What Is a Rain Garden and How to Make One?
Rain gardens are one of those rare examples of something useful, sustainable, economical, and beautiful. If you are not familiar with the concept of rain gardens, they may look like a small (in some cases), randomly located garden in someone’s backyard, but in fact the opposite is true. Rain gardens require planning, precision and, yes, a little math. Here’s what you need to know about rain gardens, including what they are and how to make them.
What is a rain garden?
First things first: A rain garden is a garden in which native shrubs, perennials and flowers are planted in a small depression in the ground, usually formed on a natural slope, the Groundwater Foundation explains. The purpose of a rain garden is to temporarily contain and absorb rainwater runoff from roofs, driveways, patios, or lawns. Sounds good, but do they work? We’ll let the Groundwater Foundation break it down:
Rain gardens effectively remove up to 90% of nutrients and chemicals and up to 80% of sediment from rainwater runoff. Compared to a conventional lawn, rain gardens absorb 30% more water into the ground.
Keep in mind that a rain garden is not a water garden, pond, or wetland. In fact, it is dry most of the time, except for a period of 12-48 rainfall, the Groundwater Foundation explains . So, unlike standing water areas, rain gardens do not give mosquitoes a place to breed.
Great, but what difference does it make to planting a garden in the back of your yard? In the words of Jeanne Huber in this old house :
Rain gardens allow water to collect during heavy rainfall and then slowly seep into the soil. A shallow drainage basin is more of a flower garden for water than a travel path like a canyon. The rapidly draining potting mix promotes water penetration and lush plant growth. Runoff can flow into the rain garden from a ditch or pipe, or it can simply drain from a sloping yard.
How to make a rain garden
Before you start digging, find a spot at least 10 feet from your home and at least 40 feet from a septic system or steep slope. Although there are several steps to building a rain garden, the project should take three to four hours. Here’s what you need to do, according to Huber of This Old House :
- Before you start digging, call the service department and mark all buried pipes and wires.
- Use some line paint to paint the borders for the rain garden.
- Use a shovel to scrape off any grass and roots in your garden.
- Dig 18 inches with a shovel and discard the removed soil. A pickaxe can be used to break open heavier soil.
- Add 1 to 2 inches of coarse sand to the hole and spread it evenly with a metal rake.
- Remove the plants from the nursery pots and replace them.
- Use your claw to pry off the roots and encourage them to grow outward.
- Fill the hole with a mixture of 1/3 coarse sand, 1/3 compost and 1/3 bark mulch.
- Water the plants thoroughly, then cover with a layer of bark mulch.
- Continue watering for a month until the plants take root, and then the plants should only survive on rainwater.
And what to plant in the rain garden? Huber recommends planting species that tolerate wet conditions – native sedges and god ferns – in the center of the garden, surrounded by plants that can withstand occasional standing water, such as red dogwood. Choose plants around the outside perimeter of your garden that prefer drier soil, such as native evergreen and deciduous shrubs.
For more information on the rain garden, this page of the EPA website probably has what you need.