This is a neat project for a planter that has an irrigation system powered by gravity.  There are detailed specifications that explain how to build the planter.

Basically the water in the red bucket moves down into the white plastic pipe which has tiny holes in it. It releases .05 gallons per hour which keeps the soil moist throughout the day.  There are drain holes in the bottom of the planter so that water doesn’t pool in the bottom of the planter box. There’s also an explanation of the physics behind the successful dripping of water at a rate slow enough to not flood the planter.  Ingenious design.

Click on the Passive Gravity Irrigated Planter link below to read the article and see the tutorial. There are “Next” and “Previous” buttons toward the bottom of each page that let you move through each page of the tutorial.

How to Make a Passive Gravity Irrigated Planter (Self-Watering Planter)