How Does PH Affect My Cannabis Plants?

The Vault Cannabis Seed Store

For growers who are relatively new to cannabis, or even for those who have been growing for years, PH balancing can be a nightmare. In fact, getting the PH wrong can spell absolute disaster for a cannabis plant. To truly figure out the best PH for our plants, we need to start off by having a look at the basics.

What Do We Mean By PH?

As many of us likely learned in high school science PH refers to the balance of acid and alkali. In this case, we are talking about this balance in the soil we are using for our seeds. The scale runs from 0 to 14 with acid at the lower end and alkali at the upper. Plants will all have different requirements when it comes to the PH balance as they will sit in different places on the scale naturally. There are also different levels of acid and alkali in tap water, which along with the soil and the natural PH of the plant can be disastrous. To alter the PH in these natural and environmental factors, we may need to purchased soluble supplements. These can be found in most garden centres and can either raise or lower the PH of the soil, water, etc.

Cannabis PH

All plants have a different PH level, cannabis, in particular, has a PH of 6 – 6.5 so sits at the slightly acidic end of the scale. By keeping plants in this PH area we are allowing it to take in the nutrient it needs to thrive and stay healthy. If the PH is too high the plant roots will lose their ability to take in nutrients such as zinc, copper, manganese, and iron. Too low and they will lose out on calcium, magnesium and phosphoric acid. The plants need all of these nutrients in order to grow up big and strong.

What Will The Wrong PH Do?

If we leave our plants in the wrong PH environment a number of disastrous things can happen. The leaves can turn yellow, may begin to droop and might develop brown spots. The plants may also not be able to protect themselves from diseases or insects, potentially destroying the entire crop.

Unfortunately, these signs can also be symptoms of several other issues such as over or underfeeding, too little or too much light, the wrong temperature, the list goes on. If we don’t immediately recognise the signs for what they are we could attempt to correct an issue that doesn’t exist, thereby creating new problems for the plants.

How Do We Control the PH?

There are several different ways to alter the PH in a cannabis plant. First, if we have noticed any of the signs, it’s best to check the PH to ensure that’s the issue. There are many PH test kits available from garden centres or online.

Test Strips – These are the cheapest and easiest way to test the PH levels in the soil. However, a strip will only give a rough idea of the PH level and may not be specific enough for cannabis growing.

Dropper Kits – These kits are extremely simple and very popular since they are generally more specific than test strips. They are used to test the PH of the soil by placing it into a test tube and dropping in the testing liquid. Mix it in with the fertiliser then use the colour chart to check the PH level. Repeat the process with the runoff to get an accurate reading.

Electronic Probe – These are a little more expensive than the other options but are extremely accurate. Once the device has been calibrated it simply needs to be stuck into the soil and will give an accurate PH reading. For anyone who is repeatedly growing it is worth investing in an electronic probe.

Once the PH has been tested we may need to raise or lower the PH balance to keep our plants happy. This is a pretty simple process as PH Up and PH Down products are readily available from any plant shop or online. To use these products just mix them into the water being used to feed the plants. These products can be used alongside nutrient solutions to ensure a super healthy plant.

There are also natural ways to alter the PH of plants for anyone who doesn’t like using chemical products. To lower the PH, we can use items such as compost teas, worm castings, pine needles, wood shavings, manure or compost. To raise the PH we can try things like limestone, potassium, calcium or wood ash. By using natural products we can ensure our plants are healthy without messing around with chemicals or expensive growing products. It is important to ensure the mix of organic matter is the correct PH before applying it to the plant as the levels will be down to how it is used by the grower.

How Will PH Change The Plant Quality?

As we mentioned earlier a poor PH balance will stop the plants from absorbing the nutrients they need to grow. This could mean a smaller crop or less impressive buds or it could mean full-plant death. By carefully watching the PH of our plants we ensure they grow up big and strong. Strong, healthy plants will produce larger yields of denser buds that are covered in THC trichomes. They will also be far more capable of defending themselves against invaders such as pests, disease and mould. If we have double-checked the PH level and the plant is still showing signs of struggling then we may need to consider the other issues such as over/under feeding etc.

Essentially balancing the PH perfectly for our plants will give them the best chance in life and will make it easier to deal with other issues. If we focus on other potential problems and ignore the PH we may just be dooming our entire crop.

Remember: It is illegal to germinate cannabis seeds in many countries including the UK. It is our duty to inform you of this fact and to urge you to obey all of your local laws to the letter. The Vault only ever sells or sends out seeds for souvenir, collection or novelty purposes.

Make sure you never miss another Vault promo and sign up for our newsletter at

Latest posts