Busy gardeners love the Plant Sitter Sensor System. The plant sitter sensors can be used with a water source to water or fertilize your plants through drip irrigation as your plants need it based on the soil’s dryness. The system delivers water or fertilizer to your plants at a slow and consistent rate. You simply place the plant sitter sensor into your plants soil, the siphon tube into a water source, and walk away. Each ceramic sensor cone measures 4-1/4 inch x 1-1/2 inch and includes an 18-1/2 inch siphon tube.