SUStee Soil Moisture Meter

The SUStee Soil Moisture Meter sits in the pot and reads the soil down where the roots are. A fabric core inside draws up water the way a root does. While the roots can still drink easily, the window shows blue. When the soil has dried to the point the roots have to work for it, the core dries too and the window turns white: time to water.

No batteries, nothing to calibrate. The core lasts about 6 to 9 months, then gets swapped for a fresh one. Three lengths: Small for pots 2.4 to 3.5 inches across, Medium for 4.1 to 7.1 inches, Large for 7.1 to 10.2 inches. Made in Japan.