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Rain Gardens
Rain gardens are an excellent way of having a beautiful garden in your home that also contributes to reducing the amount of pollution in bodies of water such as rivers and lakes. This is because they absorb the rainwater run off that would normally go down the stormwater drain – water that is likely to contain chemicals due to lawn and garden care products and household products. Rain gardens can be as simple or as complex as you like, with or without the help of a garden designer. Read on to learn more.
What Rain Gardens Are
Rain gardens are gardens that have a specific purpose – to reduce the amount of stormwater runoff from the home. Water is funneled into the garden from the roof, driveway, or other large non-absorbent surface. Rain gardens are different to normal gardens in that they are bowl or saucer shaped, rather than being flat or raised like a traditional garden. Deep, loose soil is used specifically to collect and absorb rain that would otherwise run off from the property and/ to solve the problem of wet areas where water already collects.
Rain gardens generally use plants that are native to your area as these are the best adapted to the local weather conditions. Rain gardens have a ponding area but they are not ponds. Often, they are planted with wetland plants due to the moisture that travels through the garden but they are not a wetland.
Benefits of a Rain Garden
Rain gardens have several benefits, including but not limited to:
- creating a wildlife habitat
- making attractive feature like a water feature in the garden
- no need for fertilisers or chemicals
- absorbs the rain that would otherwise wash pollution down the stormwater drains
- removes many common pollutants in rain water
- they are very low garden maintenance
- contribute to natural groundwater recharge
Designing and Setting Up a Rain Garden
Rain gardens can be placed practically anywhere in the home. However, you should avoid areas that may house electricity, phone or gas lines. If you have a septic tank, locate the garden in a separate area to it. Always locate the garden away from the building’s foundations. Be aware that your property will already have an existing drainage pattern and it is easiest to take advantage of this when creating your rain garden. Look for the natural channels of water runoff and for low spots where water collects naturally.
If you don’t like the natural low areas in your garden or they are unsuitable, you can create a new area simply through excavation. Ensure that you will be able to get rainwater to flow to this location, either directly or by using pipes. If you have a sloping block, it is a matter of creating a “scallop” or terrace that will collect water. Never build your rain garden underneath a tree, as they are already very efficient at absorbing rainwater.
Ensure that your soil drains well. If it is mostly clay, you will likely have to add sand and compost to improve the drainage. To check the drainage rate of your chosen area, it is simply a matter of digging a hole approximately a foot wide and a foot deep. Half fill it with water and see how long the water takes to drain. It should absorb at the rate of one inch per hour.
The rain garden needs a ponding area – this is simply a dip in the middle for the water to collect for absorption. The standard depth for the dip is six inches. If water absorbs extremely slowly, make the dip shallower. If it absorbs quickly, you can afford to make the dip deeper. Be sure that the dip is saucer-shaped, and not bowl-shaped to ensure that the water can spread out as it absorbs.
There is no need to worry about mosquitoes in a rain garden. With a correctly built rain garden, all water will have absorbed into the soil within 48 hours – not enough time for mosquitoes to breed and hatch. As stated before, native plants are the best to use in a rain garden, but you can also use non-native plants. Mulch is recommended for most rain gardens as it keeps the garden moist and discourages weeds.
Plants for Rain Garden
You can get many of the plants for your rain garden from your local nursery or garden supplies store but other plants may need to be sourced from native or specialist nurseries. Other options include transplanting plants from a different area of the garden, or sourcing plants from your friends. Never take plants from the wild.
Native plants are the best option for a rain garden as they are already optimally adapted to the specific weather conditions found in your area. As well, they attract local wildlife. Because native plants have deep root systems, they increase the ability of the soil to hold water and help to prevent erosion.
It is important that you choose plants that will suit the location of your rain garden. For example, plants that need full sun will soon die off if your rain garden is located in a shaded spot. Some plants have specific requirements when it comes to the soil. Rain gardens have three very distinct zones – very wet, wet to dry, and dry. If your plant isn’t happy in one zone, move it to another and see if its condition improves.
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