The Balancing Act: Managing Cannabis Soil pH

The Balancing Act: Managing Cannabis Soil pH

What is pH?

Most understood as a measure of how acidic or alkaline your soil is, pH is incredibly important to cannabis growers when considering the health of their plants. pH is a common term in a chemistry lab, short for ‘potential Hydrogen’, which tells you the hydrogen ion concentration in a particular substance.

This scale ranges from 0-14, with 7 denoting neutral pH substances. Substances with a pH below 7 are acidic, while substances above 7 are alkaline or ‘basic’. pH can be influenced by many factors in your crop’s environment, including soil composition, water quality, organic matter content, and fertility inputs.

Why does pH matter for cannabis?


Hydrogen ion concentration can affect nutrient availability, as well as directly impact microbial activity in your soil. Ensuring that your growing environment is at the right pH means that nutrients are readily available. pH influences the rate of cation exchange, as well as supports a flourishing microbial population that promotes nutrient absorption, stress resilience, and plant vigor. Nutrients are most readily available when your environment is slightly acidic, making the ideal pH range for cannabis between 6.2-7.

How to find out my pH?

There are two common methods for identifying pH in any given system: pH test strips and a pH meter. Test strips are cheap, easy to use, and readily available, you can find them at almost any hardware store. A pH meter is less readily available, slightly more expensive, and needs to be carefully calibrated or you can get an inaccurate reading. However, they are easy to use and provide a more exact pH value than a color scale.  

Measuring your soil’s pH will be the most effective for identifying your cannabis’s general living situation. However, your water and fertilizer pH may impact your growing system, so it is important to be mindful of your inputs.

If growing in an in-ground garden bed, or in multiple pots that may be receiving different inputs, test multiple soil samples from different areas of your growing space. Testing multiple samples will give you the most accurate readout of your garden. This includes soil taken from different depths of your garden beds. If testing a growing mix, make sure your media is thoroughly homogenized, or the accuracy may be impacted.

Identifying pH Imbalances

Because nutrient deficiencies are a primary issue when your plants are grown outside of their ideal range, it can be tricky to diagnose a pH imbalance as the cause of nutrient deficiency. In extreme situations, your plant can enter a state of ‘nutrient lockout’ where your growing conditions become so averse that your plants can’t consume any of the nutrients they need. Managing soil pH can help you avoid lockout, even if your plant is experiencing stress. Extreme pH values can also lead to nutrient toxicity, where certain nutrients are too bioavailable compared to others.

When your pH is too low you may see:

  • Interveinal Leaf Chlorosis (Where the leaf turns yellow, but the veins remain green)
  • Brown or purple spots on leaves
  • Leaf die-off or tip burn
  • Withered, twisted, or stunted growth on leaves
  • Dark green leaves with red, orange, or purple tinges

These symptoms are caused by low availability of Phosphorus, Calcium, and Magnesium. You can see why growers would easily confuse pH imbalances with issues of nutrient content! You may also see signs of iron toxicity in low-pH environments.

When your pH is too high you may see:

  • Interveinal Leaf Chlorosis (Where the leaf turns yellow, but the veins remain green)
  • Brown spots on leaves
  • Tip death on new leaves, and spots of leaf necrosis
  • Withered, twisted, or stunted growth on leaves
  • Dark green leaves with red, orange, or purple tinges

These symptoms are caused by low availability of Phosphorus, Calcium, Iron, and Copper. Low pH and high pH nutrient lockout have similar side effects due to Phosphorus and Calcium having limited ranges of bioavailability. At pH levels of above 7.5, many of your beneficial microbes are no longer able to perform work. Bioavailability is difficult to recover until your pH returns to a normal range. Because the symptoms of low pH and high pH are so similar, a soil test is an incredibly useful tool to identify next steps, and get your soil back on track.

Fixing pH Imbalances

If your plants seem to be struggling with a pH imbalance, your first step is to test your water, soil, and fertility inputs separately to narrow down the source.

Water and fertility inputs can easily be corrected. You can use an alternate water source, filter water, or install a pH corrector for water inputs. For fertility inputs, you may need to adjust your application rate or apply liquid nutrients as a foliar application versus a soil drench.

Soil takes a little more work to get back in the optimal range. Your soil type will determine a lot about the pH of your soil. Sandy soils, for example, don’t contain a lot of pH buffers due to low clay and organic matter content, making them more acidic.  Clay soils, on the other hand, are often more alkaline due to a low infiltration capacity. In either of these cases, additional organic matter can improve soil structure and balance pH by adding buffer points for pH, as well as reviving microbial populations.

Activated Compost contains rich organic matter and a nutrient complex carefully tailored to feed soil microbes. When plants expend energy to adjust the pH inside of their cells, their growth can become stunted and suffer over time. Microbes in the soil can perform the work of pH regulation, allowing your plants to focus more energy on growing healthy flowers and dense buds. BIOACTIVE LiquiLife provides diverse microbes to further support pH regulation, as well as promote nutrient uptake in pH environments outside of the ideal range.

pH is a tricky thing to manage on your soil, but organic matter and microbes can help you achieve the perfect balance for your cannabis crop.

For more information about getting your soil to a healthy pH, and for questions on a healthier cannabis plant, don’t hesitate to reach out to our team of expert growers!