What is pH and Why Does it Matter?
If you remember back to high school science class, pH stands for "potential for hydrogen" because it is a measure of the hydrogen ion concentration of a solution. In practical terms, pH is a scale from 1 to 14 that reflects the fluid's relative acidity or alkalinity, with 1 as highly acidic, 14 as very alkaline, and 7 as neutral. Understanding and checking pH is critical to indoor growers because it affects the ability of plants to absorb nutrients.
For most popular indoor crops, including edible, ornamental and medicinal plants, the pH of the nutrient solution needs to be slightly acidic 6.0 to 6.5 for all of essential elements to be taken up by the plants.
Outside of the ideal range, nutrients may become “unavailable” to plants, even if sufficient quantities are present. Simple pH monitors are relatively inexpensive and easy to use. You should use one to check every batch of nutrient solution you mix up.