The rain that is held in a rain garden is only temporary, and will effectively soak and drain water within 48 hours. So if you’re worried about increased mozzie activity in the garden, there’s no need to!
Is rain runoff bad for the environment?
When it rains, rain runs off surfaces that are full of chemicals and pollutants. This contaminated water is then collected in stormwater drains and sent untreated to rivers, oceans and natural water systems. If it rains an exponential amount, or rainfall is higher than average in a year, then stormwater can be quite toxic to natural environments.
This is why rain gardens should be built as much as possible, both in public, like Sydney council has, and in private backyards and gardens. Reducing the toxicity in rainwater runoff with a garden can help keep our water systems clean and healthy.
How to build your own rain garden
Building your own rain garden is quite a simple process. It is not the same as creating a traditional garden bed, and instead will need to be situated and built in a specific way.
A rain garden is usually positioned in an area of the garden that can easily catch roof and house water runoff.
It is best to have your rain garden towards the bottom of your yard, and preferably situated on a downward slope. Your garden should be created in a depression, meaning that you should dig down and remove 5-10 centimetres of soil. This is so rain can easily move toward this area and be caught in the garden bed.
Prepare your soil
Remove any plants or lawn already established in your chosen area. The best soil to use is clay-based because it has a lower percolation rate, meaning it allows water to drain slowly so it can catch contaminants and sediment easier.
If you don’t know what kind of soil you have, it may be best to complete a soil test. Loose sandy soil will need water-absorbing compost, which will allow your rain garden to be fully functional.
Your soil should be dug higher on the outside of the bed and sloping downwards into a depression in the middle of the rain garden.
Plant your rain garden
Your rain garden should have two different types of plants within it, natives and general plants on the inside, and marginal plants lining the outside.
While all of your plants should be tolerant of excess water, your marginal plants are a bit different, and should be able to withstand both extremes of moisture; lots of dryness when it’s not raining and excessive wetness when it is.
How big should a rain garden be?
A rain garden’s size is actually quite important. For this type of garden to be properly functional, it needs to be able to withstand the exact amount of rain runoff that is within your property.
For it to work, it is estimated that your rain garden is about 20% the size of your home’s roof, patio or deck that drains into it.
The best plants for a rain garden
A rain garden works best when it is made of plants that are from the surrounding natural environment. In our case, Aussie natives are the way to go! Australian native plants that like or tolerate clay soil include some classics like banksia, grevillea, dianella and bottlebrush.
On top of this, rain gardens should also have lots of grasses in them, as they have deep root systems that are perfect for water-absorption and drainage.
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