Standing water can cause big problems on your property: dead grass, leaky foundations, and a potential mosquito paradise if rain water fails to soak into the ground. Fortunately, there’s a way to help that water infiltrate instead of leaving it to pool atop your lawn.  

A rain garden can help solve flooding problems on your property, and at the same time, add attractive landscaping to your yard and provide habitat for birds and butterflies! You can create a rain garden by digging a shallow basin in your yard and planting it with native plants that soak up rain water.  

We’ll run you through the basics of making a rain garden so you’ll know what to expect if you decide to add one to your property.  

Is a Rain Garden Right for You? 

Many homeowners can benefit from a rain garden. Most notably, rain gardens can be part of the solution to solve minor water drainage issues on your property and in your community.  

On the other hand, maybe rain water runs off your yard instead of pooling. In this case, a rain garden will protect rivers and streams from pollutants that runoff brings into local waterways. Instead of running off your property, stormwater will collect in the rain garden and slowly soak into the ground. This restores clean water to underground reserves and prevents water pollution in local rivers due to runoff—a double win for clean water! 

Find the Right Place for Your Rain Garden 

There are a few considerations to keep in mind when placing your rain garden. To start, you should place it near a downspout so that water collected from the roof will be directed into the rain garden. However, make sure your rain garden is at least 10 feet away from your home to make sure infiltrating water doesn’t drain towards the foundation. You can also choose to set it back farther from the house to collect water from both the roof and lawn.  

If possible, it’s best for the rain garden to be on a gentle downward slope so water is directed away from the house and into the rain garden. Also, choose an area in the yard that gets full or partial sun. Rain garden plants need some sunshine to survive! 

Sizing Up Your Rain Garden 

The size of your rain garden depends on a few factors, especially your property’s soil type and the size of the area draining into the rain garden.   

Soil 

Sandy soil will infiltrate water much faster than soil with a high amount of clay. In general, this means that rain gardens in areas with clay-heavy soil need to be larger to account for slower water infiltration.  Heavy clay soils may need to be amended to increase organic matter to help the plants grow. More details on soil amendments can be found in the University of Wisconsin-Extension’s rain garden guide

Drainage Area 

You’ll then need to figure out how much area drains into the rain garden. The bigger the drainage area, the bigger your rain garden should be.  

If you plan for your rain garden to be close to the house, the water will almost entirely come from the roof. Therefore, you can find the drainage area by calculating the roof’s surface area. Then divide that area by the number of downspouts you have, assuming only one downspout is directed into your rain garden. 

If you plan to place your rain garden more than 30 feet away from the house, you’ll have to add the lawn area that will drain into the rain garden to the roof area. 

Once you’ve figured out your soil type and drainage area, you can reference the “Using the Rain Garden Size Factors” section in the University of Wisconsin-Extension’s rain garden guide to find the recommended size of your garden. 

Depth 

Rain gardens are typically between 4 and 8 inches deep. You’ll want to make the rain garden level for the best infiltration. You’ll also find specific suggestions on rain garden depth for sloping areas in the rain garden guide.  

Steps to a Successful Build 

While we won’t go into much detail here, the main steps to building your rain garden are to dig out soil to your chosen depth, make sure it’s at a level depth, and create a berm along three sides of the rain garden. To make it easier to dig your rain garden, you’ll first want to kill the grass in that area. To do this, we recommend you place black plastic or cardboard over the lawn until the grass dies. 

After digging the rain garden, you’ll want to make a berm around it. A berm is a low, sloping wall or ridge of compacted soil on three sides of the rain garden that keeps the water in the rain garden.  Use the soil you dug out to create the rain garden and pile it along the sides, leaving the side near the downspout open. The berm should be tallest on the downhill side and taper off on the other two sides. Once you’ve shaped the berm, stomp on it to compact the soil.  

Planting the Rain Garden 

Make your rain garden functional and attractive through the selection and arrangement of native plants! To create an attractive landscape design, consider the bloom times, flower color, and heights of the plants. Layout the plant plugs to finalize the arrangement and then plant the plugs. Next, apply finely shredded mulch, leaving some room around the base of the plants.  

Some native plants suitable for rain gardens include swamp milkweed, fox sedge, and New England aster. A diversity of native plants, including native flowers, sedges, rushes, and grasses, creates a deep and dense root system and supports wildlife like birds and butterflies. 

Maintaining Your New Rain Garden 

Now that you’ve built and planted your rain garden, you’ll have to do some maintenance, especially in the first year. 

Immediately water the plants after planting them and continue to water them once a week until they are established. After that, you won’t need to water them often. Our native plants can survive dry spells and will get plenty of water when rain collects in the garden. 

You’ll also need to weed the garden as the native plants are growing. After a couple years, the plants will fill in and leave less space for weeds. If you prefer a more manicured look, it’s best to remove seed heads, occasionally cut back new growth, or dig up spreading rhizomes to slow plant growth.  

For more detail on building a rain garden, plant suggestions, and sample garden plans, view this in-depth guide from University of Wisconsin-Extension and Wisconsin Department of Natural Resources.