Rain gardens have a strong and growing reputation among environmental advocates and some local governments as a cost-effective, successful method of beautifying communities and reducing water pollution.  What are the rain garden facts most important for both types of communities to know?  We asked Patricia Pennell, a leading rain garden advocate, to help us answer that. Key points:

  • There is a 15-year body of evidence demonstrating conclusively that rain gardens are more effective than traditional stormwater management methods in preventing water pollution and reducing peak storm flows to rivers and lakes.
  • Federal, state and local water quality regulations are a significant impediment to the installation of rain gardens.
  • Homeowners and neighborhoods where rain gardens are installed who are initially skeptical soon learn to value and support them.

Pennell is one of the Great Lakes region’s leading experts on rain gardens and a former, longtime staff member of the West Michigan Environmental Action Council. In addition, she is a professional photographer with a keen eye for natural beauty.

How did you find out about rain gardens?

When someone asked me in the 1990s if I’d heard about them, I said, ‘No, but what a lovely thing! What are they?’  I got on the Internet and discovered that rain gardens are landscaping features designed to help protect water resources by managing stormwater. I was immediately hooked, as I’m both a botanist and a river lover, and enjoy the bountiful pleasures of the Great Lakes. I thought rain gardens would be a great way to protect the waters of this region. In addition, they had such a charming name; I thought rain gardens would be an engaging way for people to learn about stormwater pollution.

Were you right about that?

Yes. Today, a decade after I started a rain garden program in Grand Rapids, Michigan, rain gardens have been embraced throughout the Great Lakes region by individuals, nonprofits, schools, conservation districts, universities, extension service, municipalities, businesses, engineering firms, green builders, Habitat for humanity, landscapers, the EPA. You name it.  This is happening not only here, but all over North America, and — this is exciting! — all over the world. Rain gardens have taken the planet by storm.

One of the things people like best about rain gardens is their versatility. Rain gardens can be any size, shape or depth.  Almost any homeowner can plant some pretty rain gardens on their property. Schools and nature centers have joyfully embraced rain gardens for their ability to create wildlife habitat and protect water while engaging and educating students and visitors.

In cities and suburbs, rain gardens are designed by engineers to manage, clean and filter polluted stormwater runoff, and are then cleverly disguised as beautiful perennial gardens by professional  landscapers.  Ugly detention ponds full of dirty water, weeds and trash can now be replaced by pretty flowers, shrubs, trees, and butterflies. Stormwater runoff is reduced and waterways are cleaner. Everyone loves rain gardens; they’re feel-good gardens with benefits.

I learned ten years ago from Larry Coffman in Prince George’s County, Maryland and from Dr. Allen Davis at the University of Maryland that rain gardens absorb and slow down stormwater, and remove certain pollutants as well.  Dr. Davis and many other researchers now have a fifteen-year body of work that documents what rain gardens can do for water quality.

Are rain gardens difficult for homeowners to install?

No. They’re actually an easy thing to do—it’s just a garden where you send stormwater. Loose soil, pretty flowers; it’s fairly simple, creative and satisfying. For those building rain gardens on a commercial scale, it’s a little more involved. Stormwater engineers are used to putting things into pipes and ponds, and have fancy calculations to figure those out. Working with rain gardens is still fairly new to many. However, in recent years manuals have been created to educate and guide professionals in rain garden and other low impact development design.

Every rain garden is site specific, so there’s no “cookie cutter” rain garden the way there are “cookie cutter” pipes and drains. Engineers have to expand their traditional horizons to design a successful rain garden. They must take into account surrounding drainage patterns that affect the site, replace a volume of soil, have an overflow plan, perhaps an underdrain, put in a drain cleanout if needed, understand the existing soils, stage construction correctly, and see the big picture. The simplest way for an engineer to understand the concept is that the rain garden has to work without the plants. The plants make it work better, and also make it beautiful.

A frequent obstacle for commercial rain gardens has been regulation. Many communities have stormwater management specifications that are not yet up to speed with rain gardens and similar types of green stormwater management. This can make it daunting for builders and developers who want to construct rain gardens. They may be required to put in traditional stormwater management infrastructure along with the rain gardens, leading to costly projects. Until a regulated community has some hands-on experience with rain gardens and trusts they will work as intended, this may not change quickly, although the free manuals are helping to solve this problem.

What are some of the problems?

Rain gardens aren’t pure magic; any garden without maintenance soon becomes an unsightly bed of weeds. In urban rain gardens, it’s best to use an obvious, more formal design and then treat it like any other perennial garden—weed, tidy it, and keep it looking pretty.

It can be difficult to keep a rain garden tidy when caregivers are unfamiliar with the recommended native species of plants. Learning about native plants expands landscape caregiver’s skills and knowledge, and gives designers a new palette to work with.

Rain gardens are here to stay, and I’m glad to have played a part in helping them become a household word. They’re still growing, and I still love them.