PH is the measure of how “acidic” or “alkaline” something is, on a 1-14 scale. A pH of “7” is considered neutral, for example pure water has a pH of about 7. The measurements of pH has to do with the concentration of hydrogen in the sample. A cannabis grower can measure the pH of a water sample using special pH tester drops or a digital pH pen, like the one shown here on the right.
Okay, so why is pH important to cannabis growers?
Cannabis naturally likes a slightly acidic environment at the roots. Soil with a slightly acidic pH is what causes cannabis plants to thrive in the wild. Proper pH at the roots helps plants get access to the nutrients they need. If the pH at the roots is too high or low, the plant can’t properly absorb nutrients and you end up with cannabis nutrient deficiencies!
Paying Attention to pH Gives You Healthy Leaves!
Some growers get lucky and grow cannabis successfully without having to worry about pH. Perhaps they had just the right soil, and happened to have just the right water to create the perfect pH environment for the plant roots. If your plant is growing perfectly, without any signs of nutrient deficiencies, than managing the pH might not be something you’re concerned about.
Unfortunately, many growers aren’t so lucky and their setup naturally has a pH that is too high or too low for optimum cannabis growth. While there are ways of getting around testing pH for your cannabis grow, nearly all growers will do better by paying attention to pH.
What’s Are the Benefits of Managing pH?
By maintaining pH…
- plants are less likely to suffer leaf problems or nutrient deficiencies
- without nutrient problems, cannabis plants can grow faster and produce bigger yields
- occasionally growers are alerted to possible issues before they become a problem, for example if you determine the pH is too high or too low, you can fix it before your leaves start suffering from deficiencies
The main thing to remember is that maintaining the right pH at the cannabis roots helps the plant absorb nutrients. Why is that?
Nutrients take different forms (on a chemical level) depending on the pH around them. Some forms are easier for the roots to absorb than others. When the pH is too high or too low, the plant can show signs of a nutrient deficiency even when the nutrients are physically there at the roots.
With pH, you’re helping plants get access to all the nutrients all the time. While pH is important for all grows, it is most important for growers using cannabis nutrients. The way that liquid nutrients are formulated, they are highly available to plant roots, but only in the right pH range.
Nutrient-Related cannabis problems
Both overfeeding and underfeeding create stress for a plant that may cause it to develop symptoms like discoloured or malformed foliage and stunted growth. Some of the most common nutrient-related cannabis problems include:
Inexperienced growers often think that cannabis just needs three nutrients: nitrogen (N), phosphorus (P), and potassium (K). And while these macronutrients are indeed vital to healthy growth, cannabis plants need a complex mix of macro, secondary, and micronutrients to fuel both vegetative growth and flowering. When your plants don’t get the right amount of nutrients, they develop deficiencies that cause the death of old and young leaves, and leaf discolouration.
Nutrient deficiencies are typically caused by underfeeding, pH imbalance, and nutrient lockout. Left untreated, a nutrient deficiency can severely stunt a plant’s development and reduce both the quality and size of its yield.
The exact symptoms of nutrient deficiencies vary depending on what nutrient your plant is missing. Some common symptoms include:
- Dying old or young leaves
- Yellowing or brown leaves
- Red or purple stems
- Spotted or dry leaves
- Curled leaf tips and edges
- Warped leaves and stems
Some nutrient deficiencies can be remedied by simply upping the amount you feed your plants. In cases where it’s a result of pH imbalance and/or nutrient lockout, however, plants will require different treatment methods.
The opposite of a deficiency—nutrient burn—occurs when plants get more nutrients than they need. Overfeeding is an obvious cause of nutrient burn, but, here too, pH imbalances or nutrient lockout are also common causes. Characteristic signs of nutrient burn are dry, brown, and sometimes curled leaf tips and edges.
You must follow a strict feeding calendar and check your pH and EC levels before and after each feed to ensure your plants are not just getting their nutrients, but are also able to absorb them properly.
It’s worth noting that nutrient burn is typically only associated with the use of chemical fertilisers. Organic nutrients, which have a slow-release formula, typically don’t cause nutrient burn, as they take longer to be broken down and absorbed by your plants.
How does pH affect cannabis plants?
Now you know a little more about pH for cannabis you may be curious to know why/how the pH of your chosen grow medium has such a crucial role in the health, development and quality of your cannabis plant.
All cannabis growers will be aware that cannabis relies on nutrients and minerals to grow. That means a good, usable supply of the main N, P & K macro nutrients (Nitrogen, Phosphorus and Potassium) within the soil nutrients. Carbon (C) Hydrogen (H) and Oxygen (O) are macronutrients which are absorbed via air and water.
In addition to the main ‘macro’ nutrients, there are also vital micro nutrients which are required to maintain and support the complicated cannabis plant biochemistry. The micro nutrients include elements such as Magnesium, which is vital for photosynthesis, as well as Boron, Calcium, Iron, Manganese, Copper and others.
Micro nutrients, by definition, are only required in small quantities. But the presence of these micro nutrients is essential to the long term and short term plant health. Without them, you won’t be able to produce high quality cannabis. That’s why ph for weed is critical.
If the soil pH for cannabis is outside the preferred range the various biochemical pathways required for nutrient absorption and mineral assimilation simply don’t work. That means nutrient lockout. The nutrients may well be present in the soil, but the wrong pH for cannabis means that they can’t be absorbed and used.