Container plantings often need to be watered much more frequently than in-ground plants—sometimes even twice a day. To reduce your time spent watering and to give plants more of a fighting chance try self-watering containers.
A self-watering container is a pot with a reservoir of water in its bottom. As the soil becomes dry, it draws water from the reservoir. All you do is keep the reservoir filled with water, and the plants take care of themselves.
Two popular self-watering containers are EarthBox and Lechuza.
There are many sizes and shapes and other brands available.
And here is one way to make your own.