabis.

Unless you're willing to learn about soil for cannabis and mix up your own soil, there's probably no way you can get out of pH management - if you refuse to manage pH, your only option is to just try it your way to see what happens.

Some growers get lucky winging it, and if you’ve successfully grown a plant like tomatoes or corn, you’ll probably be able to provide for your plants using what you already know.

But if you’re just thinking about buying standard potting soil from the local garden store, or using soil you found around your house, you’re probably going to need liquid nutrients to supplement your cannabis grow for the best results and yields. Maintaining pH is one of the best tools you have to get the most from your nutrients.

This colorful nug is here partly because the grower chose to check and adjust pH

 

Once you get the hang of maintaining the pH, it's a breeze and will take you only seconds. And after you have your grow dialed in, you may not even need to check pH as often because you know what to expect.

 


 

What's the Best pH for Cannabis?

 


 

It's a good idea to let the pH cover a range instead of always adjusting to the exact same pH number. Some nutrients are better absorbed at slightly higher pH readings, while others are absorbed better at lower pH readings.

If your marijuana plant roots are experiencing the wrong pH, the most important thing is to react as soon as you noticed, and not wait until you actually notice problems with the leaves. It can be tempting to ignore a pH problem, but you’ll get the best results by acting before there’s a problem.

In the wild, cannabis prefers an acidic environment.

Soil ~ 6.0 - 7.0 pH

For soil an optimum root zone pH is between 6.0 and 7.0, with the most time spent with a pH between 6.2 - 7.0.

Growing marijuana in soil pH Chart

In a soil environment that doesn’t use liquid nutrients, pH isn’t as important. When using liquid nutrients in soil, you will almost always need to manage pH to get the best harvest.

 

Hydroponics or Soilless ~ 5.5 - 6.5 pH

For hydroponics (and soilless setups like coco coir) an optimum root zone pH is between 5.5 and 6.5.

Some soilless growing mediums with a lot of organic matter may need a slightly higher pH to thrive. For example if you heavily amended your growing medium with worm castings, you will want to aim for a pH between soil and hydroponic ranges.

For a hydroponics setup with roots in water, this pH chart will be able to guide you so you never get nutrient deficiencies from the pH being off.

Growing marijuana in hydroponics pH Chart (including soilless mixes that include coco coir, vermiculite, perlite etc)

With hydroponics, it's especially important to allow the pH to range slightly, as you can see above, some nutrients can only be absorbed at higher or lower pH's.

In a hydroponic setup, you will always be using liquid nutrients, so save yourself a ton of trouble by watching and adjusting the pH as needed! The pH will naturally change over time, and you only need to correct it when it starts going out of the 5.5-6.5 range.

No Need to Be Exact - Let pH Range Up & Down

The thing to remember with pH is that you don't need to be exact. What you do need is to be consistent in keeping the pH from creeping too high or too low in your plant root zone.

As long as you stick within the recommended pH ranges above, you will prevent the majority of all nutrient problems caused by too-high or too-low pH.

Tips

  • Be consistent in making sure pH stays in the range

  • You don’t need to be exact, just keep an eye on things

  • Add all of your nutrients to your water first before checking and adjusting the pH. Your nutrients will affect the pH of your water so it's important they get added before making any adjustments.

 


 

How to Test and Adjust pH for Cannabis

 


 

What Supplies Do I Need to Test & Adjust pH?

‣ pH Tester

‣ A Way to Adjust pH

There are other methods of adjusting pH, but using pH Up and pH Down are the only method I've personally used -  I know they work great for growing cannabis. 

Note: Some soil growers will add a handful of dolomite lime as their mixing their soil. Dolomite lime can help buffer pH and keep it from getting too low, while also adding a source of calcium and magnesium. This method is not recommended unless you're mixing up your own soil.

‣ A Container to Mix Water

  • I prefer a 1-gallon container that has been used for drinking water, but you can use a bigger or smaller container depending on your needs. I generally prefer mixing in containers that have been made for drinking water. Most importantly avoid anything fragile, especially glass (which can break your instruments or shatter) 

‣ Water

‣ Nutrients (If You’re Using Nutrients)

 

How to Adjust pH For Your Cannabis Plants

 

  1. Add Nutrients to Your Water - always do this first because nutrients can change the pH of your water

  2. Gently Shake or Stir

  3. Test pH with pH Tester

  4. Adjust pH if Needed by adding pH Up or pH Down solution (use as little as you can). How much pH Up and Down do I use?

  5. Re-test to make sure pH is in proper range

  6. Water plants with pH'ed nutrient solution or add to hydroponic reservoir

  7. Check - Soil or soilless growers check the pH or their runoff water - try to use the earliest runoff if possible. Hydroponic growers check the pH of their water reservoir by taking a small sample about an hour later.

