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A better way to drain rain

Reducing runoff with gardens and barrels

We’re experts at reshaping the environment to work for us — building roads and sidewalks, greening our lawns and whisking away rainwater so that it doesn’t flood our nice setup.

But all that runoff carries with it nutrient overloads and other contaminants that go straight into our streams, bypassing nature’s system of filtering water through plant root systems and storing it in the ground.

Installing a rain garden can help restore that system, according to Pam Bennett, an OSU Extension educator. She said rain gardens are simple and low-maintenance — and can even reduce the amount of lawn you have to mow.

What is a rain garden?

It’s simply a site with good drainage that collects the storm water from sidewalks, driveways, parking lots and gutters. Plants in a rain garden use what water they need, then allow the rest to return to the water table, Bennett said.

Where should you put a rain garden?

Find a low spot in your yard that tends to get damp or collect standing water after a rain. You can also try to strategically locate the rain garden in spots where it will intercept runoff, as near a driveway or in the yard between a sidewalk and road. Bennett said the key is that it needs to be a place where water will run naturally (or with a little encouragement).

How big should it be?

Take into account the size of your house and the amount of paved surface you have.

A rough estimate, Bennett said, is that 1 inch of rain on a 1,000-square-foot roof will amount to about 623 gallons of water. So the bigger your roof or parking lot is, the bigger you’ll want to make your rain garden.

The idea is to have a space that will hold the water temporarily and drain it into the ground within 24 hours. You don’t want standing water that kills plants and provides a place for mosquitoes to breed.

You don’t want standing water that kills plants and provides a place for mosquitoes to breed.

How do you prepare the ground?

While it’s fine if water collects during a heavy rain, it needs to drain afterward.

“One of the really important things about a rain garden is that it drains well,” Bennett said.

Remove the grass or kill it, loosen the soil, and dig down about 12 inches to work in organic matter such as plant compost or composted manure, peat moss or pine fines mulch.

What plants thrive in a rain garden?

Some people prefer to use native plants, but that’s not always necessary, Bennett said.

You want plants that can tolerate standing water from spring rains or dry periods during the summer. These can include trees such as red maple, bald cypress, river birch or sweet bay magnolia.

You’ll also want smaller shrubs and ground cover plants that will come back year after year, so you don’t have to replant. These can include spicebush, maidenhair ferns, lady ferns, liatris, pussy willows, little bluestem (an ornamental grass), summer sweet clethra, purple coneflower, day lilies, yarrow, asters and hostas.

Some rain garden plants also can have the dual purpose of attracting butterflies and pollinators.

How are rain gardens designed?

Some people focus on functionality, but you can put effort into a design and make it look nice, Bennett said. Think about how your plants will look once they grow to full size, what colors they will be in the different seasons and what time of year they’ll bloom.

What other alternatives are there to making rain work for you?

Rain barrels have the same function as rain gardens in that they stop runoff, but they also have the advantage of saving that water so you can use it to water flowers, for example. They may be especially attractive for people in a city who want to save on their water bills.

Rain barrels are set up to catch water running off a roof. However, that leads to a downside: You shouldn’t drink water from a rain barrel, Bennett says, and she doesn’t recommend using it in vegetable gardens either, especially on leafy plants such as lettuce.

Rainwater can pick up contaminants from roofs and houses, like old lead paint, asphalt or even copper.

You can buy a rain barrel or build your own — a number of online resources lay out how to make one out of a plastic barrel or trash can.