Professional interior landscapers often use various sub-irrigation systems so that they can minimize the number of maintenance visits required at their client accounts. They are used in decorative planters and are very effective for all sized plants. However, they are not cost effective for home plant owners.
Water wicks are the simplest and least expensive extended-irrigation option. They can be used with any sized plant pot and don't require repotting or retrofitting. Besides the wick, all that is needed is a reservoir (a container that holds water) and a waterproof platform for the nursery pot to sit on above the water level in the reservoir. You can use any sized reservoir, including a large bucket of water as long as the grow pot can sit above the water in the reservoir. Multiple plants can have their wicks inserted in the same reservoir.
For smaller plants, a thick styrofoam block cut to size can be placed in the reservoir container for the plant pot to sit on. The blocs can be doubled up to increase the height. Styrofoam is waterproof and completely un-natural so it never decomposes. I have also seen bricks used as platforms.
I have sometimes used plastic window boxes as a reservoir for multiple smaller (6-inch) plants that are set on top of styrofoam in the bottom of the window box. Anything that holds water has potential as a water reservoir.
Once you understand the concept of wick watering, which is pretty basic, you can use an unlimited variety of sealed containers to hold the water and use the wicks with any number or size plants.
