The invention concerns indicating devices for use with plants for indicating whether or not a plant is being subjected to the correct conditions of temperature and/or moisture. A label or tag (12) carrying instructions (13) concerning the type of plant for which it is suitable is printed with an enclosed volume of liquid crystal ink (14) which has one colour (7) at a suitable temperature for the plant and other colours (8, 9) when the temperature is too hot or too cold. The device also carries a strip (16) of material which changes colour according to the moisture level of the soil in which it is inserted to give an indication when the soil is too dry. Alternatively an electronic circuit and probe may measure the moisture level. A further device (17) may measure the light level. <IMAGE>
