How to: Build a rain garden

Rain gardens have become more popular as a proven and effective way to decrease water runoff and soil erosion and increase a habitats diversity.

“The overall purpose of putting one in is to allow the runoff to infiltrate into the soil,” says Julie Evans, vice president at The Fockele Garden Co. in Gainesville, Ga. “What that does is it helps with ground water. It also filters the water before that water would reach our streams and lakes. It also helps clean our water as it percolates through the soil.”

Another beneficial aspect is that the plant variety can increase the diversity of insects and wildlife, which leads to a more balanced garden, Evans says.

The first step in building a rain garden is finding the proper placement so it catches the majority of the properties runoff. So that it doesn’t stick out like an eyesore, Evans says it’s best to blend it into the landscape design.

“From my point of view, I would want it to fit into the surrounding landscape with additional plantings,” she says.

– Carolyn LaWell

1. Determine where the rain garden should be placed. Factors to take into account are where the water runoff will easily reach the rain garden and how close the space is to the house or the building.
    
2. Specific calculations need to be used to determine how big to make the rain garden. Then the shape and depth can be decided. “It’s important to know how much water you need to intercept and infiltrate so you don’t have a washout,” Evans says.
   For a manual with the calculations click here.
    
3. Undertake the construction of the rain garden basin, which is primarily done by digging and excavation. “It has to be level so that when water runs into it, it can spread throughout the garden and not puddle in one place,” Evans says.
    
4. A berm should be placed around the rain garden to contain water, Evans says. The size of the berm will depend on the depth of the rain garden. “You need some sort of container around (the rain garden),” Evans says. “The dirt you excavate out of it you can berm up.”
    
5. Once the basin is shaped and level, plants can be placed and watered into the rain garden.
   “You want appropriate plants for a wetland in your area – a wetland that will also dry out,” Evans says. “Certain plants can do that.”

Illustration by Ron Wilson