Abstract: An alarm system for an indoor Christmas tree comprises a temperature sensor located on the tree or in proximity to the tree, an excessive-temperature detection circuit connected to the sensor and producing an excessive-temperature output signal when the sensed temperature exceeds a predetermined limit, and an alarm receiving the excessive-temperature output signal and producing an alarm indicating that the predetermined temperature limit has been exceeded. The excessive-temperature detection circuit and the alarm are located remotely from the tree, are powered by a standard power distribution system of the building in which the tree is located, and are connected to the temperature sensor at the tree by wires. An alarm may also be produced in response to an open circuit or a short circuit in the wires connecting the excessive-temperature detection circuit to the temperature sensor.