What is a rain garden?

A rain garden is an attractive garden with a special purpose—to reduce the amount of stormwater entering our beautiful streams, rivers and lakes. A rain garden is constructed as a place to direct the rain from your roof or driveway and is landscaped with plant species native to our region.

What makes a rain garden different from any other perennial garden?

• A rain garden is bowl or saucer shaped, not mounded or flat like other perennial gardens. It is not just a pretty garden; it is also designed with deep, loose soil, specifically to collect and absorb rain that would otherwise run off your property, and/or to solve wet spot problems where water is already collecting.
• Instead of using cultivated plants from Europe and Asia, a rain garden is planted primarily with deep-rooted, low-care, perennial plants native to your region, that have adapted over thousands of years to your local weather and conditions. The deep roots provide channels into your soil for water to travel into. The native plants provide habitat for local butterflies and other wildlife. The native plants do not need to be treated with chemical fertilizers, pesticides, or herbicides in order to thrive. A rain garden is a beautiful way to make your property healthier for your family and community, while helping to protect the lakes, rivers, and streams where you live.

Why a rain garden?

Stormwater carries pollution from yards, streets, and parking lots into the nearest body of water. One study showed that up to 50% of that pollution comes from things we do in our yards and gardens! By creating a rain garden on your property, you can help improve water quality in local streams, rivers, and lakes. You can use rain the way nature intended, instead of throwing this resource away. A rain garden is a natural way for you to help solve our stormwater pollution problems, help recharge groundwater, and protect our water resources.

In addition, rain gardens are attractive landscaping features. They feature native species of plants that are adapted to your region, and they can be low maintenance while providing habitat for native wildlife and butterflies.

Why is stormwater a problem?

We tend to think that large industrial polluters cause most water pollution, but this is not the case. We are the real culprits. The Environmental Protection Agency (EPA) has determined that up to 70% of the pollution in our surface waters is carried there by stormwater runoff. Some studies show that about 50% of that pollution comes from individuals and homeowners, due to yard care, yard waste, and chemical pollution from household activities.

When it rains, water runs off of our roofs, parking lots, streets, and lawns, instead of soaking into the soil the way it did before development. This water, along with everything it picks up along the way, ends up in storm sewers and ditches that discharge to streams, rivers and lakes. Salt from roads, pet waste, lawn nutrients, spilled gas, oil and other pollutants are all washed into the local waters.

In addition to carrying pollution, the stormwater runoff is usually warm, causing a pulse of warmer water to flow down the stream. In a natural system, water enters a stream through a slow and steady release from groundwater. Groundwater has a fairly cool temperature, which allows water to hold more oxygen and keeps stream habitat stable.  Many sensitive creatures such as trout cannot survive in a stream with fluctuating and warmer temperatures.

While groundwater release is slow and fairly steady, stormwater runoff occurs all at once. The large volumes of warm water flushing down a stream cause erosion and flooding, carry dam-forming debris, and scour the stream bed.

How is a rain garden constructed?

They can be simple—just a green area of your yard where stormwater goes—or complex, involving excavating and re-building soil. They also may be “industrial strength,” handling large volumes of water periodically, where large-scale stormwater management regulations must be met.

  
Where should I put a rain garden?

You can put a rain garden just about anywhere.

In a low area of your yard, a complex of plants and soil will absorb a lot of rain.

Generally you should avoid utility rights of way, where gas, phone and telephone lines are located. Also keep the garden location away from septic drain fields, which don't need any extra water.

If you have a problem with a wet basement, locate the rain garden away from building foundations. Ten feet away and downslope is a rule of thumb.

Every garden is site specific and unique—you can make it what you want to make it. 

Can I build one myself?

Yes. See our designs and construction information.

Where can I find someone else to build it for me?

Check our contact information for local resources in the "Where Can I Find" section of the website.

Will rain gardens breed mosquitoes?

No, not if properly constructed. Rain gardens are designed to absorb water, not to create ponds. In Michigan, a mosquito can develop from egg to biting adult in 7 or 8 days. A well-designed rain garden with mature plants will not have standing water in it after 48 hours; it will all have soaked into the garden.

Where can I see a garden?

Our demonstration site locations are listed in the "Gardens to Visit" section of the website.
 
Other projects may be in your area. When our regional directory is completed, check there.

What plants can I put in a rain garden?

Many beautiful plants, trees and shrubs can be planted in a rain garden. We recommend species native to to your region, but other cultivated non-native species can be very beautiful, too.  Michigan native species are adapted to our region, and should be low maintenance once established. See our plant information area for specific information and plant lists.

We do not recommend planting of invasive, problem species such as purple loosestrife.

Where can I find a rain garden project in my region?

If there is a similar project in your area, you may find their information in our regional directory, once this feature is completed.

Where can I find a technical manual on bioretention?

Prince George's County, Maryland, has kindly put theirs online in pdf files for anyone to download.

What about road salt?

It is better to locate the rain garden away from direct salt discharge. There are some salt-tolerant plants that you might use if the only place you can locate the rain garden will be subject to salt spray and runoff and from streets and sidewalks.

For large parking lot and street applications, pre-treatment structures may be helpful, such as a sediment settling area. For larger rain gardens for commercial parking lots, an underdrain system would be best; the salty runoff is filtered through the rain garden, then carried away by the underdrain system. This prevents groundwater contamination with chlorides.

Do rain gardens work in the wintertime?

Because plants are dormant, their activity is reduced, but the rain garden will still absorb water even in the winter. The ponding area provides storage for a certain amount of runoff even if the ground is frozen. Rain gardens do work best in the summer, but that is when they are most needed.

Can I pile snow on my rain garden?

You can place a small amount of snow on your rain garden, but a large amount may compact the soils in the garden or damage the plants. A glacier on the garden in early spring may slow down the greening of your plants. It is better to place large amounts of shoveled snow next to the rain garden; as it melts, it will flow in and be absorbed. 

How effective are rain gardens for stormwater education?

We think they are very effective, and popular, too. We are conducting an ongoing educational evaluation process, and the results will be available on this website.

Do I have to mulch my rain garden?

Organic mulch is recommended for formal rain garden designs. Mulch keeps the garden moist and able to absorb rain, makes the garden look tidy, and discourages weeds.  An application of hardwood mulch will look good, and compost mulches will enrich the soil. Large rain gardens or bioretention systems that are planted from seed are not mulched.

Where can I get rain garden designs?

Some are available on this website. Others are available at the Maplewood Minnesota rain garden site.

Where can I get rain garden plants?

Some rain garden plants are carried by many local perennial nurseries, as native species are becoming more popular for home and commercial gardening. Other rain garden plants can be purchased from native plant nurseries. Check our "Where Can I Find" area to locate sources for West Michigan. You may also choose to transplant some suitable plants in your yard, or you could get divisions from a friend.

Large quantities of rain garden plants must be ordered far in advance, as suppliers do not usually keep them on hand unless they have a ready market for them.

Please do not collect your rain garden plants from wild populations. They may be growing everywhere, but they soon won't be if they are removed from the local landscape. Purchase your plants from a reputable nursery that produces them in a sustainable way.

What is Rain Gardens of West Michigan?

Rain Gardens of West Michigan is a water-quality program of West Michigan Environmental Action Council in Grand Rapids, Michigan. For more information on the West Michigan Environmental Action Council, visit http://www.wmeac.org.

Are there rain gardens elsewhere?

There may be a rain garden near you. Check in our regional directory, when it is completed.

What is the history of rain gardens?

Rain gardens are a form of the “bioretention pond.” They were first developed in 1990. Read more about rain garden history here.