That’s it!

I like to mix up my nutrients in a 1-gallon water container. Generally I try to mix nutrients with water in a drinking-safe container. I fill the container with water, add nutrients if needed, adjust the pH and then I shake it vigorously before watering plants. I can then test the pH of the runoff water to alert me to any possible problems.

For Sirius, a hydroponic grower with a 5-gallon tank, he fills a 5-gallon drinking container with water, adds nutrients, adjust pH if needed, then adds the water to his plant’s nutrient reservoir. He then checks the pH of the reservoir about an hour later.

I’ve also heard of people who use buckets or even trash cans for mixing a lot of water. Just avoid using glass to mix up your nutrients (it can break, it can break your equipment, and it can make it difficult to test pH).

Tips for Cannabis Nutrient & pH Management:

  • Don’t Go Overboard: With liquid nutrients, it’s usually better to give too little than too much. You can always add more, but it’s harder to take nutrients back

  • Never Mix Nutrients With Each other: Always add nutrients directly to your water. It’s bad to mix nutrients together. They can react with each other in a way that can make nutrients less available to your plants, and you might not be able to see anything. Most nutrient bottles or pH adjusters will come with a clear warning that says the same thing. Always add any additives directly to the water - your plants will thank you for it.

  • Avoid Using Both pH Up and Down At the Same Time: Avoid changing pH too much if possible. Some growers will add pH Up or Down, overshoot their goal, then try to fix it with changing the pH the other way. Not only does it become harder and harder to get the right pH this way, adding too much pH Up & Down is not helpful to your plant roots.

  • Tap Water is Easier to pH Than RO Water: Tap water or mineral water has an extra buffer of extra minerals and other “stuff” in the water. This helps prevent the pH from swinging up too high or too low quickly and can make pHing easier. RO water has very little buffer (it’s mostly just pure water) and tends to swing up and down in pH easily with just a little pH Up or Down.

  • Sources of Nitrogen Tend to Bring pH Down: Nitrogen is one of the major nutrients needed for the cannabis vegetative stage, and because of this vegetative cannabis nutrients tend to bring the pH down. In the flowering stage, the lack of high levels of nitrogen in bloom nutrients means your nutrients won’t make as big a difference to the pH of the water.

  • Don’t Shake Water Too Much Until After You’ve Checked pH: When checking and adjusting pH, some growers like to shake their water container to make sure everything is evenly mixed. This works well, and roots love the extra oxygen, but it’s important to understand that after shaking the nutrient water for a long time, the additional dissolved oxygen will raise the pH of the water. Don’t worry about this - don’t retest then readjust the pH. If you’re going to hand-water to your plant, you want to make sure you go by the pH of the water before it was shaken up. If water is allowed to sit for a while, it’s normal for the pH to change a bit. When it comes to mixing, make sure you mix water gently so nutrients and pH Up or Down are evenly distributed, but avoid vigorous shaking until after you’ve already adjusted the pH.

  • Soil or Soilless Growers Should Regularly Check Runoff Water pH: If growing in soil or a soilless growing medium, it can be helpful to test the pH or the runoff water - if it’s very different from what you put in at the top, you may have fertilizer or nutrient salt buildup in the growing medium which is affecting the pH at the roots. It’s a good idea to test the runoff water regularly, especially when plant is having nutrient problems, to alert you to possible pH problems so you can fix them before your plants are affected.

  • Hydroponics Growers Should Regularly Check Reservoir pH: To adjust the pH of a reservoir, never add nutrients, pH Up, or pH Down directly to reservoir! If you can’t change out the whole reservoir, or just need to make small adjustments, this is what you need to do: Take some water out of the reservoir, adjust the pH/Nutrients in the separate container, then add it back to the reservoir. If growing in a hydroponic system, it’s a good idea to check the pH of the water reservoir about an hour later, since that’s what your plant roots will be exposed to. If the pH has moved a little, don’t worry as long as it’s in the right range for hydroponics (5.5-6.5)

  • pH Drift is Normal. Try to stay in the suggested range and you’ll usually be fine.

 


 

How Much pH Up or Down Do I Use?

 


Summary of Steps

  1. Get Current Root pH

  2. Adjust pH if Needed - Instructions

  3. Test Again


 

1.) First get a ballpark figure of the current root pH

Hydroponics

  • Test the pH of the reservoir by taking a small sample of water and use it to test the pH.

