Sub-irrigated planters (SIP) are simple devices that allow low-maintenance, low-water consumption container gardening.
A simple SIP has three major parts: a container for soil, a container for water and a wick that allows water to be drawn from the water container into the soil container.
This diagram shows the major parts of a simple SIP made from a plastic pop bottle.
For instructions on making SIPs from plastic pop bottles, visit:
http://suresimple.blogspot.com/2009/04/recycling-juice-and-pop-bottles-as-sips.html