Rain Gardens: Waterwise and Easy on the Eyes

"April showers bring May flowers," is something you’ll likely be hearing all this month. But really, the more truthful phrase would be “April showers bring stormwater runoff and pollution to nearby streams and waterways.” Admittedly, this phrase is much less catchy.

Stormwater runoff really is a problem in many urban areas. It is a major source of water pollution, and it wastes tens of thousands of gallons of usable water by sending it down the drain. There are a few different ways to counteract this, but one of the most aesthetically pleasing ways is to build a rain garden.

Laura Wilson, a 4-H science professional from the University of Maine, describes a rain garden as “a landscape feature that consists of a depression in the ground that is planted with water-loving native perennials and shrubs. The soil that fills the depression is mixed, to allow more water below the surface. Water from a downspout or other source flows into the rain garden, where it soaks into the ground and is absorbed by the plants within a certain amount of time.”

As for how that combats stormwater runoff, Wilson adds, “The water that would otherwise have run off elsewhere is captured and collected, so it doesn’t add to stormwater quantity issues. Plus, any pollutants from rooftops or other hard features go into the garden. Nutrients from the runoff are used by the plants in the garden itself, and sediment is captured in the bed of the garden.”

Rain garden installation isn’t only great for the environment, but it’s also a great option to offer to your clientele. Eco-conscious clients will definitely be in favor of using water that came from Mother Nature and reducing pollution. Also, aesthetically-concerned clients will like the attractive design.

Plus, if you work in areas where rainfall is heavy and sewer systems are insufficient, there will often be government money going into your work. However, along with that government money comes the need for certification. While programs differ across the country, you will need to apply for certification and be up-todate on the rules and regulations of stormwater management, in order to offer rain garden installation.

“There are a lot of hoops to jump through, in terms of paperwork,” says Edward McHugh, a RainWisecertified landscape contractor and owner of Acorn Landscaping in Seattle, Washington. “The RainWise program we have in Seattle is funded by government funds, so everything has to be documented and installed by trained licensed contractors in order to participate in the rebate program that we have in this city.”

Even so, that little bit of homework has a big payoff. Rain gardens are fairly easy to install, and the extra service can push you in front of your competitors.

One of the first things to consider is where you’ll put the rain garden. If you’re familiar with your client’s property—or if there was recently a rain storm—then you’ll want to seek out where the most water accumulates. More often than not, it will be near gutter drains. But make sure to keep the garden more than 10 feet away from the house or any other structures, so as to avoid water problems in basements or foundations. If needed, you could transfer the water from the gutter to the garden with pipes.

If you are not familiar with the property, then you may have to do a percolation test. Drill or dig a few six-inch-deep holes into various points in the property and fill them with water. Leave them lie, then examine the holes 24 hours later. The holes that have completely absorbed the water within that time are the areas best suited for the rain garden.

As for size, you’ll have to do a bit of math. The general suggestion is to divide the square footage of impermeable surface on the property— such as driveways and roof tops —and divide by six in order to figure out how large the deepest part of the garden should be. If you have several houses in the same neighborhood, you’ll be able to keep your measurements roughly the same.

As you’re planning out the size of the garden, you should also figure out the zoning of each level. Your average rain garden will have three main zones. The deepest zone, directly in the center, will be about sixinches deep. This is where the majority of the water will gather during storms. While you could make it deeper, six inches is the deepest that most plants can be submerged without drowning. Your next zone will taper up from the center to the third zone, which is level with the original area.

Once you figure out where the zones will begin and end, it’s time for the muscle work. You need to start digging. You can use heavy equipment, especially if you’re working in a commercial lot. But in residential areas, you’ll be better off just using a shovel and some elbow grease.

Now, unless your clients have decided that they’d rather have a pond after all this, it’s time to fill the hole in. You’ll want to make sure the dirt doesn’t get packed too hard; after all, the purpose of a rain garden is for the water to easily permeate deep into the ground. Keep things loose by mixing the excavated soil with either clay or mulch, then spread topsoil over the newly-filledin hole.

Now comes the part that everyone will see—plants. Not only will they keep the area from looking like a big oval of dirt, but the root systems will keep the soil in place and prevent any washout.

But be sure to do your research as to what plants to choose. Droughttolerant plants will definitely not work in a rain garden. Instead, choose thirsty native plants; they’re better suited for the this.

“One of my favorites is osier, which is a hybridized version of a red-twig dogwood,” said McHugh. “Particularly one called Arctic Fire, which is a real showy plant in the dead of winter because it has a red, yellow and orange trunk. And it likes to sit in water. Some of the other ones are juncus patens, which you’ll find in ditches and soggy areas where the water sits most of the year. And there’s a variety of sedges and native iris, which all tend to like the water.”

Since the deepest part will have the most water, you’ll need to take care that the plants you install won’t drown or otherwise be negatively affected by having their roots sit in water for extended amounts of time.

Zone 2 plants, while they won’t be steeped in as much water, will still see a good deal of it if there’s a rainstorm. In Zone 3, though, any kind of plant will do.

“That’s where I bring in cultivated plants,” McHugh says. “I might bring in something that the homeowner likes or that already exists in the yard, to make a cohesive landscape.”

All that’s left to do now is mulch around the inserted plants, and your work is done. However, your client still has a bit of maintenance to do. While a rain garden will ultimately be a low-maintenance fixture, a homeowner will need to take care of it just like any other garden.

“Keep the weeds out, and make sure the plants have enough water until they’re established,” suggests McHugh. “It’s all the common things you do with your garden to make sure it does what you want it to and thrives, so there’s nothing really specific about it that would make it different from any other garden.”

Rain gardens are an efficient and beautiful way to ensure that water goes into the ground rather than running off into waterways. It will keep a majority of runoff from leaving a property, while replenishing underground aquifers. By offering this choice to your customers, you can ensure that their April showers will bring clean water with the May flowers.