Rain gardens are a great way to protect the environment and showcase native plants

Delicate white flowers provide a beautiful contrast to the rich green leaves of the nannyberry. Fuchsia-coloured buds are beginning to form on the dwarf Joe Pye weed, and deep pink spikes of Astilbe complement the violet-blue flowers of the bee balm nearby. Marsh marigolds and milkweed provide a burst of yellow and pink against white lobelia flowers dangling over the raised garden border. To the ordinary eye it’s just another pretty garden, but this garden is far from ordinary.

Planted in a shallow depression, the garden has been carefully located to absorb excess storm water. Here, nutrients can be absorbed by native plants, and excess water is prevented from overflowing storm drains and sewer systems. In addition to redirecting water runoff from the street, the garden prevents contaminants such as road salts, fertilizers, and oils from polluting our water system, streams, rivers and lakes. This is a rain garden; a beautiful and simple garden that helps to protect our environment.

While rain gardens may seem like a new approach for dealing with drainage issues, bio-retention systems occur naturally in nature. Unfortunately, many of our natural forming wetlands and wet meadows are being destroyed by growing agricultural and urban development.

“Rain gardens are a great way to minimize the negative impact homeowners and commercial properties have on our environment”, says Chris Maxemuck. He installed a rain garden at his gardening centre in Lorette, Manitoba three years ago. “It has been a learning experience”, says the owner of C & S Country Gardens. Since then he has been sharing his knowledge and experience with customers and fellow gardeners.

Finding the right location is critical to success.

Sun or shade; it makes little difference to a rain garden; its main requirement is to be located where it collects the most water run-off. Observe where water drains naturally in your yard. If it’s absorbed and does not pool for long periods of time, you may have found your rain garden spot This can be near the discharge of a downspout, but to prevent moisture problems from developing gardens need to be located at least 13 feet from homes and septic beds.

“It is important to consider the volume of the rain garden in relation to how much runoff water will flow into it”, Maxemuck cautions. Rain gardens should only hold storm water for a maximum of two days; they are not ponds designed to collect and hold water. “If water stands longer than two days you may need to make the garden larger or amend the soil. Soil is critical; it must have good drainage properties and high organic matter.” Maxemuck recommends using peat moss or cocoa fibre to create a well aerated, porous soil with good water retention properties to help plants survive periods of drought. Clay-based soils offer poor drainage creating pond-like conditions. While C&S Gardens decided not to mulch their garden, they recommend considering a coco mulch to suppress weeds and to help prevent moisture loss.

Slope is another factor to consider when placing your garden. If the slope is too steep, erosion on the low lying side of the garden will occur; if the location is too low, you will have standing water and create a breeding ground for mosquitoes. Rain gardens also need to be levelled out; this can be achieved by creating a depression on the high side of the garden and a berm on the lower side. Information on how to determine the correct depth, size and location for your garden can be found easily online.

An unexpected variable encountered by Maxemuck was the need for irrigation in the rain garden during Manitoba’s hot summer months. “When I began researching rain gardens, I never considered how much water they would require in the dry periods of the summer”, he acknowledges. The situation was easily fixed by adding a couple of medium sized sprinklers to irrigate when required.

Creating your Beautiful Garden

The best time to create a rain garden is in the spring using healthy established plants from a local garden centre. Native perennial plants are often great choices for rain gardens as they have adapted to the local conditions. Another requirement is that they be able to thrive in temporarily wet or soggy conditions.

When making your selection, try to choose non-invasive varieties and plants with larger root structures which are helpful in removing toxins such as nitrates and phosphates from the water. C & S Gardens has successfully added birch, daylilies, liatris, echinacea, potentillas, dogwoods, hydrangeas, spirea, Karl Forrester and other grasses.

“Weeding, especially in the first few years while plants are becoming established, is important”, states Maxemuck. “When it does get wet, it can be difficult to weed for a long period of time, especially if you don’t have a mulch cover. It is important to help the rain garden plants get well established so they can compete with the weeds and develop a healthy root system to prepare them for the winter months.”

Other maintenance tasks include keeping the garden well watered in the first year, aerating the soil occasionally so that it does not become compacted, slowing down drainage, dividing and cutting back plants, and checking for signs of erosion. Once a rain garden is established it actually should require little maintenance. Now that is a thing of beauty!

Keep it natural

• Rain gardens attract wildlife, birds and butterflies and add an attractive and creative alternative to traditional lawn landscapes.
• Rain gardens have lower maintenance needs than lawns because there is no need to mow, fertilize, or water once established.
• Rain gardens can reduce storm drain overload and flooding if adopted buy a like minded group of neighbours.

Some of the native plants suitable for rain gardens.

• Potentilla
• Spirea
• Hostas
• Echinacea
• Columbine
• Native grasses

Article written by Tania Moffat for Manitoba Gardener magazine. Please visit www.localgardener.net for more gardening stories.