Runaway rain. That’s what you’re likely to see the next time the skies open up. Rather than streaming through your eavestroughs into the garden and saturating the soil, precipitation tends to run off your roof, travel across hard surfaces such as driveways and make its way to the street and sewer system.
This type of water is known as stormwater runoff, such water drains into nearby lakes and streams where it negatively affects water quality and hurts aquatic life. Runaway rain and snow melt often picks up toxic substances along the way like heavy metals, oils and road salts. Escaped precipitation is also a waste of water that could be corralled to stay in your landscape and water your plants.
What to do? Build yourself a rain garden. Such a planted or stone-covered bed keeps water in your landscape, allowing it to be absorbed and processed. The resulting captured water is cleaned of pollutants by your plants and replenishes the water table.
Locate your rain garden where it receives roof water from a downspout or runoff from a driveway or other hard surface. The best site location
is often the lowest point in the yard, as that’s where water tends to flow. You can position your rain garden on or below a down-slope, however, make sure the area is at least 3 meters away from your home or septic bed.
Pay special attention to soil preparation. Compacted soils are impermeable and won’t allow water to penetrate. Loosen all soil types by digging down 15 cm. If the soil is high in clay, add 25 percent coarse sand and loam. Bulk up sandy soil with compost and wood chip mulch.
Use any excess soil as a result of digging and amending to create a raised border around the bed. Such an elevated edge helps keep the water in the rain garden.
Check the effectiveness of your soil preparation by testing the drainage speed of your rain garden. Fill the area with water and wait 24 hours—after which time all of the water should have drained. If there is still water in the rain garden after this time period, re-dig the site to 20 to 25 cm and add additional amendments. Repeat the drainage test.
Capturing as much storm water as possible requires creating a garden 1.5 times longer than it is wide. If this is impossible, design the garden to as close to these dimensions as possible. Within these parameters, devise any shape that suits you and your garden—from square, to round, to kidney-shaped.
Ensure the health of your rain garden and create a captivating focal point in the landscape by choosing plants appropriate for the site. Given the nature of a rain garden, it’s important that the types of plants you choose tolerate both wet and dry conditions, so make your selections carefully. Native plants
adapted to your area's climate are often an ideal choice.
If you prefer not to worry about caring for plants, create a rock rain garden instead. After completing the soil preparation, simply line the garden with loose, hard items like river rock, pebbles or gravel. When it rains, such a garden looks like a stream bed. Make the rock garden more visually appealing by lining the perimeter with a decorative material like brick and adding a focal point in the center of the garden, such as eye-catching statuary or a large rock.
Whatever type of rain garden you install, pat yourself on the back. It’s satisfying to know that thanks to your charming new garden, you’re making a positive contribution to your local water quality.
By Julie Bawden-Davis