The Luster Leaf Digital PLUS Soil pH Meter measures the acidity/alkalinity of garden and container soil. But that's not all! This monitor has the pH preferences and requirements for more than 150 of the most popular house plants built in. No more referring to separate books for this information - simply select the plant being tested by name and then insert the probe into the soil. The meter will tell you the ideal range for that plant and tell you what the pH level is in your pot - its that easy!