How to Make a Rain Garden

Wherever you are in the country, you’ll know that rainfall can cause damage when it comes down hard and fast.

Whenever it rains, water runs off the impermeable surfaces, including roads, driveways, and roofs, collecting pollutants as it goes in the form of dirt, oil, fertiliser, and so on. This stormwater runoff then enters the drains and flows into streams and ponds, leading to water pollution. This is the last thing you want if you have a pond or dam in your backyard that could become contaminated.

So, what can you do about this?

Well, a rain garden is a good start. It collects the runoff, filtering the water through the vegetation before it percolates into the soil. Sounds great, right? All that’s left now is to build one.

What Is a Rain Garden?

Generally, these gardens are small and filled with plants. The plant selection is actually crucial, because they need to be able to withstand extremes of moisture and nutrient concentrations. Storm water is high in nitrogen and phosphorus, so they should thrive on these nutrients.

Usually, rain gardens contain layers of sandy soil that can filter the pollutants from the water. So, the plants should also thrive in this soil type.

There’s usually an impermeable or sealed surface nearby, too, which collects the rainwater and funnels it into the garden. Plus, there’s a pipe below the soil that channels filtered water into the stormwater drain (or your dam).

Types of Rain Gardens

There’s more than one type of rain garden. This includes:

• Planter box: Positioned above ground to collect stormwater from a diverted roof down pipe. After filtration, the water flows into the stormwater system.
• In-ground: These use specially-designed garden beds in the ground to collect water from hard surfaces or nearby buildings. Again, it flows into the stormwater system after filtration.
• Vegetable: This is a sub-irrigated rain garden, which means the water enters at the base. It prevents vegetables from suffering in the submerged zone after heavy rain. There is less surface evaporation, allowing you to use the water more efficiently and grow vegetables.
• Tree pit: Captures stormwater runoff from the roads. However, this type only contains a single tree, making it ideal for built-up urban areas.

How To Create Your Own Rain Garden

Once you’ve chosen a type of rain garden to suit your needs and style, you can build your own in six easy steps.

Step 1: Choose the Location

Start by examining your yard, preferably after heavy rain. If there are any areas that have a little standing water, then this is the perfect place to put a rain garden.

Be careful, though, because it needs to be at least 10 feet away from your house. Ideally, put it down a slope from a downspout or water outlet so that water can flow into the garden easily. And aim for full sun or partial shade that your plants will love.

If you want your rain garden to collect rainwater tank overflow, too, then make sure it’s close by to your tank.

Step 2: Prepare the Soil

The next step is to prep the soil. You’ll need to remove all lawn, furniture, and other vegetation from the area first. If you don’t know what type of soil you have, get a soil test. Ideally, you want sandy or clay soils to allow for slow percolation and filtration. If you have loose, soft soil, add a water-absorbing compost topsoil.

Next, using a shovel, dig the area to a depth of 6 inches. It should have a gentle slope down from the edges to the deepest point at the centre. Use the soil to create a low berm on the lowest side, which will hold rainwater long enough for it to seep into the soil.

By the way, it’s important not to go deeper than 6 inches. If it takes too long for the water to percolate, you risk attracting mosquitos.

Step 3: Choosing Plants

All the best rain gardens have native plants, because they can help your local region thrive. However, you should also look for native plants from boggy, wet habitats like rushes and grasses, which tolerate heavy rainfall well. Plus, these plants have deep roots that will help the soil health.

While these should make up around half of your rain garden, you can also add other plants with different colours and textures to make it aesthetically pleasing.

Step 4: Adding Marginal Plants

Speaking of those, they are called marginal plants. These grow near the edge (margin) of a pond, which means they can tolerate a saturated or submerged zone but they don’t necessarily need it. They can also survive dry spells quite well.

Consider irises, cardinal flowers, and scarlet rose mallow for your rain garden.

If you’re unsure about what to use, your local nursery will be able to advise you on the best rain garden plants.

Step 5: Planning and Building

Once you have researched your garden, you can start to build it. This is more important if you’re using a planter box garden, for which you’ll need to construct your boxes and start to add them.

At this point, you can also determine if your garden needs a liner or other impermeable surface that will collect stormwater. You can also install the overflow pipe to drain excess water during particularly heavy storms.

Make sure you have a flow spreader at the end of your downpipe or rainwater tank, ensuring you can evenly distribute water flow and limit erosion.

Step 6: Designing and Planting

You can be as creative as you want with your garden. Space your plants as evenly as possible, and try to group them in a way that looks pleasing to the eye.

You can add other textures, too, such as mulch or gravel. And as a bonus, this keeps the moisture in. Avoid using bark or straw mulch, though, as it can float and wash back into the clean stormwater.

Some of your marginal plants should be drought-resistant. However, if it doesn’t rain, make sure you water your garden in compliance with your local water restrictions. Keep removing any weeds that pop up, too, and cutting back old, dead growth.

Once your rain garden is up and running, it should be more or less self-sufficient after the first year.

Top Tips for a Stunning Rain Garden

As long as you add native Australian plants to your rain garden, you won’t need to do too much maintenance. That said, here are my top tips for making your rain garden as beautiful and easy-to-care-for as possible.

• Gravel mulch can retain moisture and make sure your rain garden functions well.
• Weeding your rain garden until the plants have matured will protect them for years to come.
• Alongside adding a flow spreader, you can use strategically placed rocks to prevent erosion. These also make rain gardens look even nicer.
• Inspect your rain garden frequently and take effort to replace plants and repair erosion when necessary,
• Don’t drive over or walk on your rain garden, as squashing it can prevent it from working effectively.
• If it doesn’t rain, water your rain garden frequently.

Final Thoughts

Rain gardens are designed to capture rainwater and filter out bacteria and other pollutants, before the water flows into the stormwater drains and drainage system.

If you have a pond or dam in your backyard, you can even use a rain garden to filter the water and funnel it back into your dam. This is particularly good news if you have a pond teeming with fish and other aquatic life.