What is the best Water pH level for Marijuana

pH pen in runoff at 6.8

Hey there and welcome (back) to Free the Tree!

In this post we’re going to talk about the water pH when watering your Marijuana plant. If you’ve never done this before, you’re probably wondering what is the best pH level for Marijuana, but also why the h*ll the pH of the water has to do with anything… Hopefully you’ll get your answers here!

We tried to cover it all in the same spot, here’s what we’re going to cover in this article about pH:

Let’s get into it!

Why is pH important to Cannabis

So first things first, why would pH be important to a Marijuana plant?

In short, each living thing is actually influenced by the pH around them. The impact on plants results in their capacity to ingest the element it needs to grow. For example, Nitrogen can only be absorbed when the pH is over 5.4; If your pH is below that, you can put as much Nitrogen as you want in the water, it just enrich your soil (and possibly ruin it).

We’ll see this in the next section, but keep in mind that when you water your plant you want the water to be between 6 and 7, if possible right around 6.5. I say 6.5, but many growers stay lower or higher, but honestly if you’re starting out, just aim for the middle and it’ll be fine.

The most important thing is to stay between 6 and 7.

What is the best pH level for Marijuana

So this is where it gets tricky, depending on what time within its growth deferent levels are optimal. But again, if you stay between a pH of six and seven you’ll be alright. Generally it is said that the best pH for marijuana is of 6.5, a level at which all the nutrients can be absorbed

Below yo’ll find a table we set up within our guide on how to water your cannabis plants that is pretty useful to keep in mind. It shows you at what pH level each nutrient can be absorbed by the plant.

Here’s a recap of each element and the root pH needed

Minimum pH Maximum pH
Nitrogen (N) 5.5 7.5+
Phosphorus (P) 6.2 7.2
Potassium (K) 5.4 7.5+
Ca (Calcium) 6.5 7.5+
Magnesium (Mg) 5.8 7.2
Sulfur (S) 5.4 7.5+
Copper (Cu)
Iron (Fe)
Manganese (Mn)
Molybdenum (Mo) 5.8 7.5+
Zinc (Zn) – 5.0 7.1

As you can see, all the nutrients range between a 6 and 7, making that pH range the optimum root pH when growing Marijuana in soil.

Graph bringing forward the levels of pH per element

Chart representing each Nutrient and
what pH level it is needed
Image credit to growweedeasy

Reading up on pH levels? 

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Transplanting Cannabis

How to measure the pH level in your watering mix

Globally there are 3 ways you can measure your pH level, either by using a pH pen, pH testing liquid and pH strips. They all measure the acidity and alkalinity based on a 0 to 14 scale, 7 being neutral (water).
Since the pH meter is an electronic device the measurements are more precise, you get the acidity levels at a decimal level (0,1). If you use the strips you will just get a general idea of the pH level, since you’re basing yourself on the color of the testing solution.

Using a pH pen

Here’s how and when to measure the pH of your water:

  1. Add the Nutrients within the water
  2. Stir the water, don’t shake the bottle! Take something to stir the water. Air will bring the pH up, giving you the wrong level.
  3. Take your pH meter or pH tester and place it in the water. Try to get it at least 2.5 inches (5,5cm) into the water.
  4. Keep it in the water for a the very least a minute. You will see the digits changing and stabilising, once this is the case look at the number. In the case it’s over 6.9, get some pH down in there, on the other hand get some pH up (or water) in there!If your pH meter is giving you a number that you just can’t believe, place it into a pH solution (I recommend one set at a pH of 7) and check if the pH meter isn’t off. If it is you have to tweak the little screw at the bottom until it shows you the right number
  5. Once you have the wanted pH, you can shake up the recipient in order to get that water oxygenated, your roots will love it, and get to watering your plants!

And there you go! In just a couple steps you’ve made sure that when you water your plants they can actually take in the nutrients they need, she’ll thank you with a nice growth

pH pen in water at 7

pH pen in water at 7

How to measure the pH in your soil

So I got to this issue because my pH meter was giving me some crazy numbers, supposably my water was over 8.0… after adding nutrients, yeah right! So I winged it until I could get to the grow shop.

