Information on designing and starting a rain garden were presented Saturday during the Northwest Ohio Agricultural Expo, organized by the Ohio State University Extension — Henry County, at the Henry County Fairgrounds.
Amy Moore and Allison Grimm of Fulton Soil and Water Conservation District recently attended a workshop on rain gardens, which can provide a means of filtering polluted rainwater, and shared information on designing and starting a rain garden. A rain garden was started by the district near its office in Wauseon and it has been certified by the River Raisin Watershed.
A rain garden is located in a depression in the ground filled with compost and soil that filters stormwater, while native, wet-tolerant plants create a habitat for pollinators.
“Rain gardens are really good at filtering out pollution, whether that’s in town along the streets or sidewalks, there’s debris that can get caught in storm drains, any other type of oil and things that,” Grimm said. “Rain gardens are very good at filtering, (and) they can also recharge our groundwater, which is what feeds our drinking water wells.”
Grimm noted additional benefits can include reducing pooling water on sidewalks, reducing water in basements caused by improper grading, reducing wet spots where mowers can become stuck and mosquitoes breed and providing healthy gardens that attract pollinators.
Choosing a location to start the garden is important, including selecting a spot downhill from a downspout or in an area where rainwater can be collected, staying at least 10 feet from buildings, avoiding tree roots, avoiding septic tanks, leach fields or wells and avoiding property lines and utility lines. Grimm added an important thing to keep in mind is that rain gardens are designed to overflow.
Moore added taking accurate measurements of nearby buildings or houses, driveways, garages and trees is important before beginning the design of the garden, which she suggested by done on draft paper. Within those measurements is also determining the amount of water that will be entering into the garden.
“The roof that you have on your house, for example, is the impervious surface where water is hitting,” she explained. “So you’re going to calculate the area — the length times the width — and from that, you can get the square footage of … the size of the rain garden to handle that much water.”
Grimm added there a variety of colors that can be designed with the plants, but it’s important to keep in mind the moisture needs.
“You want to keep in mind their bloom time throughout the year and their height,” she said. “Also, different plants require different moisture than others. So the plants that prefer the wet soil, you want to put more in the bottom of the rain garden, and then the plants that you know want a little bit drier soil towards the top of the rain garden.
“One thing that we always promote is to plant native,” she continued, “so there’s a lot of food available for the pollinator.”
Designing drainage is also an important part of the process.
“You can either have above ground drainage or below ground drainage,” Grimm said. “Below drainage is a little more involved. That’ll typically include digging below ground and putting in some sort of an outlet height where the water will essentially percolate through the brown and then empty out to a lower location you can have water running off on top of the ground.”
Once the design is complete, work can begin on outlining the garden border, tilling or killing off sod, digging a shallow depression with a level bottom if there’s not one there already, building a berm with a notch for overflow water, adding soil amendments such as compost, mulch or stone and planting.
Taking care of the garden is also important, including watering, weeding, fertilizing, mulching and thinning if necessary.
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