pH When Growing Cannabis

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Learning about pH when growing cannabis can seem a little complicated at first. Before starting you need to know what pH is and how it works. Then you need to know what pH cannabis plants prefer at different stages of their life cycle. And to make it even more complicated you need to know what pH cannabis plants prefer in soil, or hydro! 

Not only that, but you also need to learn how to check the pH of water and feed, and how to adjust it if it isn’t in range. It can all seem like a lot, but I assure you, it is very simple. 

Throughout this guide we are going to go through everything you need to know about pH when growing cannabis. At the end of it you will realise it is all much simpler than you initially thought and you will have no problem adjusting and fixing pH in the future. 

So let’s begin with what pH is and why it matters. If you have any questions at all, please feel free to ask in the cannabis growers forum

Does pH Matter When Growing Cannabis?

pH is the measurement of how acidic or alkaline something is. When growing plants, it will usually mean how acidic or alkaline the growing medium is, or how acidic or alkaline the nutrient solution is when you water your plants. 

The pH scale ranges from 1, which is the most acidic, to 14, which is most alkaline. Water is usually at a “neutral” level, which is pH7, right in the middle of the scale. 

the ph scale for cannabis plants

Cannabis plants like to be in a grow medium that is slightly acidic. The preferred level will differ depending on what medium your plants are growing in. If the pH of your grow medium, or nutrient solution is not in the correct range, your plant will not be able to eat properly! This will cause problems. 

To keep your plants happy and healthy, keep them growing at the right pH level for the medium they are growing in. . 

pH For Growing Cannabis in Hydro

The pH for growing cannabis in hydro will be between 5.8 and 6.2. This is the best pH level for plants grown in hydroponic mediums like DWC, NFT, Rockwool, Clay Pellets, Hydroton and more. Any medium that is seen as a “Soilless Medium” should be pH’d to 5.8 – 6.2.

What is the Best pH for Cannabis in Coco?

Coco coir is considered a soilless medium, therefore it is hydroponics. All hydroponics mediums should be kept between the pH of 5.8 and 6.2. 5.8 is the optimal level, but for best results let the pH “swing” a little to 6.2. 

Hydroponic pH Level Chart

Click on this hydroponic pH chart to download it to your device absolutely free! Don’t forget to sign up to our cannabis growers forum too. 

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Do You Need to Adjust pH When Growing in Soil?

The best pH for growing cannabis in soil is between 6.5-7.0. Because 7.0 is often the pH of water, adjusting the soil may not be necessary. Also, some soils will be treated with dolomite lime. This will help the pH stay at the right levels if it is given water that is slightly outside of the preferred pH range. 

Therefore, check the pH of your water before watering your plants to ensure it is at the right level. If not, you should adjust it before watering the plants. 

pH Nutrient Chart Soil

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How to Adjust pH when Growing Cannabis

Adjusting pH for cannabis plants is easy! All you have to do is add some “pH Up” or “pH Down” to the water or nutrient solution before feeding it to your plants. These chemicals are very powerful and should be used carefully. Just adding a couple of drops to water can be enough to change the pH levels. 

Begin by using a pH meter and placing the tip into your water or nutrient solution. Wait for at least ten seconds and check the display on your pH meter, it will show you a reading. 

If the number displayed on your pH meter isn’t within the correct range, you need to adjust it. Add pH up or down to the water, stir well and test again. Continue this process until the pH is within the correct range. 

ph up
ph down

When the pH of the water or nutrient solution is right, you can give it to your plants. If you’re growing cannabis in soil, coco, rock wool, or any solid medium, pour the water through the medium to change the pH of the medium. If you are growing in water (hydro mediums) simply top up the reservoir.

Best pH Tester for Growing Cannabis

The best pH tester for growing cannabis is an electrical “pH pen”. There are a couple of brands that stand out as the best for growing cannabis. They are Essentials, and Blue Lab. Anything less than these will give you inaccurate readings and will be unreliable. For best results buy an Essentials pH Meter, or a Blue Lab pH meter. 

You can read more about pH testers for growing cannabis here:

You may be tempted to buy cheap pH pens. This is not a good idea. You need to have peace of mind and make sure your plants are growing in the right pH. Only a decent pH pen can give you that peace of mind. If the pH is off, your plants will suffer. 

What pH Should a Cannabis Seedling Be?

The best pH for a cannabis seedling is dependent on whatever medium your plants are growing in. If growing in coco or other hydroponic mediums, keep the pH around 5.8. On the other hand, if you’re growing cannabis in soil, keep the pH around 6.5.

If you need any help, please ask in our cannabis growing forum. 

pH, Veg vs Flower

Throughout a cannabis plant’s life cycle, the nutrients it needs will change. Some growers will choose to alter the pH depending on what stage of growth the plant is at. For example, cannabis plants growing in the vegetative state are usually kept in slightly more acidic mediums than plants going through the flowering stage. 

This isn’t majorly important though, and it is always best to keep things simple. Your plants will grow great with the correct pH of 5.8 for hydro, or 6.5 for soil, you do not need to make it more complicated and adjust them. ~It is just that some growers like to. 

Best pH for Vegetative Stage

Throughout the vegetative stage of a cannabis plant’s life cycle, you should keep the pH slightly acidic. For cannabis plants growing in soilless mediums and hydro, keep the pH around 5.8. If you are growing cannabis in soil, keep the pH of the soil around 6.5 during the vegetative stage. 

What Should pH Be During Flower?

As a cannabis plant moves into the flowering stage, its need for nutrients changes. To accommodate for this some growers will reduce the acidity of the pH slightly, making it more alkaline. This will allow the plants easy access to nutrients it needs. 

During the flowering stage, keep cannabis plants growing in coco at around 6.2 pH. For plants growing in soil, bring the pH up to 6.8. Those levels should work fine. 

Get Help with Your Grow Today!

Thanks for reading this article about pH, I hope it has helped you understand things a little more. If you have any questions or you need help with your grow then please start a thread in the forum to ask our cannabis growers community. We are always happy to help.

Good luck with your grow!

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