The invention relates to a moisture sensor 16 for an irrigation apparatus 10, 100, 118, 121, 130, 140. The moisture sensor 16 being operable to monitor a moisture content for a medium in which it is located to provide a control signal for operating the irrigation apparatus 10, 100, 118, 121, 130, 140 for controlling a water supply 26 to the medium. The moisture sensor 16 comprises a sensing capacitor 46.