A rain garden is a shallow depression in the ground that is typically planted with native grasses and flowers. Water from your downspout or driveway is directed to the garden, where it soaks into the ground instead of running to the street, to the storm drain, and then the river.
A rain garden isn’t a pond. Collected water usually soaks into the ground in a few hours. The garden is dry most of the time.
Commercial basins usually require the expertise of a professional landscaper, but home gardeners who deal with smaller volumes of water can easily design and build a sunken garden with the directions below and the guts to go for it!
- Call the power company to mark utilities (free).
- Choose a spot for your garden at least 10 feet from the house.
- Remove sod. Loosen soil. Mix in leaves or other compost.
- Dig the garden 3 to 6 inches deep.
- Make a small mound at the edges.
- Plant native plants in the basin.
- Add 3 inches of mulch.
- Aim a downspout at the garden.
SELECTING A LOCATION
- The most logical location for your rain garden is in an existing low spot in your yard.
- Place your garden where downspouts will drain into it, directing water with a shallow swale if necessary.
- Place your rain garden at least 10 feet from your house or other building to keep water from seeping into and damaging the foundation.
BUILDING A RAIN GARDEN
It’s simple! Follow three easy steps:
- Start by digging a 4 to 8 inch depression with gradually sloping sides as large in circumference as you like. A good rule of thumb is to size your garden at 30% of the area of the roof from which it will be collecting water. A 4 to 8 inch depth will capture water and allow the garden to dry between rains.
- Loosen the soil and mix in leaves or other organic matter.
- If you like, add a raised edge, stones, or a few big rocks for visual interest.
- A rain garden can have just grass or rocks in it, but native plants keep 30% more water in the garden. Of course you can buy plants, but talk with your neighbors first, to see if they have some that can be divided and shared.
- Use plants rather than seeds to give the garden a strong start, minimize maintenance, and keep weeds out.
- Plants that need medium to wet soil go in the deepest part. Plants that like drier soil go in shallower areas around the edges.
- Add 3 inches of untreated, shredded hardwood mulch on all of the bare soil around the plants to prevent erosion while plants are getting established.
- While your plants are establishing roots, water them about every other day. Continue for the first 2 to 3 weeks or until the plants are clearly growing and doing well.
- Weed well during the first 2 seasons. Well-established native plants minimize competition and future maintenance.
- Native plants need little or no additional watering once established.
- Do not fertilize native plants! Fertilizer makes them grow too tall and fall over. It also stimulates weed growth.
Thanks to Sue Ellingson and Mid America Regional Council for the information above.
SEE HOW TO INSTALL A RAIN GARDEN
Watch how it’s done! These folks get creative with a rock waterway and little bridge, but those are just frills. The important parts are digging a shallow basin, loosening soil, and directing water to the garden. Click here to watch the video.
UW-EXTENSION RAIN GARDENS MANUAL
For more detail, download this brochure from UW-Extension.