Sustee Aquameter (Green, Large) - Plant Soil Moisture Meter, Sensor, Probe, Indicator - Best for Potted Plants Senses water at root level, no dirty fingers & damaged roots trying to gauge moist soil by feel Leave the device in the pot to continuously monitor soil humidity and show you when to water Prevent withering & root rot, so your healthy houseplants can clean indoor air to keep you healthy! Award-winning product design - No batteries  Environmentally friendly  Creates little waste Sustee size L is best for pots over 7 inches in diameter - Each stick will last for approximately 6-9 months