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pH For Cannabis Explained: Master The Scale

October 18, 2021

pH for cannabis is a puzzling subject for many novice canna farmers. You signed up for home growing, not to learn chemistry!

At-home cultivation teaches you many things, one of which is the pH level of the soil and water you’re using. This figure determines the rate of nutrient absorption. You want healthy, happy, well-fed crops, don’t you?

Worry not. Mastering this aspect of marijuana gardening isn’t that challenging, and we have your back. Today, we’re teaching you everything you need to know about pH levels for weed.

Water pH test
Water pH test

Why is the pH for cannabis important?

pH, or the power of hydrogen, is a measure of acidity or alkalinity of liquid solutions. Maintaining proper pH for cannabis with waterings and feedings is among the fundamental cultivation requirements. 

Cannabis isn’t a fussy plant, but it does have standards. Among those stands a narrow pH window at which it’s capable of absorbing nutrients necessary for its further development. Change in the levels of pH can even make some weed strains get different colors. Let’s examine the importance of pH for marijuana.

Note: Acidity plays one role, but it’s significant and has a snowball effect. In the same vein, these points string onto one another to make or break your next gardening project.

Preventing nutrient lockout

Nutrient lockout occurs when your plants can’t absorb the necessary elements from their environment. The side-effects resemble a nutrient deficiency and diminish overall plant health. 

There are two main culprits for this issue: 

  • Oversaturation with nute solutions, especially those high in salt.
  • Inappropriate marijuana pH levels.

The latter reason is much more frequent. Cannabis needs a specific pH range to use the feed you’re providing. Checking the acidity levels is always the first step towards resolving lockouts. 

Optimizing plant health

A cannabis plant can only thrive with enough micro, macro, and trace nutrients. When it spends too much time in acidic or alkaline soil or water, it becomes malnourished, which stunts growth and diminishes the lush greenery promised with the seed pack. 

For that reason, sustaining the proper pH for weed stands as a fundamental aspect of gardening success down the line. You can have the highest-quality lights and ventilation, but they make very little difference if the plant lacks the energy to develop.

Set yourself up for success by providing the ideal environment from the get-go. You’ll see much better results. 

No wasted money on fertilizers

Like with expensive equipment, you can purchase the highest-quality fertilizers on the market and still see your crops wither without the ideal cannabis pH levels

As a rule of thumb, always start with optimizing the base conditions

Only start introducing new elements when the basics are all as quality as possible. That way, your hard-earned money doesn’t go to waste on nutes that your crop won’t even touch.

Mixing nutrients for cannabis
Mixing nutrients

What are the benefits of maintaining the best pH for cannabis?

Maintaining the best pH for cannabis improves your gardening experience and the success of your project. Why is that so? Well, there are the short answer and the long answer.

In brief, the importance of proper hydrogen levels translates into the benefits of sustaining them. Let’s explore in a bit more depth.

Fewer nutrient issues

Nutrient deficiencies, burns, lockouts—how challenging it can get to keep your crops well-fed and thriving! Why add insult to injury by messing up the pH for cannabis?

Proper acidity levels let the plant take in everything you and the natural environment are providing. It gets enough NPK and other elements to go through vegging and flowering and come out covered in sticky colas on the other side. 

Of course, the chances of encountering a burn or deficiency are never 0%. It’s only that a pH issue is to blame for many of these plant health conditions. Avoiding that imbalance keeps you in a much safer zone

Higher growth rate

Cannabis needs massive amounts of nitrogen for vegetative growth. When it enters flowering, its requirements for phosphorus skyrocket. Without these elements in abundance, it fails to reach its full potential.

Optimal nutrition starts with cannabis pH. Think about it this way. 

Your child has to eat to grow, and they won’t eat if they’re not hungry. You can make the tastiest snack, but it makes little difference without appetite. Ideal pH is the hunger trigger for cannabis, driving it to take in the nutrients that make it thrive.

HMG organic nutrients
HMG organic nutrients

Higher yields

Stunted growth that results from nutrient lockout doesn’t only affect plant height. It also determines the size of your future harvest, sometimes as early as vegging. 

The best pH for weed pushes your crops to develop branches, bud sites, and sugar leaves. The yields become fatter, stickier, aromatic, and abundant. 

The ideal cannabis pH level for each medium

The pH measure of acidity and alkalinity is a 14-point scale. The middle point is neutral and includes liquids such as pure water. Everything below 7 is acidic, and above 7 is alkaline.

Cannabis doesn’t thrive in completely neutral mediums. Marijuana originates from wild regions, where the soil is slightly below the neutral point on the scale. Therefore, the ideal pH level for cannabis is somewhat acidic


The best pH for soil stands between 6.0 and 7.0 on the scale. Cannabis feels at home in such conditions, which lets it survive and thrive. 

Soil acidity depends on the type. In general:

  • Sandy soil and loam are slightly lower on the pH scale.
  • Clay is more alkaline.

Natural outdoor growers planting directly in their gardens get a bonus. The leaves, branches, and living things decaying in the dirt make it acidic, creating the ideal cannabis soil pH.

Soil pH
Soil pH


Hydroponic growing makes it much easier to manipulate the growing environment. You don’t have to worry about origins and chemical composition, only acidity.

When growing in water, the pH for cannabis should be a bit lower than with soil. A range between 5.5 and 6.5 is ideal

Other soilless mediums

Hydro isn’t the only soilless option that simplifies the cultivation process. Coco coir and peat moss also give you more control over the quality of your medium. 