Soil or Soilless Mediums

  • Next time you water the growing medium, test the pH of the water going in

  • Test the pH of the water that runs out of the bottom (runoff water)

pH of nutrient water should be about equal to the pH of runoff water

Note: Assume the runoff pH is about halfway between the water going in and the root pH. PH uses a logarithmic scale, but when close to a pH of 7, this idea should work well enough for growing purposes. There is not an easy scientific way to measure pH of soil or a soilless medium, but the following method will help new growers get a handle on how to adjust pH before they get a feel for it.

This ballpark method assumes the runoff pH is about halfway between the water going in and the root pH. This is only an approximate measurement!

Think about the pH of the water going in. It’s the perfect pH. If the pH that comes out the bottom is higher or lower than what you expect, that means you need to do the opposite as far as pH.

You put in the pH water you want...

  • If runoff pH is lower than expected, you want to make pH go up.

  • If runoff pH is higher than expected, you want to make pH go down.

 

2.) If pH at Root Zone is Off,  Adjust the pH

Hydroponics

Avoid changing pH too quickly. It’s better to change pH slowly to the right place than to overshoot and go way too high or low.

  • If pH is too high, take out a fifth of the water from your reservoir and add a small amount of pH Down solution (a little bit goes a long way). Return to reservoir and check pH again in an hour.

  • If pH is too low, take out a fifth of the water from your reservoir and add a small amount of pH Up solution. Return to reservoir and check pH again in an hour.

  • pH tends to go up with oxygenation (bubbles, dissolved oxygen) - this is normal

  • Vegetative nutrients tend to cause the pH to go down (especially nutrients with high levels of nitrogen)

  • There's no easy way to know the exact amount of pH Up or Down, but use as little as you can until you get a feel for how it will affect your water.

 

Soil or Soilless Mediums

  • After you've determined the ballbark figure for the current root pH, you know whether your pH is too high or low.

  • Mix up plain water (no nutrients) with a small amount of pH Up or pH Down. This plain pH'ed water should be at a lower or higher pH to help move your pH to the range you’re looking for. Using plain water will help leach out extra stuff affecting the pH.

  • Unfortunately there’s no exact formula to adjusting pH, because factors such as growing medium, nutrients, drainage and growing setup have a huge effect on pH. There's also no completely accurate way to measure the current pH, making things even less exact. Unless you're growing in hydroponics, there's no exact way to maintain pH, you're just going for as close as you can.

  • You will need to use trial and error to figure out what amount of pH Up or Down works for you in your setup with your nutrients. Remember that pH changes depending on the nutrients you’re using! Vegetative stage nutrients tend to bring pH down compared to flowering nutrients (but not always).

  • If you’re new to adjusting pH, start small with pH Up and Down, and only work your way up to bigger amounts after you’ve gained some experience. Most growers will be able to figure out their personal measurements within a few waterings.

  • Avoid ever using pH Up and pH Down in the same container

  • Test runoff pH consistently during your first grow using liquid nutrients. Make sure you're testing pH at least once every watering or two.

  • There's no easy way to know the exact amount of pH Up or Down, but use as little as you can until you get a feel for how it will affect your water.

Tips For Soil & Soilless Growers

  • pH problems are sometimes caused by over-fertilizing (giving too many liquid nutrients or supplements). If you believe this is the case, flush the growing medium.

  • Flushing means giving your plants 1-3 times the volume of it’s container with plain, pHed water. This helps wash out extra nutrients. After the flush, water plants with a light nutrient solution. It’s normal for plants to droop when they’re overwatered (such as after a flush), but the drooping will go away as soon as the medium begins to dry out. After the top inch of growing medium has dried out, water the plant as normal and test the runoff water to see if the pH has corrected itself.

  • Many new growers provide too high levels of vegetative nutrients. These nutrients contain a lot of nitrogen, and this can cause the pH of the growing medium to go down. Using time-released nutrients (such as Miracle-Gro original soil) can add nitrogen to the soil when you don’t want.

 

3.) Test pH again soon! Learn if you need any more adjustments.

If you’ve recently adjusted the pH of your growing medium or hydroponic setup, or made any other major changes, it’s important to keep testing pH regularly for a while until you know how the changes are affecting the pH.

 

 

 

How to Use pH Control Kits

A pH Control Kit works by using drops that reveal the pH of your water. Basically you take a small sample of water in an included test tube, add a few drops of the pH solution, and then match the resulting color to figure out the pH. 

Many pH Control Kits come with pH Up & pH Down included. Even though they're often sold by "General Hydroponics," these kits work great for soil in addition to hydroponic applications.

