What's a Rain Garden?
A rain garden is built to hold and drain the water off of your roof and driveway. The plants in the garden are chosen because they can stand to have wet feet during rainy periods but are drought tolerant the rest of the year.
Rain gardens are valuable in returning rain water back to a natural distribution. When rain water is collected and sent down a storm drain, it more quickly reaches rivers and streams and increases the chance of flooding during rainy periods. The rain water also takes many pollutants from roadways and drainoff from yards into the storm drain system. Unlike sewer water that is processed before going back into our rivers and streams, storm drains go directly to the natural waterways.
With a rain garden, rain is collected in the garden and quickly drains away into the soil. The soil naturally filters the rain water and slowly returns the moisture to waterways. Many of the pollutants are processed by the plants in the bottom of the rain garden. Other pollutants filter into the soil and are absorbed.
I first read about rain gardens a couple of years ago when I was surfing for some other garden idea. I was fascinated by the idea but also wanted it to look natural, not like a circle in the middle of my front yard. I spent a year researching the garden and in the fall of 2007, we built a rain garden which included native plantings to form a thicket and many drought tolerant flowers to fill the area.
The thicket is comprised of native shrubbery to attract birds, butterflies and other insects. We added a dry stream bed to bring the water away from the house and down into the actual rain garden drainage area. Then filled the remainder of the area with flowers that were drought tolerant and nectar producing. The end result was our new beautiful front yard.
After the garden was in, I started reading more about food forests, creating layers within a planting area and allowing groundcover to fill in the soils natural tendency to grow something. This year we decided to let most of the "weeds" in the form of clovers, birdsfoot trefoil and dandelions grow. These plants not only cover the ground as groundcovers, they also feed the soil by drawing nutrients from deep within the soil and making them available to the plants growing nearby. In addition, by having a groundcover layer in place, it helps to retain moisture, thereby helping the plants survive our long dry summer season.
The garden now has a bit of a wild feel to it. We'll be leaving the dead flowers and stems in place throughout the winter as further feed and habitat for birds and insects. The garden was watered about every 4-6 weeks this summer. Next summer it will be on its own and relying strictly on natural rainfall and whatever is stored in the ground.
If you would like to consider putting in a rain garden, I'd recommend contacting your local county extension office. There may be concerns in some areas regarding soil stability or water levels that may be important to take into consideration. If rain gardens are a viable idea in your area, they may also have resources to assist you.
Rain garden resources
Rain Gardens: A how-to manual for homeowners
This is actually a pdf file that was invaluable in the actual construction of the rain garden from the Wisconsin Department of Natural Resources.
It's important to note that I live in the Pacific Northwest. I found some local information for the best plants, but the basic information provided throughout this site is applicable for all rain garden building.