The Garden Of Oz

Rain Gardens - What are they? And why have one?

If you’re looking for a new garden project that will improve both your little piece of the environment and the ecology around you, maybe this is the year to build a rain garden.

Background

Rain gardens have been around for a long time, but they’re becoming increasingly popular as more landowners become conscious of their impact on the overall environment. Rain gardens

are simply planned gardens that capture, and filter, rain water that would otherwise run off, or through, their property.

Rainwater runoff has become a more serious problem as both residential and commercial development has increased the quantity of impervious surfaces... roads, building roofs, patios, and other impenetrable areas that preclude rainwater from soaking into the ground that is now covered by these “waterproof” areas.

Increased rainwater runoff is the cause of a number of potential problems, including:

Increased pollution of streams and water supplies, as the rainwater picks up chemicals from roads, lawns, farms, and parking lots

Erosion of both surface soil and subsoil, sometimes resulting in sinkholes and structural damage

Reduction of the natural replenishment of groundwater supplies

These issues may be so subtle as to not be obvious; and, sometimes the problems created by rainwater runoff occur miles downstream from the cause.

Benefits of Rain Gardens

You can easily construct a small rain garden, with a minimum of effort or upkeep, that will benefit the local environment and improve the beauty of your immediate surroundings. Once established, rain gardens can be nearly maintenance-free and very attractive. Unlike water gardens, there’s no need to install special liners, and no issues with the problems associated with standing or stagnant water, like muck and mosquitoes, to name just two.

In fact, most people won’t even recognize that your rain garden is any different from any other well-planned garden. But, you’ll know that you’ve contributed to the environmental wellbeing of your part of the ecosystem, while enhancing the beauty of your little piece of the universe.

Your rain garden will not resemble the unattractive catch basins that are increasingly popular in commercial construction areas. You won’t need to put a fence around it, and you won’t be creating your personal little swamp.

The Basics

A rain garden’s purpose is to collect, filter, and keep the water that would otherwise run off of, or through, your property.

Typically, large or medium sized rain gardens should be located at least 10 feet from your house to preclude increasing the amount of water around your foundation. (Note, however, that having plants around the house will also reduce the amount of water that seeps into the ground around your foundation.)

Rain gardens should not be located immediately over a septic system, as these areas are already moisture laden.

Your surface of your rain garden should be 4 to 8 inches lower than the surrounding surface of the lawn, so that it will be able to trap rainwater for a short period of time, until it seeps into the soil, feeding the plants and filtering any potential pollutants that would otherwise run off the property.

How to Plan Your Rain Garden

Once you’ve selected the location, the next steps are very easy, and can probably be accomplished in less than a day.

First, decide how big your rain garden should be. The size of the ideal rain garden is a function of the total area of impervious surfaces on your property (roof, driveway, patio, etc) and the structure of your soil. Here’s a simple rule of thumb:

For very sandy soil, your rain garden size should be about 20% of the total area of impervious surface.

For loamy soil, the area should be about 35% of roofs, etc.

And, for heavy clay soil, you may need to have a garden that is equivalent to 50% of the impenetrable area.

Second, decide the shape that will fit your existing landscape and increase the aesthetic value of your property. Most rain gardens should be a variation of an oval design, as a long, skinny garden won’t really capture much runoff.

Third, decide what you’ll plant in your rain garden. The experts recommend “native plants” – that is, plants that are native to your area. These plants have demonstrated that they can thrive in your climate. Pick plants that can tolerate short periods of wet conditions, but also a couple of weeks of no rain at all. After all, you don’t want to have to water your rain garden, except in periods of extreme drought, once it is established.

While I was researching this article, I was delighted to find that there are a lot of web sites with specific plant recommendations for rain gardens in every area of the country. You can probably find a good list simply by going to Google and typing “rain garden plants for [your state].”

I was happy to see one of my favorites listed for New Jersey ...Daylilies... which I think are one of the more lovely additions to any garden. Many will bloom almost all summer, and they’re available in a wide range of colors and heights. They increase in size each year, and you easily dig them up and divide the roots to create new plants, or to share with gardening friends. One of my favorite daylilies was given to me by a friend who had dug his up and divided the roots.

How to Build Your Rain Garden

First, remove the sod from the area. Dig out any grass and weeds, roots and all, and compost them. You can store the grassy soil upside down for a few weeks to kill the grass and weed plants. Then, simply add them to your compost pile, or start a new one (always a good idea for gardeners!).

Second, add some compost to the dug out area. Four or five inches of compost will significantly improve both the fertility and tilth of the soil. If you own or can borrow a small tiller, this part of the job can be done in less than an hour. The tines on my Mantis tiller, for example, are especially good at mixing compost into the soil. Adding compost will improve both the growing conditions and the water absorption properties of your rain garden. If you’ve read other section of this site, you know how much I love compost. The rain garden experts do, too! For more on compost, visit Our Composting 101 article or http://www.howtocompost.org/

Third, plant “native plants” in your rain garden. A simple search will show you that you’re not limited to flowers … rain gardens can include trees and shrubs, too. Many trees and shrubs are ideal for rain gardens, because they develop large root systems that can absorb a lot of water, and they can tolerate a couple of rain-free weeks, as well.

Fourth, mulch the garden. Use a mulch that will allow water to penetrate and one that will help prevent weed growth. Remember, we’re going for a low-maintenance garden. This may be the one time that wood chip mulch can be useful. I use it very sparingly in my flower gardens, and never use wood chips in my vegetable gardens, as wood chips do rob the soil of nutrients that I’d rather have available for my vegetables. My first choice would be a thick layer of well pulverized brown leaves (Not walnut leaves, but oak or maple would be ideal).

Fifth, water the garden until it is well established. I know that this might seem counterintuitive. However, you do need to baby newly transplanted trees, shrubs, and flowers for a little while. Once established, however, the rain garden should be almost maintenance free.

More Information

I’ve included the basics here, but for those who want additional information, here are a couple of helpful websites that I recommend:

http://www.raingardennetwork.com/

http://www.rainscaping.org/

Get Started!

My advice is to get started! Start with a plan, of course, but get started. A lot of gardening is trial and error, and you might find that you want to change your plan later. If you’ve picked the right spot, that will be easy. Just remember, any rain garden is better than no rain garden. You can always make it bigger or smaller later.

And, while you’re at it, how about sending me a note, and perhaps a photo or two? I’d really like to hear from folks who have been motivated by reading this article.

Good luck with your new rain garden,

If you have any comments, I’d really like to hear from you.

OZ Gardener
The Garden Of Oz

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Reviews

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February 26, 2012

By: Cheryl Jones

Recently a landscaper friend, in MI, mistakenly sent an email to me about rain gardens. She says they are quite popular there and I should check them out.
I'm more familiar with bog gardening, now I understand that they are not the same.Your info has peaked my interest.
Thank you for pointing out to use native plants that are "native" to someone's specific area. What's native to my area here in TN are not likely native to Mary's area in NV.
Thank you,
Cheryl
www.greenwoodnursery.com

January 9, 2010

By: Peggy Mills

Thank you for the info, I too love the native plant idea.

June 18, 2009

By: Annette K

Great information on rain gardening. I'm going to give this a try!

May 26, 2009

By: Mary T

I'm so glad to see you covered native plants in your article. This is the big problem where I live in Nevada, people want to grow plants that won't make it through the dry period. They don't realize the amount of water they need and the plants just die. Then we get a great amount of rain in a short period of time and there is nothing left to prevent the run off. Our flash flood problems require a garden with a little more planning than the average rain garden. But your article is dead on. The first mistake people make here is not looking for native plants in the first place.