pH, what does it really mean?

Simply stated, pH is a measure of the number of hydrogen (H+) ions in a solution, whether that be soil, hydroponics, nutrients, or any other solution. The pH scale ranges from 0 (100% Hydrogen ions) to 14 (100% Hydroxide ions, OH-) with pure water being at 7, since it is an equal mixture of hydrogen ions with hydroxide ions (H+)+(OH-)= H20.

Going further, why is the sweet spot where it is for certain plants?

Well, it largely has to do with nutrient availability at those pH levels. For example, at pH 6, Nitrogen, potassium, and most of the necessary micronutrients are very available. However, at that same pH value, you begin to see a decline in phosphorus, calcium, magnesium and molybdenum availability. With the cannabis plant’s “sweet spot” being in the low to high 6 range, this suggests that phosphorus is not quite as important in the growth and development of this plant as are the micronutrients that are

more readily available in this pH range, such as Iron, manganese, copper and zinc, with Nitrogen and potassium obviously being the most important nutrients in the growth and development of these plants. This optimum pH range also comes from the evolution of the cannabis plant. For the most part, cannabis evolved to live in tropical areas in well-aged clay soils with high organic matter content, which all means that these soils were low in pH and high in microbial activity.

Let’s take another plant that is notorious for its fickleness with pH, the blueberry. Blueberries grow best in very low pH soils, with an optimum range between 4.5-5.5. Blueberries evolved in forested ecosystems, where the soil pH is low, with lots of microbial activity. Blueberries also require more iron than many other plants, so it is no wonder that a low pH is so important when growing blueberries. This is just another example of how the optimum pH for growth is really just a reflection of nutrient requirements.

So, the short answer when discussing optimum growing pH for different plants: it’s complicated. There are many different factors that are influenced by soil pH, including microbial activity and the presence of certain species of bacteria and fungi that form symbiotic relationships with plants. But studying the optimum pH of your plants can reveal some interesting things about their nutrient uptake and requirements.

The biggest thing to keep in mind when adjusting pH is that it is in a range and it will fluctuate, remember, soils are alive, and your plants also excrete acids and other things called exudates from their roots in order to transport nutrients out of the soil solution and to the root hairs, which will also change the pH of the soil. If your pH does need adjusted, do it slowly, as quick changes in pH will stress the plants, and not allow them to adjust to the new environment in which their roots are growing (think of jumping out of a hot tub and into the snow). It is much easier on your plants to deal with a temporary deficiency than it is for them to deal with a huge change all at once. So just make sure to give the soil pH a little bit of time to change after adding acid forming fertilizers or a pH adjuster before making another treatment.

Please leave us questions below, and give us questions to answer in future blogs. Until next time, remember,

Don’t Just Feed Your Plants, FUEL THEM!