CONSTITUTION: A stem base warmer 10 comprises a latent heat storage body 12 and a heat insulation material 14, and keeps a stem base 102 warm. The latent heat storage body is formed by sealing the latent heat storage material in a container like a bag, and is installed around a stem base in a cylindrical manner. The heat insulation material is arranged outside the latent heat storage body. The thickness of the heat insulation material is set to the thickness or a thinner one which can at least pass the heat quantity for the latent heat storage body to reach the phase change temperature during the day. In the stem base warmer, during the day the air heat is stored in the latent heat storage body through the heat insulation material, and during the night the stored heat is released from the latent heat storage body and the released heat is prevented from escaping to the outside by the heat insulating material to keep the stem base warm.EFFECT: Since the air heat in a greenhouse is used to keep stem bases warm,
