How to Build a Rain Garden

by BrendaReeves

A rain garden is a plant pond or garden bed used for channeling rain water away from the foundation of the house.

Too much rain can undermine a home, but a rain garden will easily solve the problem. The rain garden is planted with special deep rooted species of plants that help the water rapidly seep into the soil. The rainwater flows from the downspout and is directed away from the house and out of the lawn via a swale/stone channel. The garden bed captures the water and drains into the soil quickly.

An added advantage is mosquitoes won't have time to breed, because the water drains within a day. This also reduces the load on the sewer system, and the amount of lawn chemicals and pet wastes that would otherwise have drained into the sewer system making its way to rivers and lakes.

A Small Rain Garden
A Small Rain Garden

Design and Build the Rain Garden

In order for water to flow into the rain garden, there must be a minimum slope of 1 inch in 4-1/2 ft. (2 percent). If the slope doesn't exist, major landscaping will have to be done to create the slope and improve drainage.

The first step is to find a location for the plant pond. The rainwater must flow into it from downspouts, driveways or low points in the yard. Next, lay river rock for the swale. The rock should be at least 1-1/2 inches in diameter. Larger rocks may be used if desired.

PVC pipe may also be used. If the garden is more than 30 ft. from a downspout, PVC is the best choice.

Place the rain garden at least 10 ft. away from the house so water doesn't saturate the soil close to the foundation or back up against it. If water is already pooling close to the house, channel it with underground PVC pipe.

Create an overflow for the garden. This is an area on one side slightly lower than the garden that will channel the water away when the garden fills. Be sure to locate it away from the house and the neighbors' house as well.

Be careful not to locate the garden over the septic tank or underground utility lines.

A Nicely Designed Rain Garden
A Nicely Designed Rain Garden

Depth of Garden

The garden should capture only enough water to drain through the soil in 24 hours after a storm. Sandy soil will drain very quickly. Clay soil drains much slower. To test the porosity of the soil, dig a hole in the garden area about the size of a large coffee can and fill it with water. Ideally, the water should drop 1/2 inch in one hour which means or an inch in two hours. At that rate, the soil will handle12 inches of water in a 24-hour period. This makes the ideal depth of the garden 12 inches.

Plants for the Rain Garden

The best plants for the rain garden are indigenous, because they will thrive in that zone. Native grasses, wildflowers and shrubs have deep root systems. Plus they cast off their roots annually and grow new roots thereby providing more aeration and pathways for water to flow. With that said, plants for this type of garden are fairly standard:

  • Aster
  • Daylily
  • Iris
  • Sedum
  • Coneflower
  • Artemisia
  • Sedge


The First Year of Your Rain Garden

The last thing a homeowner wants is a problem with a wet foundation or basement. The rain garden offers a solution. The first year the rain garden is built it's important to mulch with shredded hardwood mulch. Other mulches will float away. Don't forget to weed regularly. Also, during the first year, dig a notch into the berm on the low side of the garden to let about half of the water flow out. Young plants can't tolerate a large volume of water. Add large decorative rocks at the garden's entrance to keep heavy rain from washing out young plants. Water about an inch per week during dry spells. After that, sit back and enjoy the garden without giving a wet foundation a second thought.

Updated: 09/23/2012, BrendaReeves
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BrendaReeves on 06/26/2016

Thank you, CruiseReady.

CruiseReady on 04/03/2016

What a lovely - and practical - addition this would be to a landscape. And Iris is one of my favorite flowers. Unfortunately, we live in a very 'flat' area, with sandy, fast draining soil, so I'm not sure it would work for us. Maybe that's why I've not seen one around here. I'd love to see one, though!

BrendaReeves on 10/23/2012

Thank you Katie. You'll have to take a picture and show us.

katiem2 on 10/23/2012

Yes, I think I have the perfect spot for my rain garden, shall have one by next spring... love this idea so much gotta pin, and tweet now....again :)K

BrendaReeves on 10/02/2012

Thanks for the comment Lil. I should build one in my backyard. It slopes toward the house.

katiem2 on 09/25/2012

OMG, I love this idea, you know I have got to have a rain garden now. It's beautiful. I'm so showing this to my landscape guy! Thanks Brenda! :)K

dustytoes on 09/25/2012

I'm not familiar with these types of gardens, but I do have a similar set up out front. It's not nearly as fancy looking though.

happynutritionist on 09/24/2012

Have never heard of a rain garden before, what a practical way to make use of water in areas where there is enough rain.

Mira on 09/24/2012

This is very useful info for anyone looking to create a rain garden! I don't have a place for it, but I enjoyed reading about it :-)

Ragtimelil on 09/24/2012

I was going to build one or two of these when I had my house. It was on a major slope and every spring I had little waterfalls by the house. Great spot for one. What a great concept!

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