minimum water level in chamber 22 the indicators 64 a 64 b may take the form of a raised or colored line alternatively or additionally container 10 may include an electronic sensor and display 66 to measure and indicate the water level in chamber 22 container 10 is used in the following manner plug 56 is removed from first aperture 52 water is introduced through first aperture 52 and into chamber 22 until the water level 68 reaches the maximum water level indicator 64 a water will flow into bore 62 of tube 60 during filling of chamber 22 water level in cavity 42 will increase slightly during filling of chamber 22 once sufficient water has been added to container 10 plug 56 is reinserted into first aperture 52 to seal access to chamber 22 water level 68 in chamber 22 is at a distance u201c h h 1 u201d fig4 from bottom wall 16 of outer shell 12 a quantity of water 24 from chamber 22 flows through apertures 50 in inner shell 14 and accumulates in cavity 42 to a height of h 2 from the bottom wall 16 a lesser quantity of water flows from cavity 42 through opening 45 in flower pot 44 and into.