pH is a scale from 1 to 14 that measures acid-to-alkaline balance. One is the most acidic, 7 is neutral and 14 is most alkaline. Every full point change in pH signifies a 10-fold increase or decrease in acidity or alkalinity. For example, soil or water with a pH of 5 is 10 times more acid than water or soil with a pH of 6. Water with a pH of 5 is 100 times more acidic than water with a pH of 7. With a 10-fold difference between each point on the scale, accurate measurement and control is essential to a strong healthy garden. Cannabis grows best in soil with a pH from 6.5 – 7. Within this range, marijuana can properly absorb and process available nutrients most efficiently. If the pH is too low (acidic), acid salts bind nutrients chemically, and the roots are unable to absorb them. An alkaline soil with a high pH causes nutrients to become unavailable. Toxic salt build up that limits water intake by roots also becomes a problem. Hydroponic solutions perform best in a pH range a little lower than for soil. The ideal pH range for hydroponics is from 5.8 – 6.8. Some growers run the pH at lower levels and report no problems with nutrient uptake.