Once I had some pH buffer, I rescaled my pH meter (generally a little screw at the bottom of it) and it was good to go, but wait… at what pH should my water be at?

If I had been giving it waterings with a pH that was too high, then I should be giving her a low level pH, and vice versa if my mix was too high up.
After reading on who knows how many growing blogs here’s the trick I found:

  1. Make your mix at a pH of 6.5. Two benefits, the first is that whether it was too high or too low, she’ll be able to get the ingredients needed, the second is our following step.
  2. As we’ve seen in our watering tutorial (here), you should get about 20% runoff.
    Measure the pH levels of that runoff
  3. If the runoff is under 6.5 then you’ve been watering too low and your next watering should be of a higher pH level (6.6-6.8)
    On the other hand, you’ve been watering too high so you’ll have to give her lower pH’s next time (6.2-6.4)
  4. After that get back to your previous levels.
pH pen in water at 7

Measuring the pH of the watering solution
Photo credit : Our Instagram

First watering runoff in tray and glass

Collecting the water (aka runoff)
Photo credit
: Our Instagram

pH level at 6.8 on first watering

Measuring the run-off
Photo credit: Our Instagram

How to adjust the pH level of your water

So, now that you know what pH level you need to have, you must be wondering how to adjust it right?

This is pretty straight forward, you’re going to want to get something more acidic or basic, depending on your situation. Most tap waters are around a pH of 7, so once you’ve added your nutrients the water level should be close to good, only a drop or 2 of pH down mix will do the trick.

In the market there are 2 types of products that will enable you to adjust the pH levels:

pH down

Most frequently used and generally around a pH level of 4, this will help you bring the pH levels down.
I’ve found that, in a 2L water bottle, a drop of this brings down the pH of about 0.1, so the math is pretty easy on that one. If you’ve got a pH of 7.2, than add about 6 drops, stir without oxygenating the water and test again.

pH Up

In order to raise your pH the easiest way is to add water to it, as long as you don’t need to go over 7.0 🙂

Organic nutrients

Now we’ll do a whole article on organic nutrients for your Marijuana plant, but keep in mind that they do exist but you have to be careful!
You may think that using lemon juice or white vinegar or even baking soda to bring your pH down  would work, and it actually will.

But this can be counter productive, the lemon juice may attract bacteria and the 2 others are composed of salts which and block the root system of your plant which in the long run will kill it.
Here’s a good blog thread on rollitup on the subject, but my advice here would be to just get pH up or down in your local grow shop, its not expensive and you know the components in it aren’t harmful to your plant.

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pH Tips for Marijuana Indoor Culture

In this section we’re going to group together all the tips that we’re learning along the way so it’ll grow with more and more ideas and tips for your watering sessions

Oxygenated water

Your babies roots will love you for it, but oxygen raises pH levels so shake your container after measuring the pH level!
Although it is important for you to stir the mix before taking the measurement since the nutrients will alter the level in your water.

How much pH Down to add?

We’ve noticed that in about 2L of water, 1 drop of pH Down 4 get the overall pH down of about 0.1.
So if you’ve measured your mix at 7.2, about 6/7 drops and you should be good (still do mix and measure!)

What to use for pH UP?

For this you need a alkaline solution or…. a neutral one right? Sooo water! All you need to do is add more water, or else empty some of your mix out and get some fresh water in, and there you go!

Community Questions on pH Levels for Cannabis

If you haven’t found your answer don’t hesitate to send us a message via the contact bar or with our tool on the bottom right of your screen. We’ll come add it in this section as soon as we find the answer 😉

The questions we’ve received so far:

If the pH of the Run Off water is of 7.1 is it OK for Cannabis?

Here we can’t fully answer since we don’t know the pH value of the water used. What we can say is that with a run off of pH of 7.1 either your water or your soil has a pH that is too high.  
Over a short period this might not be an issue, since at a pH of 7.1 most nutrients are still available, but you should definitely gradually lower the pH of your water during the next watering(s).

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