Vegetables, especially tomatos are hungry for waters all the time. To grow them in containers, you perhaps need to wather them twice daily on a sunny day. On the other hand, a consistent watering (dripping) system may take away nutrients in soil. One solution to this problem is to add a water reservior at the bottom of the container. There are many kinds of light weight plastic plant containers with double walls on the market. Do not follow manufacturer's instruction to drill holes at the bottom all the way through. You can easily make self-watering containers from them. The following picture shows a self-watering container that I made for growing tumbler tomato: Step 1. Drill six 3/8" or 1/2" holes evenly in the inner wall. Do not drill through the outer wall. Step 2. Drill some 1/2" holes at the bottom in the outer wall. Do not drill through into the inner wall (this is very important!) Some containers already have pre-drilled holes with plugs. If so, just pull plugs off. Step 3. Cut a piece of metal mesh (you can get the mesh from home improvement stores. They are used for the construction of exterier stucco walls). Cut it in square and bend the four corners upward in order to fit into the round container at the level shown in the picture. Step 4. Optionally, cut a small hole at the center of the mesh and insert a 3/4" or 1" PVC tube all the way to the bottom of the conatianer. The other end of the tube should be highier than the top soil surface. You can monitor and measure the water level from the top of the tube by a stick. Step 5. Fill soil and plant. Do not use fine grained or sandy soil. I use 50% compost. Cover mulch on top. I use cedar chips.