How To Make A Rain Garden

May 10, 2019

A cool, damp spring can seem troublesome for gardeners. But with the right kind of plants and gardening techniques, the weather can not only improve your garden, it can improve water quality. 

Lake Effect contributor Melinda Myers is the author of numerous books on gardening, including The Midwest Gardener's Handbook and Month-by-Month Gardening in Wisconsin. She explains how you can create your own rain garden. 

"The idea of a rain garden is to capture water coming off your roof, your drive, your patio, your lawn ... By capturing the water there, you're keeping it where it falls, and the plant roots and soil filter it before it goes down and recharges our ground water," says Myers.

The main things to consider are positioning, soil preparation, types of plants and maintenance. 

A swale (a shallow trench surrounded by a mound) leading into a drain.
Credit wlcutler / Flickr

Positioning

"We want it on a slight slope, away from the home. The last thing we need is more water by our foundation. At least 10 feet away from the foundation of your house, and then directing the water from your downspout into your rain garden," says Myers. 

You can do this by running an underground line or create a shallow trench surrounded by a mound (a swale), and you can add stones to direct the rain water into the soil. 

Soil Preparation

Adding organic matter, like dried leaves or mulch, is an important step in any garden. But for rain gardens, it's a necessary step. 

"Most of us in southeastern Wisconsin have heavy clay soil and it drains very slowly ... So, we want to add organic matter to help improve drainage," says Myers. 

Adding organic matter will also help those who have sandy or rocky soil, like those who live in the Kettle Moraine area. 

READ: Green Infrastructure Helps Manage Water In Milwaukee's Urban Landscape

(From left) Columbine, lavender hyssop, and swamp milkweed are all native to Wisconsin.
Credit koizumi, CAJC: in the PNW, & Brett Whaley / Flickr

Types Of Plants

It's a good idea to start with native plants, since they tend to do better in our climate and they attract pollinators. You want to arrange them based on how much moisture they can tolerate

"In the lowest part of your rain garden, it's going to stay wettest longer," she explains. 

In the early season, for shady areas or partly sunny areas, Myers suggests planting native columbine or lavender hyssop plants. For later in the season, she suggests swamp milkweed, which can work in both damp and dry areas. 

Maintenance

When starting a rain garden, you want to insure that the plants are getting enough water so they can take root. If it's a dry season, this could mean water the plants. 

"Check the top couple inches. If it's crumbly, it's time to water again," Myers says. 

If the season has been particularly rainy, you may find that there is standing water in the rain garden, which could be an invitation to pests like mosquitos. 

"You don't want standing water for 48 hours ... If you are getting standing water, then it's time to look at: is your rain garden big enough to handle the water? Maybe you need a second one," she says.  

"You don't want standing water for 48 hours ... If you are getting standing water, then it's time to look at: is your rain garden big enough to handle the water? Maybe you need a second one," says Myers.

For some, a second rain garden may not be an option. In that case, Myers suggests installing a rain barrel, so the barrel takes most of the water and the overflow ends up in the garden. 

If the plants are able to take root and are properly draining the water, you should be left with a healthy, sturdy rain garden. But since these are native plants, they may begin taking root in other parts of your yard. 

"Every few years you're going to need to dig and divide. You can start another rain garden with all of your plants, share them with your friends ... That's a great way to make your investment go even further," Myers explains. 

Myers suggests checking out Fresh Coast Guardians, if you want more information on starting a rain garden.