Directions

Find the pH

  1. Take small water sample in included test tube

  2. Add a few drops of pH fluid

  3. Match the color to find the pH (compare to chart)

Adjust the pH

  1. Add a small amount of pH Up if pH is too low

  2. Add a small amount of pH Down if pH is too high

  3. Re-test

 


 

Which Digital pH Testers Work For Growing Cannabis?

 

With all digital pH testers, it's important to get...

  • Calibration fluid <-- Most important

  • Storage Solution

  • Cleaning Solution

If you don't get these extra items, you won't be able to take proper care of your digital pH tester and it won't give you accurate pH readings and they won't last nearly as long.

All testers come with step-by-step directions that tell you exactly what you need to do to make sure you pH tester is accurate for years to come!

 


HI 98127 - A digital pH tester by Hanna InstrumentsHanna Instruments HI 99104 pH Tester - this one doesn't get rave reviews, but it's been reliable and accurate for me for years and many grows.

About the HI99104 pH Tester Model:

  • You'll need a coin the calibrate this tester

  • You'll need to get calibration solution (like every pH tester)

  • Follow the directions, including use and storage - it's pretty straightforward


The HI98128 digital pH tester by Hanna is top-of-the-lineHanna Instruments HI 98128 pH Tester - this high-end tester has all the bells and whistles you could possibly want from a digital pH Tester, but may be overkill for new growers.

About the HI98128 pH Tester Model:

  • You'll need to get calibration solution (like every pH tester)

  • Follow the directions, including use and storage - it's pretty straightforward


 

Don't get a "TDS" or "PPM" meter by accident!

There are many other digital pH testers besides the ones listed above, and many of them will work great. Just be sure you don't actually buy a "TDS" or "PPM" meter by accident, which is different and does not actually test pH. If you want a TDS meter, that's great, but many growers accidentally buy one and don't realize what it's actually for. Learn more about TDS & PPM

 


 

Common Questions About pH

 


 

Do I need to pH the water before or after adding nutrients?

Add nutrients first, then pH the water.

You should test the pH after you add nutrients to the water (if adding nutrients). The nutrients will often change the pH of the water, and you’re concerned with making sure the pH of the water is right, as experienced by the roots.

If not using any nutrients for this feeding, simply adjust the pH of the plain water.

 

How Easy is it to Use Liquid Nutrients and Maintain pH?

Liquid nutrients for plants are simple to use (usually consisting of 1-3 bottles for all stages of life) and don’t take up much space. These nutrient systems can be used to provide exactly the right nutrients for your cannabis plant at each stage of life.

Learn about nutrients & get customized nutrient schedules for growing cannabis

Many growers use liquid nutrients made for soil to supplement their soil grow. There are also nutrients which are made to be used in hydroponic setups to provide all the nutrients the plant needs throughout its life, even without soil.

Whether made for soil or hydroponics, all liquid nutrients are used in a similar way.

The Hydroponics vs Soil debate continues to rage on, but no matter what your choice, the nutrients available today have exactly what’s needed by a cannabis plant to thrive at all stages of life, coasting perfectly to harvest time.

For soil growers, being aware of pH is important, especially those using liquid nutrients. For soilless and hydroponic growers, liquid nutrients and pH management are required tools that give growers a greater ability to affect plant growth - for better or worse.
 

Is it Hard to Maintain pH?

No way, maintaining pH for your cannabis grow can be easy and intuitive!

Learn all about how to check and adjust your pH for cannabis

Measuring and adjusting the pH is as simple a process as mixing up the nutrients themselves. The pHing process can take less than a minute, and the results you’ll get in better growth and bigger colas are worth the few minutes it takes to pH.

Basically you take a small sample of your water and test to find out the pH.

You can use a pH Control kit or a digital pH tester. The pH control kit has you add a few drops of a special solution to your small water sample and match the resulting color to find the pH. A digital pH tester can be stuck directly in the water to get the pH printed on a small screen, but requires regular calibration and proper storage with storage solution to stay accurate.

Whether you’re using a pH control kit or a digital tester, basically you use your water sample to learn the pH. You have “pH Up” or “pH Down” solution to adjust if it's too high or too low.

 

How to bring pH up or down outdoors

Great for outdoors, these options for adjusting pH are not recommended for indoor growers unless you know what you’re doing :)

Note: There are other methods of natural pH management besides the ones that follow, but these are the ones we know will definitely work. They are intended for growers who are growing on larger patches of land and need to change the pH of a lot of soil.

Bring Up pH

Lime is one of the most proven ways to bring up the pH of soil outdoors.

  • Use agricultural or garden lime in soil to bring up pH (the smaller the particles of lime, the sooner they will become available). This type of lime (agricultural or garden lime) adds pleny of Calcium, too, but not a lot of Magnesium.

