Abstract: An indicator device is provided for insertion into the potting soil of a conventional house plant, for monitoring the moisture content thereof. The indicator includes a plastic housing encapsulating an elongated wick extending from a lower point where it is exposed beneath the soil level thereof to an upper point in an indicator chamber formed in the housing. The wick surrounds but does not touch a "signal element" comprising a layer of moisture-sensitive, color changeable substance (e.g., cobalt chloride), to carry moisture to the vicinity of the "signal element". The substance changes color in response to predetermined gains (or losses) in moisture content. Included in the housing structure are a plurality of vents adjacent the indicator chamber for precisely regulating the rate of evaporation therein, to control the response of the indicator to the moisture changes in the soil being monitored.