Like with hydroponic, these options require more acidity. Maintain a 5.5 to 6.5 pH range.

How to measure cannabis pH 

You’ll know it’s time to check cannabis pH when your plants start displaying signs of nutrient deficiency. Prevention is better than cure, though, so why wait? Measuring the levels regularly and consistently is a good gardening practice that lets you nip any upcoming issue in the bud. Hello, healthy crops! 

How do you measure something you can’t see? You’ll find various paraphernalia options on the market to help you do just that. Here are the two most widely-used, most accessible ones

Using drops

A pH measurement kit with drops is an affordable, manual approach to checking cannabis pH levels. Color-changing drops or strips alter their appearance with different pH scores. You then compare the result to a color chart to determine where you stand.

Drops are mainly used for hydro growing, but the water you give your soil-based plants also influences pH levels. Here’s what you do:

  1. Pour a small water sample into the test tube. 
  2. Add several drops of the pH fluid. 
  3. Watch for the color change and compare the result to the chart. 

Discoloration indicates acidity or alkalinity. The results are usually approximate. It’s better to use these as preventative care, not while diagnosing an issue.

pH test
pH test

Using a digital pH meter

Digital pens are simple tools for measuring marijuana pH levels. 

They have a screen that reads the exact number upon usage, making them more accurate than the manual solution. Here’s how to use it:

  1. Dip the correct end into the water. 
  2. Read the result from the display.

The process is straightforward, but that ease comes with a heftier price tag. If you’re a regular, large-scale at-home grower, it’s more than a worthwhile investment.

pH meter
pH meter

How to adjust pH for marijuana

You’ve measured your hydro or soil pH for cannabis and faced a nasty surprise—the levels aren’t where they should be! 

Don’t worry, it’s not the end of the world. Fixing this issue is a simple affair, whether the number needs to go up or down. Here are some easy solutions for soil and hydro.

How to increase pH

If the medium got too acidic, it’s time to raise that baby back to optimal. The approach differs by medium type. In either case, you’ll be adding something alkaline to balance out the situation. 

  • Soil. Add organic matter such as bone meal or crushed oyster shells to raise cannabis soil pH. Dolomite lime and hardwood ash work better for severe acidity.
  • Hydro and watering. You’ll need a pH Up solution to pour into your medium, with either potassium hydroxide or potassium carbonate. As a rule of thumb, pour 2 to 4 ml per gallon of water and check the levels before adding more. 

Note: You can use the hydro option for soil-based cultivation. Add the solution into the water and flush with it.

How to decrease pH

If your medium went more to the neutral or even alkaline zone, it’s time to decrease it. Again, it’s a different affair with soil and hydro, but more acidity is the name of the game. 

Note: Once again, the hydro option also applies to watering soil-based crops. 

  • Soil. You have many organic options to lower the marijuana soil pH. Compost, cottonseed meal, and mold work like a charm for milder imbalances. Sawdust and wood chops are stronger solutions for more significant issues.
  • Hydro and watering. A pH Down product with phosphoric acid boosts acidity in hydro setups. This option is a bit more potent than pH Up, so keep it at 1 ml per gallon. Always measure again before adding extras.
Watering weed to control pH
Watering weed to control pH

Growing organic & pH levels for weed

Organic cannabis growing delivers higher-quality weed. It also makes the task of managing pH levels for cannabis much more straightforward

Organic cultivation eliminates chemical nutrients, which often cause salt buildup and nutrient lockout. Nonchemical products work on a different principle, supporting a healthy microbe in your growing medium. 

You use compost, worm castings, or bone meal to create a breeding ground for bacteria and fungi that make soil conducive to plant life. 

Note: Going organic eliminates some hassle of monitoring and adjusting cannabis pH. You should still check it if you notice a deficiency creeping up on your crops. 

pH for cannabis: Frequently asked questions

Let’s answer some frequent questions about pH for cannabis before sending you off to cater to your weed garden.

Do you measure pH water for seedlings?

Like cannabis in every other growth stage, seedlings need a specific cannabis pH range to develop correctly. You provide only light misting to seedlings, though. Otherwise, they might rot. Ensure that the soil or hydro setup is already in an optimal range (5.5 to 7) to secure health from the get-go.

What causes low soil pH?

Land use and management affect cannabis pH in the soil. Loss of organic matter through harvests and chemical fertilizers—primarily nitrogen and sulfur—increases acidity. Your garden soil usually needs amending after one successful harvest before you begin the next cultivation project.

What increases soil pH?

There are many ways to increase soil’s pH for cannabis, but limestone is the most prominent option. It replaces hydrogen ions, raising the levels and eliminating the issues of acidic soil. It also boosts calcium and magnesium levels. Oyster shells and bone meal also raise alkalinity, but only to a certain extent.

Does rain affect soil pH?

Precipitation can change the pH levels of the soil, but it’s far from the only factor in play. Rain leaches alkaline elements from the soil, causing it to become acidic with time. That’s why more tropical regions with heavy rainfall often have more acidic soil than dry regions. 

Final points about ph for weed

Learning about pH for cannabis ensures that your effort doesn’t go down the drain. It sets a steady foundation for gardening prosperity and makes each additional step ten times easier. 

Checking and amending pH levels doesn’t require much time and energy, but it makes a world of difference to your plants. Don’t skip this step. Now that you know the basics use your knowledge to boost your success rate and enjoy massive, healthy harvests.

Stay tuned to our blog for more handy guides such as this marijuana pH overview. Our educational resources are here to help growers of all experience levels make the most of each marijuana seed in their stash. 

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.

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