  • Dolomite lime will add plenty of Magnesium in addition to Calcium. Many cannabis growers like to add handful of dolomite to their soil when mixing it up to buffer the pH and provide a steady source of calcium and magnesium.

Mix lime thoroughly with the soil, and keep it relatively moist to “activate” the lime. The finer the limestone source, the quicker it will be absorbed - powdered lime works much more quickly than larger sources of lime, which take time to break down.

Liming to bring up pH and enrich with Calcium/Magnesium should be used at the beginning of the grow before plants are placed in the soil. Cannabis likes slightly acidic soil, so it's important not to go overboard and bring the pH too high (soil for cannabis should be pH 6.0-7.0, so pH 7.0 and above is too high).

Don't use lime unless you follow the directions closely, you don't want to cause a bigger problem than the one you're trying to fix. 

Adding lime in the middle of a grow can cause or mask a bigger problem with the nutrients and salt buildups in the soil. You’ll get the best results if you add the lime to moist soil 2-3 months before growing, so the lime has time to break down in the soil and adjust the soil pH.

However, some cannabis growers do add lime to their flowering cannabis plants grown in soil to help buffer the pH and keep the pH from dropping. When adding lime in the middle of a grow (after you've established that there's too-low ph in the soil) do not add more than 1 teaspoon (5 ml) per gallon of soil.

Bring Down pH

There are a few common way to bring down the pH of soil:

  • Aluminum sulfate - works more quickly

  • Elemental sulfur - tends to take longer

Alkaline soil needs to have the pH lowered to grow cannabis. Cannabis needs a soil pH of 6.0-7.0, and alkaline soil has a pH above 7.

Just like lime, using aluminum sulfate or elemental sulfur to bring down pH can be tough to get just right. Don't use lime unless you follow the directions closely, you don't want to cause a bigger problem than the one you're trying to fix.

While aluminum sulfate is effective at lowering the pH in a relatively short amount of time, elemental sulfur should only be used at the beginning of the grow. You’ll get the best results if you add the elemental sulfur to moist soil 2-3 months before growing, so the sulfur has time to break down in the soil and adjust the pH. Depending on where you live, Sulfur (or “Sulphur”) is also known as "soil sulfur," "powdered sulfur" or "flowers of sulfur."

 

How Do I Learn More About My Local Water?

Check with your water company to learn more about your tap water. They will be able to provide you with lots of important info.

You can also do some testing on your own such as...

Special Water Won’t Help Your Grow Unless You Need It!

Many growers don’t need special water. Some growers think that special water will somehow give them better results when it comes to cannabis growth and harvest. The truth is, special water is not going to help your grow unless you actually need it.

 

What options do you have if your water is not good for growing cannabis?

  1. RO (Reverse Osmosis Water) - RO gives you nearly pure H2O. Everything has been taken out of the water, including minerals. With RO, you have a blank slate to start with, so you have 100% control over the water in your grow. However, with RO water, there’s less buffer to help prevent pH fluctuations. PH tends to swing up and down more easily in RO water. RO also tends to be associated with calcium and magnesium deficiencies (since these minerals are normally found in water), so adding a Cal-Mag supplement is usually beneficial for RO growers.

  2. Filtered or Store-bought drinking water (treat similarly to tap water)

  3. Rain water (treat similarly to tap water - some rain water isn't good)

 


 

Summary: What You Need to Remember About pH & Growing Cannabis

 

  1. Get a pH Tester - there’s digital pens or a pH Control Kit.

  2. Get pH Up & pH Down - great for quickly adjusting the pH of potted or hydroponic cannabis plants

  3. If you are using liquid nutrients with your cannabis plants, pH is essential to getting the best growth and yields

  4. Know how to maintain pH, especially growers using liquid nutrients.

  5. If you are not using liquid nutrients (for example a grow with amended and/or composted soil, possibly worm teas, etc), you may not need to adjust pH, but it’s still a good idea to test pH of runoff water if possible so you’ll have warning if there’s a problem

  6. Flush plants if you believe pH problems may be caused by providing too high levels of nutrients or supplements

  7. Let pH drift up & down as long as it stays in the right range - Soil pH should be between 6.0 - 7.0. Hydroponics pH should be between 5.5 - 6.5

  8. Add all nutrients and supplements before testing/adjusting pH. Many nutrients/supplements can change the pH of your water. Make sure to add everything to your water before you attempt to test or adjust the pH.

 


 

Jump to...

The Basics of Growing

Which Nutrients Should I Use?

7 Steps to Fix 99% of Growing Problems

Train Your Plants for Bigger Yields

 


 

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