Abstract: Multi functional sensors are described. A silicon based sensor utilizes metal layers arranged as resistors around a central pair if resistors separated by a humidity sensitive polymer with one of the central resistors being a heater. This enables temperature humidity wind speed and direction to be measured. In another embodiment an array of resistors is printed onto a flexible substrate to form the basis of an array of sensors. A soil moisture sensor, which is also useful as a leaf wetness sensor, incorporates a novel self calibrating capacitive sensor structure. The flexible substrate is rolled into a stake that can be inserted in the soil so that below ground sensors measure soil moisture and above ground sensors measure temperature, light, humidity, wind speed and direction.