Elizabeth Waddington from treehugger said that Even if you do not have the use of any outside space, there are still some clever ways to make the most of whatever inside space is available to you. On a sunny windowsill, you can grow a lot more than you might think possible. So let’s scale things down here and talk about how you can maximize yield and grow successfully even when a windowsill is all you have.
First of all, try thinking vertically. Remember, you are not limited to the small space on the windowsill itself. You could also build up from this surface. Stacking small containers one on top of the other, with the largest at the base, and the smallest at the top is one simple way to increase growing area. (You can see some ideas here.) You can also create planting towers – which will allow you to grow plenty of lettuce, herbs, and other leafy crops.