The invention is apparatus which can be fitted in a container, therein modifying the container to function as a self-watering planter. The apparatus includes a partitioning element that includes an extruded element having a hollow tubular section that terminates in a center opening and a wide flange. The extruded element separates the container into an upper portion (potting soil and plant), a lower portion (liquid reservoir), and a common portion (potting soil, water, and ultimately some root). The flange is a solid plate with a lateral opening that enables liquid to be conveyed past the plate. Roots cannot grow through it. The lower portion has an overflow outlet through the containers sidewall. A fill pipe extends from the rim down to the reservoir, so substantially no liquid is added directly to the upper portion. A film having a slot for the plant covers the container.
