Defining a flower border or edging for the gardens gives it a neat and formal appearance, prevents grass or weeds from growing in the contained area or mulch from washing out. Flower border ideas are many. For best success, always group plants with similar light, soil and watering needs next to each other. But if you looking for affordable flower border ideas, you can try this one; collect large rocks or stones to use as a garden border. Select rocks that can be set on or into the ground in such a way that they won’t shift. Search for suitable rocks in an accessible public natural area where you are legally allowed to remove them. All this idea costs you is your time and a bit of physical labor. Wash the rocks prior to placing them in your garden.