Designing a rain garden is an exercise in engineering: you are taking the rainfall off the house and directing it into a temporary holding bin, so that it can slowly seep into your soil. If you want, it can travel into a cistern for use at a later time. But the water doesn’t leave your property. You need to figure out which parts of the house to convert and the size of the holding bin.
The first decision is where your rain garden will be placed and how much rainfall can drain into it. This step will tell you how large the garden will be: it can always be larger, but never smaller or you will be creating additional runoff. Consider our Design your Landscape class to determine placement, plants, runoff and supporting landscape. Design your Landscape
The second step is to take a soil sample or a percolation test: you want to see how well water moves – or doesn’t move – through your soil. Generally, in this area, we need to replace the soil with another medium that will both filter the rainfall and allow it to move into the groundwater. You also must provide for overflow, should you have too much rainfall for the size/shape of your garden.
Now you must determine when the area gets sun or shade and how much: what time of day and how many hours.
And now you should know where the rain garden will be placed, how much water it will handle, the plants you prefer and the overall design of the garden.
Rain garden design looks at how much rainfall we can capture from the building and where it needs to go. The hard part is digging. The easy – and fun – part is choosing what to see and then planting. If it works, great! If it doesn’t work as well as it should, you need to revisit what is wrong and re-design.
Plants are typical for a NC landscape and can be found in just about any garden or nursery center. They can be natives or cultivars and you should know what type of site situation each one prefers. Checking rain garden plant lists, you will find where they should be placed within the garden.
A few plant choices for long blooming display:
Help is available
I hold a certification in Rain Garden Installation. Here is an example from my own front yard. Yes, my rain garden is in the front yard along with my 500 gallon cistern. I am available for consultation and/or design. Help us conserve stormwater!