Systems and methods to supply water to plants in a direct and efficient manner by employing aboveground plumbing to individual plants, but not allowing the water to be dispersed aboveground. The water is directed to an underground container or cartridge assembly that dispenses the water through a dissipater (e.g., wick) into the surrounding soil. The cartridge assembly of the underground irrigation system may be installed in-line with supply water lines and deep enough that the dispersed water does not return near the surface which allows for working the soil over the underground irrigation system. Each of the cartridge assemblies of the underground irrigation system may be installed in line between two plants in a narrow trench at a depth of approximately 6 to 12 inches (e.g., 8 inches), so that each end of each cartridge assembly supplies water to one side of one of the two plants.
