Items required for the project
The gardening system has three parts: the control system, the humidity sensor that measures the humidity content of the soil, and a separate irrigation mechanism that irrigates the plants as required. We will use low-power components for our system (other than the irrigation pump) so that we can run them 24/7 without worrying about energy costs and they will also give us the flexibility of powering our system with batteries.
Waterproof junction box
You probably have a garden outdoors. You might want to keep your outdoor electronics near your garden as well; it will help to have a junction box that protects your electronics from rain and similar acts of nature. You can use hot-melt glue or quick-setting silicone paste to fix the electronics to the junction box as well as for providing some waterproofing:

Arduino Pro Mini 5v ATMEGA328P
We decide to go with the Arduino Pro Mini as our control board as we have decided to make our gardening system fully self contained...