Fertile Earth WSOD-1 WaterStik Plant Moisture Sensor, Outdoor By using the WaterStik InstaRead button the user can simply push the button and know immediately the status of the plant The only device that identifies whether the plant has been over watered The WaterStik-Outdoor can be used to measure multiple areas in a landscape or it can be left in a single zone to monitor a specific area or plant. Color of light indicates if the plant needs water or not Blue means overwatered, green means good, yellow means water soon, and red means water now.