Measures the moisture content of soil to determine watering needs. Featuring a chart on the top that has three zones, the dry zone is for plants which require little water like cacti or other thick leaf plants, the green zone is for most plants that thrive in slightly humid to humid soil like begonias and azaleas, the blue zone is for soil that is very humid and watering should not occur at the rick of drowning plants, insert the probe into the soil and the needle on the dial settles on the appropriate zone.