A rain garden is a natural or man-made depression that has been planted with native plants that are able to gradually absorb and filter storm water. Rain water from roofs, driveways, and other hard surfaces drains into the depression and then has time to be absorbed into the ground. This prevents runoff from entering storm drains or surface waters, which can lead to pollution and erosion. The purpose of a rain garden is to improve the quality of nearby bodies of water. Planting one in your yard is a great way to contribute to water conservation. It will also create a new environment for attracting birds and animals to your yard.
The location you choose to put your rain garden in is very important-
- It should be 10 feet or more away from your house.
- It should be at least 50 feet away from septic systems.
- A sunny location is preferable over a shady one.
- If you have a depression in your lawn where water naturally pools and sits, it is not recommended to put your garden there- you want your garden to be able to absorb the water that it collects.
- If you have a depression in your lawn that collects, but absorbs water, this is an acceptable spot.
- An area that has a 12% slope or more will be difficult to level.
After you have decided on a location for your rain garden you will have to mark out its size and shape. Typical rain gardens are 100-300 square feet. Many people decide on the size based on the availability of space they have. If you would like to get very in-depth with it, you can purchase books on how to calculate the best size garden for your area. These calculations will take into account where you live, the type of soil you have, the size of your roof, among other things.
The shape of your garden can be laid out using a garden hose. This allows you to play with the shape until the desired one is reached. Tear drop and bean shapes are popular choices for water gardens.
Digging the Garden
Digging the garden is, by far, the most physically demanding aspect of the job. Start by installing an edging to prevent the grass outside your garden from creeping in before the plants are established. Then, remove the sod from inside the edging. Once the sod is removed, dig a gradual shallow depression approximately 6 inches deep. The sides should be slightly higher than the middle.
Amending the Soil
If your soil is heavily clay based or is not naturally well draining, you will have to amend the soil. If you don’t, the water that collects will not be able to absorb into the water and will just sit there. This can create a breeding ground for mosquitoes. Rain gardens with proper absorption rates will not contribute to mosquito breeding. A typical soil mixture for rain gardens is 20% sand, 20% compost, and 20% topsoil. This is simply a guideline and will depend on what type of soil you have already.
Adding the Plants
The best types of plants to use are ones that are native and non-invasive. They should be able to handle the stress from brief periods of pooling as well as dry periods between rainfalls. Try to choose a variety or plants with large root structures. This will make your garden more effective and less susceptible to disease. In a rain garden you should not plant seeds, if possible. Seeds will have a hard time establishing themselves in the fluctuating conditions and may even wash away after a heavy rainfall. Buy plants from your local garden centre instead.
Here are some suggestions for plants to use in a rain garden in Manitoba:
- American elder– full sun to part shade
- Bee balm– full sun to part shade
- Black alder– full sun to part shade
- Blue lobelia– full sun to part shade
- Blue vervain– full sun
- Cardinal flower– full sun to part shade
- Marsh marigold– full sun to part shade
- Quamash– full sun to part shade
- Red osier dogwood– full sun to part shade
- Royal fern- part to full shade
- Swamp milkweed– full sun
- Winterberry– full sun to part shade
Be sure to visit our outdoor sales yard to see what other plants are available!