Disclosed are a device and a method for utilizing the thermal energy in the soil to protect against damage to plants, such as citrus trees, from cold weather and to promote the growth of plants. The device comprises a heat pipe having an evaporator section which extends into the soil in the vicinity of the root system of the plants and extracts heat from the soil. The heat is then transferred to a condenser section which extends above ground and radiates and convects the heat to the plant. This also refrigerates the root system of the plant to extend the dormancy period. Also disclosed is a method for providing a supply of water to a plant, comprising the use of a heat pipe to create a temperature gradient around the root system of the plant, whereby water from the surrounding soil is caused to flow toward the plant.
