Create areas with stones

You can also create specific areas of stones, not to put plants inside. They can give you a more clean and simple to balance maybe if on the other end you have many plants. You can mix it with cement, however, are the stones that give a much more natural.
 
In this case uses stones of different colors or types. Find different options on the market.
 
 
The stones can help narrow down the areas that will have your garden.