The Importance of Using pH and PPM Pens for Your Cannabis Grow Room


Whether you’re new to growing and embarking on your first indoor crop or you’re a cannabis-cultivating veteran who has been doing this for decades, you need to be focusing on pH and PPM. It doesn’t matter if you’re growing 2 plants or 200, problems with pH can cause irreversible damage to a cannabis grow room.

There are a lot of details and considerations for controlling pH and PPM for growing weed, and it might take a while to get the hang of. To help you get there, the best thing you can do is to invest in a pH/PPM meter, which takes the guesswork out of everything.


Why pH is Important for Growing Cannabis

The Importance of Using pH and PPM Pens for Your Cannabis Grow Room

The pH scales measure how acidic or alkaline a solution is. The scale ranges from 1 to 14, 1 being very acidic, 14 being very alkaline (also known as basic), and 7 being neutral. If you’re wondering what growing weed has to do with this, all you need to know is that cannabis plants perform best at a very specific range on this scale.

The specific pH that your plants crave depends mostly on the medium you’re using to grow. Whether you’re using organic soil or growing hydroponically without soil makes a big difference. For soil growing, measurements between 6 and 7 are usually pretty good, but lower pH is recommended for soilless growing (between 5.5 and 6.5).

So now the question is, why is pH important?

Aside from the general fact that your plants perform best within a specific pH range, we haven’t really gone into the details of why they thrive within that range. It all has to do with nutrient uptake.

Plants need nutrients like nitrogen, potassium, and phosphorous to survive, and it’s your job as the grower to deliver these nutrients. But no matter how much N-P-K you give them, it won’t matter if the pH for your garden is too high or low.

A study from the University of Vermont states that “soil pH is important because it influences several soil factors affecting plant growth, such as (1) soil bacteria, (2) nutrient leaching, (3) nutrient availability, (4) toxic elements, and (5) soil structure… Plant nutrients leach out of soils with a pH below 5.0 much more rapidly than from soils with values between 5.0 and 7.5.”

All that scientific jargon basically means that plants aren’t able to uptake and hold onto the nutrients they need when pH is below 5.0 or above 7.5. That same study later goes on to say that “plant nutrients are generally most available to plants in the pH range 5.5 to 6.5.”

What happens if the pH fluctuates throughout the grow op?

To control your pH, the main thing you’ll be doing is altering the pH of the water you give to your plants. You’ll add in solutions called pH-Up and pH-Down and then use a meter to measure the levels to get them right where you want them.

These solutions are extremely helpful, but it doesn’t mean you’ll be able to get the exact same pH every time you water. But that’s completely OK, and it’s actually recommended. As long as you stay within that ideal range (between 6 and 7 for soil growing, 5.5 to 6.5 for hydro) it’s totally fine for the pH levels to fluctuate a few decimal points each time you water.
matter if the pH for your garden is too high or low. 

The Importance of Using pH and PPM Pens for Your Cannabis Grow Room

What Is PPM? Why Is It Important?

The Importance of Using pH and PPM Pens for Your Cannabis Grow Room

PPM, short for parts per million, is another unit of measurement, only this one measures the amount of total dissolved solids – TDS for short – in a solution. Basically it has to do with how much “stuff” is in the water you’re feeding your plants.

Many new growers don’t even think about PPM or TDS, but for advanced grow ops, it’s important to know what’s in the water you’re using. Water doesn’t just quench the crop’s thirst, but it also carries the nutrients you’ll be feeding to the plants.


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Calculating PPM is a great way to know exactly how much of each nutrient you’re giving them. Measuring pH is definitely more important, but taking into account TDS and PPM is a great way to take your crop to the next level.

What’s the Easiest Way to Measure pH and PPM?

In the olden days, growers used pH measuring strips that changed colors based on the acidity and alkalinity of the solution. These pH testing strips are still available, but it’s recommended that you use modern technology to make things easier and more accurate.

There are lots of pH pens and PPM meters available to growers, and some of the best of them include both pH and PPM measuring in one easy-to-use device. BlueLab is the most popular brand, mainly thanks to their combo meter that measure pH and PPM as well as TDS (total dissolved solids), electrical conductivity, and temperature.



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